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 (we call it dicing).

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 or define a dicing camera.

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.
  • Displacement impacts time to first pixel but doesn't slow shading.
• Bump or normal maps will add small scale details
  • Bump mapping add small cost during shading.

If you have modeled a highly detailed object in ZBrush, you should consider retopologizing and extracting a displacement map.

Memory usage