Yusuf's Thoughts

SOP - Surface Operators

2 min read

SOP - Surface Operators (3D)

SOPs are used for 3D geometry and point data.

Key SOPs

  • Sphere/Box/Torus: Basic primitives.
  • Grid: A flat plane of points.
  • Noise: Deform geometry using 3D noise patterns.
  • Copy: Repeat geometry at specific points.
  • Attribute Create: Calculate normals or tangents.
  • Group: Organize subsets of points or primitives.

Anatomy of a SOP

Understanding how TouchDesigner structures 3D geometry is vital:

  • Points: The lowest level. Just XYZ coordinates in space.
  • Vertices: A reference to a Point, used to build higher-order shapes. (Multiple vertices can share a single point).
  • Primitives: The faces, lines, or polygons constructed by connecting vertices.

Example: A Box SOP has 8 Points (corners). But it has 6 Primitives (faces). Because each face needs 4 corners, the Box actually consists of 24 Vertices mapped back to those 8 logical Points.

How to Use SOPs

SOPs are the traditional way of modeling and manipulating 3D data in TouchDesigner, executed on the CPU.

  1. Adding a SOP: Open the OP Create Dialog (Tab) and select the SOP family (blue color).
  2. Creating Geometry: Start with generator SOPs like Box, Sphere, or Torus.
  3. Modifying Geometry: Pass the generator output into modifier SOPs like Transform to move it, Noise to deform point positions, or Facet to compute normals.
  4. Connecting: Drag from the output on the right to an input on the left to pass geometry data.
  5. Viewing Data: Middle-click any SOP to see how many points, vertices, and primitives it contains. Right-click the node and select “View” to open a separate 3D viewer.
  6. Rendering Process: SOPs run on the CPU. To see them rendered on the GPU with textures and lighting:
    • Connect your final SOP to a Null SOP.
    • Right-click the Null SOP’s output and select a Geometry COMP (under the COMP tab).
    • This places your SOP data inside an object that can be rendered using a Render TOP, along with a Camera COMP and a Light COMP.

(y-) Next Chapter: TOPs

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