V-Ray for Rhino Manual - Rum

Projection types and adjustment
The different types of projection are Surface, Planar, Box, Spherical, Cylindrical and Capped cylindrical.
Rhino sets the default to Surface if there is no other projection assigned to the object and render the
object according to its UV directions.
When change to a different projection, the default size of mapping widget is set to the perimeter of
the object.
Show Mapping is to display the mapping widget in the scene. Within the working window, the mapping
widget can be moved, rotated and scaled.
An object can have multiple projections at the same time, each
within a different channel. Use Add to create a new channel. Under
Material Editor>Texture Editor, you can select the channel for each
texture to work with. Use Edit to number the channel. Use Delete to
delete current channel. Other adjusting options include Position,
Rotation, Size, UVW offset, UVW Rotation and UVW repeat.
Type of projection, size and position of Mapping Widget, project
direction will all affect the Bitmap on the object. Of course, those will also affect the final render
result.
Below are examples using teapot to show different UI setting. Use correspondent UI for different
object. Spend some times to find exact what you want to get the ideal render result.
Box
Spherical
Cylindrical
Click on F10 to show the control point for
the Mapping Widget. Move those points to
adjust the size of Mapping Widget
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V-Ray for Rhino