Where to Use Which Approximation
Although there is no hard and fast rule on which approximation to use for a given object, here are a few rules of thumb you can follow to optimize a rendered scene’s quality:
• Parametric approximation—Used if you have a largely flat-based surface as well as some displacement.
• Length approximation—Especially useful when combined with view dependency because it lets you control the approximate number of triangles per pixel.
• Distance approximation—Used on objects that have a gentle curve, since they don’t usually have two neighboring triangles with a large normal distance.
• Angle approximation—Used on objects that have localized areas with high curvature, such as a cube with rounded edges.
• Fine approximation—Used on objects that require very detailed approximation. This type of approximation is well-suited to displacement mapping.
To set the surface approximation for an object
1. Select an object in the viewport whose surface you want to edit.
2. If the object does not yet have a local Geometry Approximation property assigned to it, assign one now by choosing Get > Property > Geometry Approximation from the Render toolbar.
3. Click the Selection button on the Select panel to display the selected object’s nodes in a pop–up explorer.
4. Click the Geometry Approximation icon to open its property editor.
5. Click the Surface tab and select a type of surface approximation: Parametric, Length/Distance/Angle, or Fine (see the next sections for more information).
Depending on the surface approximation you choose, Softimage tries to create the perfect curve between two points.
Autodesk Softimage v.7.5