Tag: Nuke

Week 11: Motion Blur in Maya, Matte Painting in Photoshop, Nuke Comp, & Final Render

Post author By Nira Gonzalez Sanchez
Post date 24th June 2023
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This week, I researched pictures that I would use for my matte paintings in Photoshop to then implement the m in Nuke for my final comp. I also rendered again my scene from Maya with motion blur added.

Motion blur added in Maya render

I was not convinced about the way the render of the scene was looking, so I asked Marianna for help and advice. I explained that the image look too sharp and neat, and it did not look realistic at all as it was missing depth of field and some blur. Then she explained to me that in Maya I could really easily apply motion blur in my render settings (literally just need to tick an option), and Maya would add the motion blur and depth of field for me.

Mayan environment with motion blur

Matte paintings in Photoshop

For the sky matte painting, I took a sunset sky picture and using the ‘offset’ and the ‘stamp’ tools in Photoshop, I made an ‘infinite’ picture so the edge of this is not visible if applied in a sphere or a cylinder to recreate the environment background. The background mountains were made like this too, however, in the rest of the matte paintings I only removed the the sky of the pictures.

Compositing in Nuke and SFX in After Effects

In Nuke I added those matte paintings previously made in Photoshop. I added the sky as a sphere texture so it looks more realistic and has more sense of depth. The background mountains were added to a cylinder was they were going to surround the whole scene (as the camera movement rotates through all the scene, this needs to be visible from all the angles). The foreground mountain and the extra rainforest bits were added as projections to simple cards since they constitute small sections only so do not need curved surface. To give more depth to the scene, I added some highlights and shadows to the mountains using rotoscoping. Lastly, I decided to search a clip of a waterfall to add it to the back of the scene so the river position has sense and continuity. Since the cards of the waterfall were giving me problems as they would get in the middle of the camera movement and they would show were the should not, I set their lifetime until only farm 400 so they disappear after. I also had to colour correct the water if the waterfall to match the colour of the river and I also gave the sky an orange/yellow tone so it matches the sunset sky’s colour.

Mayan Environment Final Comp

Mayan environment final comp

Tags Compositing, Matte Painting, Nuke, Photoshop, Rendering

Advanced & Experimental Group

Week 4: Spaceship WIP 1 & Matchmove Task Reviews, & Spaceship WIP 2 Model Detailing

Post author By Nira Gonzalez Sanchez
Post date 7th May 2023
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This week I focused on finishing the matchmove task with all corrections required and also tried to finish the spaceship model ready for texturing.

Matchmove task

I had a second 1-to-1 session with Dom and asked him about how to export from Maya to Nuke and how to correct camera alignment in 3D Equaliser or Maya. In 3D Equaliser, I missed to set the point of origin and to set the ground points. Also, I needed to align my camera horizon so everything is level to the footage. Once this was corrected, ,I exported it to Maya and realigned the cards and cones of 3D scene. Then, I exported cards, cones, and camera separately in .abc (alembic) as explained by Dom. As I already had the scene previously set before these corrections, I replaced the camera exported from Maya in the Nuke file exported from 3D Equaliser, then connected the cards and cones as geometry in the ‘Scene’ node, added a red constant and some lighting to give some colour and contrast to the cones, and finally redistorted everything together. I finally exported the final matchmove and uploaded it to FTrack for assessment.

Final matchmove

Spaceship WIP 1 review and further modelling of WIP 2

This week I tried to finish the spaceship model to get it ready for texturing. I added more details such as windows on the sides (adding edge loops and extruding), two extra engines and wings in the sides, changed the bottom part and added extra details so it looks like a boat, and lastly, I added some extra details in the top of the spaceship so it looks like the top fin of a fish. Most of the more organic design ini this model was made using ‘Curves’ to make the shape I wanted and then with a disc, extruding following curve made. My main reference for the added features is the following:

Reference picture (Michal Matczak, 2012)

Once I finished with the model, I exported a 360° view and took some wireframes screenshots as requested in my first FTrack review of my first model version.

Final model 360° view – Maya render

References

Matczak, M. (2012). artwork, airships, steampunk airship, steampunk, aircraft, industrial, fantasy art, smoke, rocks, cave, Michal Matczak, concept art, lights, Zeppelin, HD phone wallpaper (online). Available at: https://www.peakpx.com/en/hd-wallpaper-desktop-kdvbs [Accessed 22 April 2023]

Tags 3D Equaliser, 3D Modelling, Matchmove, Maya, Nuke, References

Advanced & Experimental Group

Week 3: Group Project Matchmove Practice & Spaceship WIP 1

Post author By Nira Gonzalez Sanchez
Post date 30th April 2023
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This week, we received the group project live action footage so we could make the matchmove in 3D Equaliser, Maya, and Nuke. I also started modelling the spaceship for the group project.

Matchmove task

I started to track the live footage we were given in 3D Equaliser, trying to follow the steps we learnt last week. This was a bit challenging as the floor of the footage had a lot of reflections and it was difficult to keep the tracker on place. Also, before tracking, I denoised the plate in Nuke so I could get a clearer image for tracking. I only tracked the green marks added in the scene initially, however, after my 1-to-1 session with Dom, he clarified that the green marks were only references and that I could add more tracker points anywhere I needed (the more tracker points the better results I could get later on). Therefore, I added more tracker points to then reconstruct the scene in Maya and added red cones on every single tracker point.

Matchmove playlist in Maya – WIP

I was a bit confused on how are we supposed to export the geometry in Maya and the process after this in Nuke, so I will book another session with Dom for next week.

Spaceship WIP 1

For my spaceship model I made some sketches on Procreate app first and then some more hand-drawn sketches while discussing with my group the style approach we were going to follow.

Initial spaceship idea (sketch in Procreate)

After figuring out how the spaceship would look like, I start to 3D model it in Maya directly as I will also have a better idea of dimensions.

We were also asked to submit next week our first model WIP to FTrack so I put together some render views.

Also, Roos created a group Padlet board where we will be adding the progress of each team member’s tasks and where we could give feedback and add notes too.

Tags 3D Equaliser, 3D Modelling, Concept, Matchmove, Maya, Nuke, Sketch

Advanced & Experimental Advanced Nuke

Week 10: Term 3 Group Project Brief, & Homework Q&A

Post author By Nira Gonzalez Sanchez
Post date 19th March 2023
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In this lecture, we were introduced to term 3 group project and reviewed the devil comp homework.

Term 3 group project brief

The deadline of the term 3 group project would be on the 29th June 2023 (8 weeks duration) and we will have this group project and a personal project too.

We will have to create a futuristic spaceship room based on any of these 3 themes: steam punk, cyber punk, or low-fi sci-fi. This project will simulate the work pipeline of a professional VFX studio.

We will have the live footage of a corridor/room and we will have to comp it with CG elements to make it futuristic. We will have to choose our group and each team member will have to pick a roll. We will need to organise the project with our team members, taking care of:

Research of ideas, and moodboard build up.
Planning of assets that are going to be needed.
Planning each team member’s task weekly.

Every week, this project will be reviewed and notes will be shared that will need to be followed for the next review. We will work with F-track programme to be able to see notes, calendar, objectives, etc. Every time we present assets, we will need to present them in detail, showing the topology, texturing, and lighting. Also, Dom Maidlow (CG Generalist) will be teaching us how to track plates and how to import into Nuke.

The final outcome required would be a 10 secs animation, and it will have to follow the requirements stated in the brief provided.

Devil comp homework

In this comp, we were asked to add texture and elements to a live footage of a devil man. I researched some skin texture that shows like scarring or open wounds and I found a dragon-like texture that if graded and colour corrected could look like what I had in mind. I also wanted to add like a wound with surgical stitches to the closed eye, and like satanic tattoo in his forehead. Also, I added some fire in the horns, and for the environment, I found a video with smoke, fire, and sparks.

For the face texture, I ‘Roto paint’ part of the face to get rid of the hair on one of the sides. Then I also added a dragon-like texture to add a more interesting look. I also covered one of the eyes and added a stitches texture on top. Then I added a ‘Vector Distort’ so the alphas created with the textures are warped following the movement of the face.

For the forehead tattoo and the fire in the horns, I used 3D tracking of the man’s face and created 3 cards taking as reference points the middle of the forehead and to top tips of both horns. Then I projected the tattoo texture and the fire footage on those cards and colour corrected them. Since the video of the fire was flat and the head of the man was moving side to side, I had to adjust the rotation of the card adding some keyframes when the head rotated.

Lastly, I added some sparks footage on the foreground, and colour corrected the whole comp.

Skin clean-up, texture, and stitches effect

Final comp

References

Algol, M. W. F. This 666 Devil Satan Pentagram Black (online). Available at: https://www.nicepng.com/ourpic/u2q8t4q8e6o0e6q8_666-devil-satan-pentagram-black-freetoedit-michael-w/ [Accessed on 19 March 2023]

Ektoplazm. Over 50 Skin Textures Free Download (online). Available at: http://www.psd-dude.com/tutorials/resources/over-50-skin-textures-free-download.aspx [Accessed on 19 March 2023]

Ezstudio. Orange cloud smoke Fire sparks rising up Free Video (online). Available at: https://www.vecteezy.com/video/5160760-orange-cloud-smoke-fire-sparks-rising-up [Accessed on 19 March 2023]

Videezy. Fire Stock Video Footage (online). Available at: https://www.videezy.com/free-video/fire?page=5&from=mainsite&in_se=true [Accessed on 19 March 2023]

Tags Comp, Devil, Group Project Brief, Nuke

Advanced & Experimental Advanced Maya

Week 9 & 10: Loop Animation Comp in Nuke

Post author By Nira Gonzalez Sanchez
Post date 14th March 2023
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In these two weeks, we could dedicate the lectures to polish and finish the loop animation and to ask all the questions we had about it.

After I finally got to render all layers, I put them on together on Nuke. I order to do the shadows, I duplicated the main model and projected it on a card perpendicular to the first main model. Then, I colour corrected, desaturated, and blurred this projection to match the shadows from the background. Following on, I thought that the neon ring if the dome looked too flat, so I decided to add some fake neon effect by adding glow, filter erode, and edge blur to create this diffused yellow light, and then duplicated this to create the interior white light of the neon (just desaturated the colour so it looks white). Since this neon half ring is supposed to be reflected in the metallic edge of the model platform, I also added some fake reflections a radial node that has been rotoscoped and graded accordingly (also added some edge blur and blur to soften core and edges of reflection). Moreover, the space texture from the inside dome was not too visible, so I rotoscoped the area where this texture is supposed to appear and added the texture manually instead of exporting it again. I also graded it so it did not show too much detail (that was the previous problem I tried to correct in Maya but for some reason it did not render as it was supposed to). Lastly, I also considered that the background look too flat, so I added some more pronounced shadows on the sides by rotoscoping the sides I wanted the shadows and adding some edge blur, blur, and grade to get the shadows colour.

Final animation with extra lights and shadows in Nuke

Final comp without SFX

Since this was supposed to be an oddly satisfying loop animation, I also decided to include a relaxing background music to improve to the experience. The final looping videos were edited in After Effects.

Final Video with SFX

I enjoyed this project so much and I think I got more confident in my modelling and texturing skills with it. I also learnt the different ways to render a comp to then comp it by layers in Nuke, and After Effects, meaning that I do not need to finish everything in Maya, and I can take advantage of different programmes that are specialised on different aspects, to achieve better results. I also got more confident with node editing in Nuke as it has always been a bit challenging and intimidating for me, so I feel like this project has helped me expand my creative, technical, and project management skills in many areas.

Tags After Effects, Compositing, Maya, Neon Effect, Nuke, Shadows, Sky Texture

Advanced & Experimental Advanced Nuke

Week 9: Nuke Homework Q&A Session

Post author By Nira Gonzalez Sanchez
Post date 12th March 2023
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We dedicated this lecture to asked all the questions we had about what we have seen in this term and our weekly homework and projects.

Hero shot green screen removal homework correction

In this comp I had an issue getting the finer details of the girls hair when removing the green screen and comping with the forest background. Also, the snowflakes I keyed to add in the foreground of the scene were barely visible. In order to take the hair details, I had to take a ‘IBK colour’ node and pick the darks and lights of G (green colour) so it selects as much detail of the hair as possible. I can also use ‘Filter erode’ to remove noise and then add ‘patch black’ (like at 20) to remove black part. Then, I can add a ‘IBK gizmo’ set to green, and then link ‘fg’ to green screen plate, and ‘bg’ to background plate (so it takes background features). Then, I can tick ‘use bkg luminance’ in the ‘IBK gizmo’ node, so it takes the background luminance, and tick ‘use bkg chroma’ so it takes background colour too. I can then ‘Merge (over)’ the ‘A’ link to the ‘IBK gizmo’, and ‘B’ link to background. This will take all the details of the hair from the green screen and add it to the luminance of the new background.

Regarding the snow problem, I was taking the luminance with ‘Keyer’ node from the original plate, and I had to connect it to the ‘Transform’ node instead so it takes the correct aspect ratio. Then, every time I ‘Premult’, I always need to use ‘Merge (over)’, so I changed to this node. I can also add more or less effect with ‘Multiply’ node.

Final green screen removal scene

Final green screen removal scene – alpha

Markers clean-up homework correction

I asked the professor for the distortion I was getting from the smart vector and he confirmed to me that the problem was that the node was affecting the whole image. So in order to correct it, I had to add a ‘Premult’ to the ‘Roto paint’ and add a ‘Framehold’ again (before the ‘ST map’), so the distort only affects the alpha created with the ‘Roto’. Also, I need to improve ‘Roto paint’ using the techniques to control light changes.

Smart vector technique for marker removal

Final result

Garage comp homework correction

In this comp I had the issue with the shadow being cast on the wall hole. To remove the shadow from the wall hole, I need to take the previous roto made for that wall and ‘Merge (stencil)’ in the shadow part (between ‘Blur’ and ‘Grade’ nodes). Then, before this ‘Merge (stencil)’ node, we add an ‘Invert’ node so the roto alpha only takes the hole instead of the wall. To correct some bits that are outside this previous roto and that now are showing as this has been inverted, we make a quick ‘Roto’ that selects the area we want to keep (the hole in this case), we adjust the position of this ‘Roto’ in several frames, and then we ‘Merge (mask)’ to ‘Invert’ node (‘B’ connection). Lastly, we make the edge of the roto less crisp adding ‘Edge blur’ so it softens it.

I also fixed the back objects as they were looking too dark and the smoke effect was not affecting them so it did not look realistic. I then desaturated the colours adjusting their ‘Grade’ nodes and then added a ‘Merge (over)’ from the smoke card block to these objects.

Roto with merge (mask) to only keep hole roto

Final garage comp

Tags Homework, Nuke, Q&A

Advanced & Experimental Advanced Nuke

Week 8: Markers Clean-up Techniques & Homework in Nuke, & Final Garage Homework Review

Post author By Nira Gonzalez Sanchez
Post date 5th March 2023
No Comments on Week 8: Markers Clean-up Techniques & Homework in Nuke, & Final Garage Homework Review

In this lecture, we learnt how to remove markers from a character’s face in a live footage scene, and how to add texture and corrections that follow the movement of the character.

Degrain/Regrain techniques

Before starting with markers removal from a live footage shot, it is important to degrain our footage so Nuke can read and detect better the pixel information when adding different nodes for cleaning up or tracking techniques. If we use this, then we will need to regrain the plate once we have finish all our changes, so all added elements have the same grain texture and it looks like it has been filmed all in one shot with the same camera and light conditions.

Simple degrain. We can denoise plates with ‘Merge (minus)‘ followed by a ‘Merge (plus)‘.
‘F_ReGRain’ node. This is an alternative to regrain node and it is only available in NukeX. It is more precise than a simple regrain, since it shows less of the patches added for clean up plates.
‘DasGrain’ gizmo. This gizmo can be downloaded from Nukepedia where there is also a tutorial on how to use it. We will plug the ‘DasGrain‘ to the original plate and to the denoised plate. Then we plug a ‘Common key‘ gizmo to ‘comp‘ and ‘mark‘ links in ‘DasGrain’. In ‘DasGrain’ node settings, we can set ‘output‘ to desired one (it has different outputs for QC). In the ‘replace‘ tab, we can select the area we want to scan (usually the darkest area), then select ‘activate‘ and then ‘analyse‘. This gizmo is being newly used across VFX companies due to its efficiency and reliability.

Patch changing light techniques

When adding patched to clean up marker in our plate, we need to take care of light changes as the patch could be too obvious:

First, we can try to correct lighting manually by using a ‘Unpremult‘ node, then ‘Grade‘ by hand in the needed keyframes, and then ‘Premult‘ back. This technique is not recommended as it is time consuming.
Divide/multiply technique. ‘Blur‘ image (add a lot of blur), then clone the ‘Blur‘ node, and add ‘Merge (divide)‘ to merge both ‘Blur’ nodes. Lastly, ‘Merge (multiply)‘ with background.
Image Frequency Separation technique. We use ‘Slice Tool‘ gizmo to analyse a specific area of the plate (a face with markers for example), and all frames too (separated gizmo). Then we ‘Blur‘ to see low frequency of image and ‘Merge (from)‘ node to see high frequency. With this, when cloning area with ‘Roto paint‘ to clean markers, we are going to paint only low/high frequencies so the light is not affected (only gamma). This technique is used so light changes do not affect the patched area. With ‘Laplacian‘ node, we could get the same result too. We first need to link with ‘Merge (plus)‘ node to bring back the light and the colours from the original plate, then we ‘Rotopaint’ the part we want, followed by a ‘Blur‘ to add/remove the quantity of light required. Alternatively, we could also ‘Blur‘ and ‘Multiply (divide)‘ to see and correct different values, to then we ‘Merge (multiply)‘ to merge back (like mentioned before).
Interaction patch technique. Add patch with ‘Roto paint’ with ‘match move‘, then scan original plate with ‘Transform‘, ‘Copy (alpha -> alpha)‘, and ‘Premult‘. Then ‘Merge (multiply)‘ with plate, ‘Regrain‘, and ‘Merge (over)‘ with main plate.
‘Curve tool’ node. This is used to add/remove info to the plate (for example, to correct flickering of image). First we start by cropping the info we want by adding ‘Curve tool‘ node, selecting an area, setting ‘curve type‘ as ‘max luma pixel‘ and then click ‘go‘ so it starts to analyse the area. Then, in ‘max or min luma data‘ we click on the icon at the end and then right ‘click + copy + copy links‘. Then we go to ‘grade‘ and ‘paste + paste absolute’ on ‘lift‘ (shadows or min luma data) and ‘gain‘ (luminance or max luma data).
‘Roto’ and ‘Transform’ technique. We start with ‘Transform‘ node, followed by a ‘Roto‘ of the part we want, and a ‘Track‘ of the roto. Then we ‘Blur‘ the roto as alpha, ‘Premult‘, and ‘Merge (over)‘ with main plate.
Clone patch technique. First we denoise the plate so we can ‘Track‘ the markers properly (1 track per marker). Then we copy translate x and centre x to ‘Rotopaint‘ node. We do the patch with clone tool and add ‘Roto‘ over cloned area. Finally, we ‘Filter erode‘, ‘Blur‘, ‘Regrain‘, and ‘Merge (over)‘ to main plate.
‘Premult’ and ‘Unpremult’ for paint technique. First, ‘Denoise‘ plate and ‘Track‘ marker. Then copy ‘Roto‘ over marker. ‘Invert‘ roto/mask (like a hole), and ‘Merge (mask)‘ to ‘Shuffle‘. then ‘Blur‘ slightly and link as a mask to ‘Edge blur‘ node which previously was linked to ‘Merge (mask)’ node. Then we ‘Unpremult‘, ‘Copy (alpha -> alpha)‘ from ‘Blur‘ to ‘Premult‘. Lastly, we ‘Regrain‘ (linked to original plate), ‘Premult‘, and ‘Merge (over)‘ to main plate.
‘In Paint’ technique. It is nearly the same as the previous technique but, instead of inverting the roto and blur it, this time we use ‘In paint‘ node, which can be tweaked to make the patch blend in.
‘UV map’ technique. When using ‘Expression‘ node, R and G channels (X and Y coordinates) have identical values, and just B value is 1, which has no effect on what ST/UV images do. With ‘Expression‘ node, we can ‘Roto paint‘ specific details such as motion blur or warp of an image, and the we connect ‘ST map‘ node to plate. We could also use ‘Grid warp‘ node, but since this is a really heavy tool, it is recommended to avoid this if no needed.
Vectors technique. As usual, first we ‘Denoise‘ the plate, to then use a ‘Smart vector‘ node. This node could work fine with the default settings, however, it is better to increase ‘detail‘ to achieve a better result and to have less problems with image warp later on. Then we can export this with ‘Write‘ node since smart vectors are really heavy and could slow down the preview. Separately, we remove the markers with ‘Roto paint‘, ‘Filter erode‘, and ‘Blur‘, and we also add a ‘Frame hold‘ node in the reference frame where we are doing the cleaning up. Then we add a ‘Vector distort‘ node that will track the movement of the markers (set ‘output‘ to ‘warped src‘ in this case) following the smart vector map created previously, and then we add a ‘Copy (motion -> motion)‘. Apart, we add a ‘Vector to motion‘ node to add motion blur to the movement of the markers and the we link to to the ‘Copy’ node we added before. Then we add a ‘Vector blur‘ node (with the ‘output‘ as ‘result‘), we ‘Regrain‘, ‘Premult‘ and ‘Merge (over)‘ to main plate. We could also use an ‘ST map’ after the ‘Vector distort’ and in the last one, add ‘output’ as ‘ST map’ instead. This way is better than ‘warped src’, since ‘ST map’ is lighter. Smart vectors can also be used to add texture.

Homework – Face markers clean-up

This week’s homework was to remove the markers of a live footage shot of a girl moving her face. I first tried tracking the markers with a regular ‘Tracker’ node to then link it to the patches made on each marker. This technique is quite straight forward for time consuming since the ‘Tracker’ was also failing to track properly so I had to move the tracker point manually to the correct spot in most of the frames. Also, some of the patches are visible when the girl looks to the sides.

I also tried a different technique, using a ‘Smart vector’ node this time. This technique is really quick if it works fine, however, I am struggling with the distortion of the face when the girl moves her head.

I think I may be doing something wrong as it is distorting the whole image and not just the patches added. I will have to ask Gonzalo in the next class (final result added on Advanced Nuke – Week 9 post)

Final Garage Comp

Since this week I could not go to class in person as I was ill, I did not have the chance to ask for the questions I had regarding the shadows in my garage comp. Therefore, I emailed Gonzalo with a version of my comp attached and my question regarding the shadows being too harsh, and he sent me back a solution to this issue. It looks like I had to add another the ‘Shuffle’ + ‘Blur’ and mask link it to another ‘Grade’ node connected to the main plate, as shown below:

Garage Comp

However, I still got the issue of the shadow casting on the wall hole. I tried to add a ‘Merge (stencil)’ node using the previous wall roto I had, however, it was not working as it was cropping the whole wall and not just the hole. I will ask the professor next week about this (final result added on Advanced Nuke – Week 9 post).

Tags Markers Clean-Up, Nuke, smart vector, Tracker

Advanced & Experimental Advanced Nuke

Week 7: Despill Corrections Tips, Creating Gizmos in Nuke, & Garage Homework WIP

Post author By Nira Gonzalez Sanchez
Post date 26th February 2023
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In this lesson, we learnt to make despill corrections when removing green/blue screen, also we saw how to create our own personalised gizmos in Nuke, and lastly, we asked questions we had related to our garage homework WIP.

Despill correction tips

When keying to remove green screen and then remove saturation, we can roto some parts of the shot and then link this roto to ‘invert’ node so the despill does not affect that specific part.
We can also correct edges with ‘IBK Colour’ node set to ‘blue’ colour only, then we add a ‘Grade (alpha)’ so it only affects the alpha, then we correct the edge with ‘Filter Erode’ and ‘Blur’, and lastly, we ‘Merge (screen)’. We could also add an ‘Edge Blur’ to soften sharp edges and a ‘Clamp’ to make sure all merged alphas value is 0.
With ‘Add mix’ node, we can merge alphas and can set how much alpha we want to see.
Additive key: after a ‘Merge (minus)’ we desaturate and grade, and then we add a ‘Merge (plus)’ to ‘Constant’ node with the green colour as reference.
Divide/Mult key: we rerplace spill with ‘Merge (divide)’ from both the chroma plate and the chroma reference plate, to then ‘Merge (multiply)’ with the background plate.
When the green/blur screen have different luminance along the shot, we correct it taking a ‘Constant’ node with the darkest part colour of the green/blue screen connected to a ‘Merge (average)’ node so we create a ‘Constant’ with a colour with the same luminance. Then we ‘Merge (minus)’ with a ‘Keylight’ for despill.
We could add a ‘Light wrap’ node to add a light glow around specific areas. We will ‘Merge (plus)’ to the background in this case.
An inverted matte can be used to delete light from an outside edge. We just ‘Invert’ the matte, then ‘Roto’ the required parts, and ‘Merge (mask)’ to the matte. We could also add a ‘Grade’ node with a mask link to this ‘Merge (mask)’ node so we colour correct that specific edge.

How to create gizmos

First, we select the nodes we want in the gizmo and group them (ctrl + G). Then in the creed node options, we click the ‘edit’ button and drag and drop the features that we want (controllers). We can label these controllers by clicking on the little circle next to it. We then link each controller with the node controller (hold ctrl + drag and drop from main node to grouped node).

Green screen and despill homework

The homework for this week was to remove the green screen of a hero shot girl scene and add it to a snowing forest background, as well as add some of the background snow to the foreground.

First, I use a ‘Keylight’ node set to detect just the green colour and ‘Merge (minus)’ to the main plate to only see the greens of the shot. Then I aded a ‘Roto’ to the eyes of he girl and ‘Invert’ it linked as a mask to he saturation node to preserve the little amount of green of her eyes. Then I linked a ‘Merge (multiply)’ node from the background plate to the foreground plate to take some of the luminance of the background to the girl. This also was ‘Merge (plus)’ to the foreground to add that luminance to the scene.

Separately in another block of nodes, I used an ‘IBK Colour’ node to key the green screen of the foreground. Then I desaturated it, and added another ‘Grade’ with ‘Filter erode’ and ‘Blur’ and ‘Merge (Screen)’ to previous ‘Grade’ so I get more details and luminance from the girls hair. Then I ‘Copy’ this alpha to the main foreground alpha, to then ‘Add mix’ these alphas to the background plate.

In the background plate, I used a luminance ‘Keyer (alpha)’ node, to select only the colour of the snowflakes falling. then I ‘Copy’ this alpha to the background plate and also ‘Premult’ to create the alpha that will be added to the foreground with ‘Merge (over)’ node.

Finally, I colour corrected and graded the overall result and rendered the alpha and the final comp.

Final hero shot

Alpha version

I am not totally sure about the amount of hair detail that is visible in this version so will ask the professor on the next class (corrected version added to Advanced Nuke – Week 9 post).

Garage homework WIP

Lastly, I asked Gonzalo about my issue with the shadows not showing in my garage comp. He found out that the ‘Grade’ node that was after the ‘Shuffle’ node to create the shadows alpha, had ‘black clamp’ option ticked, so I had to deselect this and select ‘white clamp’ option instead so the blacks of the shadows started to show. However, despite the shadows were finally showing, I feel like they are too harsh and saturated and I could not figure out how to soften them. I tried to grade them and desaturate them but still looked to black and unnatural to me. Also, the hole in the wall is receiving the shadow from the chain hang on the wall and it looks like there is a plane receiving this shadow. This issue is due to the card added on that wall to receive the cast shadow so I tried adding a ‘Merge (stencil)’ from the roto I have from that wall but it did not work for some reason. I will have to ask Gonzalo in the next class.

Tags Despill, Gizmo, Keyer, Nuke

Advanced & Experimental Advanced Nuke

Week 6: HSV Correction Process & Chroma Key in Nuke, & Garage Homework WIP

Post author By Nira Gonzalez Sanchez
Post date 19th February 2023
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In this lecture, we learnt how to correct Hue, Saturation, and Value (Luminance), and how to use chroma key in Nuke. We also reviewed our garage comp WIP.

The meaning of HSV break down is the following:

H – Hue. Applies to colour (R, red value)
S – Saturation. Applies to the intensity of the hue/colour (G, green value)
V – Value. Applies to luminance or brightness (B, blue value)

This is important to understand as the quality of a HSV correction in a comp depends of our understanding of this elements.

When making hue corrections, we can use the ‘Hue correct‘ node to mute (colour channel as ‘0’), suppress (suppressed colour channel as ‘0’), or desaturate (saturation channel as ‘0’) a specific colour. This is useful for example to remove a green screen with the green colour channel suppressed.

With the ‘Keyer‘ node set with ‘luminance key‘ operation, we can determine the quantity of luminance we want to remove from the alpha of an image (black parts are not affected, but white parts only). We could also set the operation for ‘red keyer’, ‘blue keyer’, etc. Then we could ‘shuffle’ to green only, for example, and the colour correction will only affect saturation. We can also use this node to add, subtract, and multiply elements:

We can remove a colour channel with a ‘Merge (minus)‘ node linked to the colour we want as background and the colour we want to remove.
With ‘Add (Math)‘ node we can add colour when linked to a ‘merge (minus)’ node.
We could also use ‘Roto‘ to add or remove colour of a specific area.

Texturing can also be made with a ‘keyer (luminance)‘ so we use the alpha of the texture to adjust the luminance. Then this would be blurred, graded, and merged (minus). Moreover, we could also use the keyer to add noise or denoise in certain areas.

Some extra nodes and techniques can be used to create some effects that will give more credibility to our image:

‘Volume rays‘ node. Used to create rays effects or motion effect.
‘Edge detect‘ node. To select the edges of an image’s alpha and colour correct those specific edges.
‘Ramp‘ node. To balance image with gradient (used with ‘Merge (minus)’ node).
To add a new channel in ‘Roto’. We create a new ‘output’ (name it, click ‘rgba’ and ‘ok’), so when adding different features like blur or grade, we can link that change in the node and it would only affect that new channel created. We could also use ‘Add (channel)‘ node instead, select the channel as ‘Matte’, and choose that it will only affect to certain colour. We could also add a ‘Rotopaint’ to this and add shapes linked to different channels.

We can use keying nodes and techniques for chroma key such as:

‘IBK‘ (Image Based Keyer). We can subtract or difference with this node. It is considered the best option for getting detail out of little areas like hair or severely motion blurred edges:
- ‘IBK colour‘ node. Frame by frame rebuilding background taking blue or green colour.
- ‘IBK Gizmo‘ node. Can select specific colour.
‘Chroma key‘ node. First we can unselect ‘use GPU if available’ if our computer starts lagging. This node works better with evenly lit screens and with more saturated colour. We could use it for despill, but better not to as what we want is to extract the alpha.
‘Key light‘ node. This is used for colour spill.
‘Primate‘ node. This is a 3D keyer that puts colour into 3D colour space and creates a 3D geometric shape to select colours from it. We first select ‘Smart select background colour’, we pick a colour while holding ctrl+shift, then we change to ‘Clean background noise’, and holding ctrl+shift, we pick the colour parts that are still showing in the alpha (and need to be removed). We could also click on ‘Auto compute’ to create an automatic alpha and then retouch areas back to alpha with ‘Clean foreground noise’.
‘Ultimate‘ node. This is used for fine detail, and to pull shadows and transparency from the same image.
Green/Blue despill technique. We create an alpha with ‘Keylight’ node and ‘Merge (difference)’ to plate. Then we desaturate the background with a ‘Colour correct’ node and ‘Merge (plus)’ with the ‘Keylight’ node. Then we ‘Shuffle’ and put ‘alpha’ in black. Additionally, we could reduce the light in the background (saturate and grade) with ‘IBK Gizmo/Colour’. There are some companies that have created their own gizmo with all the required presets to despill.
‘Edge Extend‘ node. This is used to extend edges so we can correct the darken bits (smoother edges and not as pixelated).

A standard chroma key process would have the following steps:

Denoise plate
White balance
Alpha pipe
1. Core matte
2. Base matte
3. Hair matte
4. Gamma matte
5. Edges alpha
Despill pipe
1. Edges despill (specific parts)
2. Core despill (overall)
QC
Light wrap
Regrain alpha and background
‘Addmix’ to link alpha and background

Green screen homework

The homework of this week is to improve the garage comp and to make a chroma key of a sequence provided by the professor so we can put in practice all the techniques learnt in class.

Denoise, white balance, core matte, base matte, and hair matte

Final green screen replacement

Alpha version

Garage comp WIP

Regarding my garage comp work in progress, the professor also sent us a Nuke comp with examples of how to set lighting and shadows with projections or geometry. I tried to follow the example with the geometry as I only had 3D objects in my comp, however, I had some problems with the shadows as they were not showing at all in the final result. I could see them showing in the alpha created with the ‘shuffle’ node, however, since I could not see them in the final output, I guess I have something wrong with the ‘merge’ node or with the concatenation of the comp. I will try to ask Gonzalo in the next lecture about this. I also added a texture to the right wall so it looks like it was previously painted but the paint is being degraded and it is peeling off the wall. I roto the part of the texture that I was interested in showing and then used a projection of the texture on a card in a 3D scene.

References

Cini, A (2023). Color Theory HSV or Hue, Saturation, Value Brightness Illustration Chart Vector (online). Available at: https://www.dreamstime.com/color-theory-hsv-hue-saturation-value-brightness-illustration-chart-color-theory-hsv-hue-saturation-value-brightness-image237125365 [Accessed 19 February 2023]

Tags Chroma Key, Green/Blue Screen, HSV, Keyer, Nuke

Advanced & Experimental Advanced Nuke

Week 5: 3D Compositing Process in Nuke & Garage Homework WIP

Post author By Nira Gonzalez Sanchez
Post date 12th February 2023
No Comments on Week 5: 3D Compositing Process in Nuke & Garage Homework WIP

This week, we learnt the 3D compositing process to put together plates and CG, to do clean-ups, to regrain, and to do a beauty rebuild with a multipass comp.

The 3D compositing general process looks like the following:

Main plate clean-up and roto work. After finishing the clean-up, it is recommended to render the cleaned plate so we can use this pre-rendered version to do the rest of the comp. This is done so Nuke has less nodes to calculate each time and the preview of the work done goes quicker.
CG compositing. In this part, we can move on with the beauty rebuild, adjusting the AOVs or passes with subtle grade and/or colour correction
- Basic grade match. With a ‘grade’ node, we first do the white balance of the CG that we are going to integrate in the plate, measuring the ‘whitepoint’ (whitest part of the CG) and the ‘blackpoint’ (darkest part of the CG) while holding ‘ctrl+shift+alt’. Subsequently, we go to our background plate and measure ‘gain’ (for the whites) and the ‘lift’ (for the darks) while holding ‘ctrl+shift’. This will balance both plate and CG’s darks and shadows and will integrate them together.
- Multipass comp. In this technique, we need first to ‘unpremult (all)’ our CG so we can start splitting the AOVs or passes. This split is made using ‘shuffle’ node and setting it to the desired pass we want to correct. Before editing the passes, we need to make sure to structure the nodes from the CG plate to a ‘copy’ node with all passes merged together, and double check that the CG plate looks exactly the same from initial point (original plate) to the ‘copy’ node. Sometimes this may look different as some of the passes could have been exported wrong. Once we split our passes we can proceed to ‘grade’ them individually. We ‘merge (plus)’ the light passes and we ‘merge (multiply)’ the shadows. We can also select an ID to create a colour map with ‘Keylight’ node. With this node we can select a specific area of the model that we want to adjust as its features will be separated in different saturated colour mattes. This way we could then re-texture a part of the model using a ‘ST-map’ node connected to the texture source. We can then re-light with ‘position pass’ and ‘normal pass’, followed by a ‘grade’ of the master CG plate. We can finish our beauty rebuild with a ‘copy (alpha-alpha)’ to copy the original alpha to the one created, and we we ‘premult’.

Motion Blur. Motion blur will add more realism and dynamism to the movement of the CG added as in 3D everything looks sharp and in focus so it is not as realistic. We can add motion blur following two methods:
- Method 1: adding a ‘vector blur (rgba)’ node, then link it to ‘camera’, and adjust ‘motion amount’ in the ‘vector blur’ node as desired.
- Method 2: ‘remove (keep)’ node linked to ‘motion blur 3d’ nodes, and adjust this last one’s ‘motion amount’ as desired.

Chroma aberration and defocus. We can add an ‘aberration’ node to match the original camera aberration of the live-footage plate, so we make the scene more credible. Also, with ‘defocus’ node we can add depth to the scene to be able to differentiate between sharp image and out of focus image (depth of field). After adjusting these, we need to add a ‘remove (keep)’ node connected to an ‘ST map’ node to put the original distortion back to the scene.
Regrain. We also could add some grain to the scene with ‘grain’ node. Then with ‘key mix (all)’ node linked to previous changes and ‘grain’, we can mix channels and add a mask to the previous changes made in the comp.
Effect card. We can add effects like smoke with a ‘card’ node. We will need to connect it to ‘shuffle (rgba to rgba with R to alpha)’ node to ‘card’, and ‘grade’ it. Then we ‘copy (alpha to alpha)’ and ‘premult’ to create the alpha of the effect and then we ‘defocus’. This will be projected on a ‘card’ (connected to ‘scene’, ‘scanline render’, and ‘camera’). Finally, we add the ‘ST map’ to unfreeze the frame and ‘multiply’ to show alpha created.
Lightwrap. We use this to add light to the edges, which could be adjusted with ‘diffuse’ and ‘intensity’. Then we will ‘merge (plus)’ as this is light feature.
QC. Using the ‘merge (difference)’ node, we can see and assess the changes made and there is any error. The ‘colour space’ node with the ‘output’ set as ‘HSV’ can be used to check the colours hue (R), saturation (G), and luminance (B) quality.
Final colour correction.
Export. The main preferred format to export our comp would be EXR. Some companies will also want a photo ‘JPEG’, or ‘AppleProRes’, or even ‘Avid DNxHD’, but that depends of the pipeline of each company.

The homework for this week was to start to put together the elements that would form part of our garage comp, and also, include the machine provided by the professor following all the steps we have learnt today.

Following the reference pictures we got with the brief, I started to research for 3D objects I could include such as tools, tyres, a table, etc.

Objects to add to the comp (downloaded from Quixel)

I also decided to re-watch this week’s recording of the lecture to make sure I followed step by step the compositing process. This way, I started to understand the functionality of each node and technique, and to become more confident at the time of creating a whole comp by myself without having to look at references in other comps. The first thing I added was the machine in the back room. I did a beauty rebuilt with the separation of the passes and added a smoke effect with a card 3D projection. I feel like this part went really well as I did not have any issues along the process and the final look is pretty realistic.

Garage comp WIP with machine

After my back machine was fully set, I continued to add the 3D geometry to the comp with its textures. One problem that I had with the objects is the fact that they were really heavy and really jumpy when following the movement of the scene so it was hard to work with.

My work in progress comp looks like the following:

Garage comp WIP with 3D objects

Tags AOVs, Beauty Rebuild, Compositing process, Lightning, Nuke, Passes, Shadows, Texture

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