Layers & compositing
Every layer stacks bottom-to-top into one final image, with opacity, blend mode and track matte deciding how each mixes with what is beneath it.
Compositing is where a 2D shape, a 3D scene, a video and some text become a single picture.
The stack is evaluated from the bottom layer up, and each layer answers three questions: how strong it is, how it mixes, and what is masking it.
How content stacks
The bottom layer paints first, then each layer above composites over the result so far. The viewport shows the whole stack flattened.
Higher layers paint later, so they cover what is below.
Everything inside a Group paints as one contiguous block, as in After Effects or Figma. Reordering a group moves all its contents at once. That is
isolate, which is on by default. Turn it off and the group becomes an organising scope instead: its contents composite straight against whatever is beneath them, and the group's own opacity and blend mode no longer apply.For real 3D content, whatever is physically nearer the camera draws in front regardless of which layer it is on. Layer order only breaks ties between things at exactly the same depth. For flat 2D and screen overlays, layer order is the whole story.
A stack is therefore two things at once: a paint order for flat content, and true depth for spatial content.
Opacity
Opacity sets how much of a layer shows through. At 100% it fully covers; lower it and the layers beneath read through. A layer at 50% reads as genuinely half-strength rather than washed out. Use it to animate a layer in or out, or to blend a texture into a scene.
The same value doubles as the show/hide switch for a node feeding another node. Wiring a node into something that draws with it sets that node's opacity to 0, so only the result is on screen; drag it back up and both appear. Dropping a layer's opacity to 0 by hand takes it out of the live viewport only, and anything using it as a source, whether a track matte, a bake to raster or a capture, still sees it. See The graph & cooking.
Blend modes
A blend mode changes the maths of how a layer mixes with what is below, so it can brighten, darken, tint or invert instead of covering. 56 ship, grouped by what they do:
Basic: Normal (Over), the default, then Add, Multiply, Screen, Overlay, Subtract, Difference, Darken, Lighten.
Contrast: Soft Light, Hard Light, Vivid Light, Linear Light, Pin Light, Hard Mix, Exclude.
Dodge & burn: Color Dodge, Color Burn, Linear Burn, Divide.
Stencil & cut-out: Under, Atop, Inside, Outside, Xor, and the Stencil / Inside / Outside Luminance variants for masking with one layer's brightness.
Color: Hue, Saturation, Color, Luminosity, which borrow one quality from a layer, such as tint without brightness.
Comparison & effects: Darker and Lighter Color, Chroma and Luminance Difference, Glow, Reflect, Freeze, Heat, Negate, Inverse, Average, Y Film and Z Film, for stylised looks.
Erase: punches a hole in everything below.
Depth & boolean: Depth, ZMerge and MaskedOver resolve by depth rather than order; Union, Intersect, SDF Subtract, SDF Xor and the three Smooth variants combine distance fields as shapes rather than as pixels.
Use Add or Screen so light, fire and glows read as emitting rather than sitting on top. Use Multiply to drop shadows and grime into a scene without hiding the texture underneath.
Every mode mixes in linear light, which keeps highlights and colour transitions clean. An additive glow stays bright and a multiply stays rich rather than going dull at the edges.
Track mattes
A track matte lets one layer control where another is visible, using its shape or brightness as a stencil. Confine a texture to text, reveal a layer through a hand-painted mask, knock content out with an alpha cut-out.
A matte gates the strength of whatever blend mode the layer carries, so a Screen-mode glow can be confined to a masked region in one step.
Wire the matte with the Layer node. Its matte input takes the layer doing the masking, matte_mode picks whether that layer's alpha or its brightness is read, and matte_invert flips the result. Where the masking layer is already a sibling in the stack there is nothing to wire: matte_source picks it by name instead. The same node carries opacity and blend_mode, and those are the layer manager's own fields rather than a second set, so either surface sets them. A Layer node is optional: promoting a branch is a flag on the node itself, and you add a Layer only when you need to wire a matte or a camera in.
The Layer node also carries rasterize. Off, the layer stays live and composites as its own unit. On, its content is baked to a real raster that lives in the scene, which is what makes it readable by downstream nodes and by a feedback loop.
Mattes follow the Nuke-style 'mask gates opacity' model: the matte scales how much the layer contributes, wherever the matte is bright, for whatever blend mode you've chosen.
Stacking inside the graph
The stack above is composition-wide. To combine a handful of things in one place instead, use the Composite node. Sources plug into its slots and a new slot appears as you wire, each with its own blend_N and opacity_N. There is no per-slot switch: a wired slot always composites, so drop its opacity to 0 to mute it.
mode sets what is being combined. Raster bakes every input to a 2D colour image and is the ordinary case. Field keeps inputs in their own space and composes them per channel, which is what engages the distance-field booleans and the smoothness_N that softens them. In Raster mode, composite also decides how the result is presented: Flatten collapses the slots onto one canvas, and In World keeps each one at its own place in 3D and blends them there.
Promoting a node into its own layer
Content normally flows down a single chain and lands in one place. Promote a branch to make it an independent layer with its own opacity, blend mode and matte. The branch renders separately and hands its finished image to the stack as a distinct layer, which is how a 3D scene, a 2D Expression result and a video can live in one project and still mix on their own terms.
Promote when two parts of the graph need different compositing treatment. If a glow pass needs Add while the base stays Over, promote the glow so it carries its own blend mode into the stack.
A promoted flat layer is a compositing unit, not a scene object, so it has no place in the 3D world for anything that queries the scene: a Ray passes through it, and physics and ambient lookups do not find it. Give it a real world placement with a Projection node in Camera mode and it becomes a card that lives in the scene, at which point those queries reach it like any other geometry.