Contents
Pick the right tool for the job
In general, subdivision surfaces have many advantages but sometimes you actually need a polygon mesh.
Subdivision surfaces
- Pros
- Perfectly smooth at any resolution.
- Can have sharp or semi-sharp features with creases and corners.
- Can be very lightweight in memory.
- Less displacement cracks (watertight)
- Cons
- Different modeling techniques/skills
- Need to tag sharp edges and vertices
- Some topological constraints (no holes or non-manifold geometry)
Polygon meshes
- Pros
- Great for heavy geometry like 3D scanned mesh
- Best for geometry that will be fractured / simmed.
- Good for models with only sharp edges that don't need displacement
- No microploygon generation if not displaced.
- Cons
- Heavy models use a lot of memory, however small they may be in the image.
- Shadow terminator may be visible on low resolution smoothed objects
- Displacement cracks may be visible
Subdivision modeling
- Always model the simplest control cage possible.
- Always view your model with smoothing or render it using PxrVisualizer.
- You can even model in a live PxrVisualizer render !
- Use creases to make sharp or semi-sharp edges without adding extra edge loops.
- Corners work like creases for vertices.
Tesselation
If you are coming from another renderer where you have to set subdivision levels, forget about it: tesselation of surfaces is automatic in RenderMan.
The main control is the micropolygon length.
- By default, it is expressed in pixels and a micropolygonlength of 1 (the default) means that every micropolygon will be approximately 1 pixel wide.
- If you don't want the tesselation to change dynamically, you can set it in object or world space.
Model detailing
Often, it is better to rely on displacement and bump mapping to add details.
- Displacement allows you to add larger geometric features that impact your object's outline and shadowing.
- Bump or normal maps will add small scale details, at a small cost during shading.