Mesh > Mesh Cleanup > Mesh Reduce

Reduces the number of triangles in a mesh while attempting to preserve its shape.

Sometimes, a mesh contains more triangles than are necessary to represent its shape accurately. The Mesh Reduce tool lets you reduce the number of triangles in a mesh (while attempting to preserve its shape) according to two different methods:

Based on chordal deviation, given a maximum deviation value.
Down to a given percentage (fraction) of the original number.

Mesh Reduce Options

Num Triangles/Num Vertices/Deviation: Non-editable fields displaying the number of triangles, number of vertices and deviation from the original mesh (in linear units) after each reduction step.
Mode: CHORDAL DEVIATION – The number of triangles is reduced so that chordal deviation from the original mesh does not exceed a given maximum deviation value.

FRACTION – The number of triangles is reduced down to a given percentage (fraction) of the original number.
Max Deviation: Specifies the maximum chordal deviation distance allowed during the retessellation.

This option is only available if Mode is CHORDAL DEVIATION.
Reduction %: Specifies the percentage of the original number of triangles to keep in the mesh.

This option is only available if Mode is FRACTION.
Show Deviation Map: If this option is checked, a color deviation map displays the deviation between the original mesh (prior to entering the tool) and the reduced mesh. A deviation scale (ramp) also appears. This shows you what areas of the mesh have been affected, and by how much.

Deviation Map Settings

These options only appear if Show Deviation Map is checked on.

Auto Ramp: If this option is checked (default), the color scale updates automatically based on a range between zero and the maximum deviation from the last operation.

Note
If Auto Ramp is on, and the maximum deviation is less than the Acceptable Distance, the Acceptable Distance is set to 10% of the maximum deviation, to avoid a completely green color map.
Ramp Distance: Maximum distance between original and modified mesh shown on the color ramp. Areas on the mesh where the deviation is larger than this value are displayed in a solid color (red or purple). The default is 10.0 mm.
Acceptable Distance: Upper limit for the acceptable deviation between original and modified mesh. Regions of the mesh where the deviation is smaller than this value are colored in green. The default is 1.0 mm.

Where the value of the deviation is between the Acceptable Distance and the Ramp Distance, the mesh displays intermediate colors as shown on the ramp.

Note
The Ramp Distance must be kept larger than the Acceptable Distance.
Absolute Value Ramp: Turn on this option if you are not concerned with the direction of the deviation and simply want to view absolute deviation values.
Use Bands: Turn on this option if you want the ramp to display solid bands of color instead of slowly varying colors.