1 The idea
No task. Start from a ready-made shot: plate, robot and sparks. Add nodes from the bar under Properties, delete with the Delete key, and rewire as you like.
Try the deep-dive experiments one at a time, such as switching plus to over or adding an extra Premult under the robot, and probe values before and after.
2 Hands-on in the mini compositor
3 Deep dive
Reading a graph like a compositor
The main pipe (the B pipe) runs straight down from the plate. Each element joins from the side through A. Finish an element on its own branch before it reaches the Merge.
- 1Plate
- 2Over robot
- 3Plus sparks
- 4Grain (last)
- 5Write
A straight main pipe always reads faster than one that wanders
Experiments worth trying
Try one at a time and probe values before and after. Each one ties back to an earlier lesson.
| Try | Watch | You learn |
|---|---|---|
| Switch the sparks Merge from plus to over | Almost nothing changes | Alpha 0 makes over = plus |
| Switch it to screen | The spark cores | Above 1, screen returns max(A, B), so the plate’s light is lost (it does not cap at 1) |
| Grade lift on the sparks branch | The whole frame | Lift raises every dark pixel, and plus adds it to the plate |
| A Premult under the robot Read | Arm edges | Double premult = dark rim |
| Blur on the robot branch vs after the Merge | The plate | Fix elements before combining |
Debugging in three moves
One: view node by node, top to bottom. Two: disable the suspect node (D) and compare. Three: probe one pixel and follow its number all the way down.
Always change one thing at a time. Change two at once and you will not know which one worked.
- 1View each node
- 2Disable (D)
- 3Follow a pixel
Order in a full shot
In a real shot the rough order is: prepare the plate → fix each element on its branch → combine with Merges → atmosphere and defocus → grain once, at the very end.
Add grain early and then blur or grade over it, and the grain gets smeared. Add it in two places and it ends up heavier than the plate.
4 In real work
In Nuke
- Read plate is the main pipe, running straight down
- Read robot → (Grade if needed) → Merge over (A)
- Read sparks → Grade multiply → Merge plus (A)
- Blur / Transform for an element stay on its branch, before the Merge
- One Grain node just before the Write
Common mistakes → the fix
- ✗ Blurring after the Merge to soften one element✓ The whole picture blurs. Move it onto the element’s branch.
- ✗ Fixing one element by grading the main pipe✓ The plate changes too. Grade on the element’s branch.
- ✗ Changing several things at once while debugging✓ Change one thing, then compare.
- ✗ Leaving disabled test nodes in the delivered script✓ Delete them or label them clearly so the next artist is not confused.
Before you send the shot
- The main pipe reads top to bottom at a glance
- All element fixes live on their own branches
- Light goes in with plus, solid things with over
- Grain is added once, at the end
- No leftover test nodes
5 Check yourself
You want the sparks softer without blurring the robot. Where does the Blur go?
🔒 Answer the question above and this card opens
1. You switch the sparks Merge from plus to over and almost nothing changes. Why?
2. You put a Grade lift of 0.05 on the sparks branch, then Merge plus. What happens?
Where the numbers come from: Merge, Grade, Premult and Unpremult here match Nuke 17.0v2 in all 109 test cases (numbers sampled from real Nuke). Blur and Transform are simplified: close, not identical to Nuke. All images are Blender renders of our own scene: a code-built layout with hills made as Gaea 2.3 terrains (Community edition, built headless), a Poly Haven CC0 HDRI sky, Poly Haven (CC0) rocks and dry grass, Quixel sand and cliff textures, and a robot on a Mixamo rig (Quixel and Mixamo are used in the renders only; no source files ship).