2.8Simulation Quality

Five controls on the Solver panel set the quality of the solve. The first two are the ones to understand.

• Substeps divide each frame into shorter slices of time. Everything, including collision, is evaluated again in every slice. Substeps fix a garment that moves too fast for the solver to keep up with: fast body motion, whipping hems, anything that travels a long way in one frame.
• Iterations solve the constraints again inside the slice that is already running. Time does not advance and collision is not evaluated again. Iterations tighten a solve that is nearly right.

Raise Substeps first: it is the more effective of the two for almost every problem an artist meets. The two multiply: the solver does substeps × iterations constraint passes per frame, and that product is the first number to look at when a scene is slow.

• Contact passes is the collision quality. Raise it together with Iterations and Stretch quality: raising those two while Contact passes stays at 1 costs more time and can give more penetration, not less.
• Stretch quality adds passes for the stretch constraints only. Raise it when a material's stretch status line says the stretch is still converging.
• Smoothing iterations evens out the fine zigzag a dense mesh can show, without adding or removing motion.

Quality steps

The Quality tool on the TenPix toolbar applies these steps to one Solver or many. Normal is the default of a new Solver.

Rule of thumb from the same tool: Iterations or Stretch quality of 4 or more want at least 4 contact passes; 8 or more want at least 7.