Yusuf's Thoughts

Render TOP

3 min read

Render TOP

The Render TOP is what converts your 3D scene — geometry, lights, cameras, and materials — into a 2D image you can display, process, or output. It is the bridge between the 3D (SOP/COMP) world and the 2D (TOP) world.

Key Parameters

Render Page

ParameterDescription
CameraPath to the Camera COMP that defines the viewpoint
GeometryComma-separated list of Geometry COMPs to render. Leave blank to auto-discover all visible Geo COMPs in the same level
LightsPath(s) to Light COMPs. Leave blank for auto-discovery
Background ColorRGBA colour of the area behind all geometry
Clear OptionsWhat to clear before each frame: colour, depth, both, or neither

Common Page

ParameterDescription
ResolutionOutput texture size (e.g. 1920×1080)
Pixel FormatBit depth: 8-bit fixed for standard use; 32-bit float for HDR and compositing

Minimal 3D Scene Setup

The fastest way to get a rendered scene is:

Box SOP → Geo COMP
Camera COMP
Light COMP
Render TOP  ← set Camera to the Camera COMP
  → Null TOP (OUT_RENDER)
  1. Create a Geo COMP and connect your geometry SOP into its first input.
  2. Add a Camera COMP and a Light COMP at the same network level as the Geo COMP.
  3. Add a Render TOP. It will auto-discover the Camera and Lights if they are at the same level.
  4. Hit play — you’ll see the geometry rendered.

Multiple Geometry Objects

To render several objects, either:

  • List them explicitly in the Geometry parameter: /project1/geo1, /project1/geo2
  • Or put all geometry inside a Container COMP and reference that level — the Render TOP discovers everything inside it.

Post-Processing the Image

Because the Render TOP outputs a standard TOP, you can chain any TOP after it:

Render TOP → Level TOP (adjust brightness/contrast)
           → Blur TOP
           → Composite TOP (overlay UI elements)
           → Out TOP

Multiple Render Passes

For effects that require separation (e.g. rendering geometry and particles separately to composite them):

  1. Use two Render TOPs, one per layer.
  2. Control which geometry each renders by setting the Geometry parameter explicitly.
  3. Use a Composite TOP or Over TOP to combine them.

Pixel Format Tips

  • 8-bit fixed (RGBA) — standard, fast, enough for most work
  • 16-bit float (RGBA) — better for compositing with transparency
  • 32-bit float (RGBA) — full HDR; needed for GLSL shaders that output values outside 0–1

Common Gotchas

  • Black output → check that the Camera COMP path is correct and that geometry is inside the camera’s frustum.
  • Geometry not appearing → make sure the Geo COMP’s visible flag (eye icon) is on, and its material is assigned.
  • Render is slow → reduce resolution, reduce polygon count upstream in SOPs, or use instancing instead of duplicating geometry.
  • Alpha is not transparent → set the Background Color alpha to 0 and use a pixel format with alpha (RGBA).
  • The Render TOP does not need to be connected to the Camera COMP or Geo COMP with wires — it references them by name/path.

(y-) Next Chapter: Rendering & Output

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