3D Graphics Programming with QuickDraw 3D 1.5.4

Boundary-Handling Methods

You use a boundary-handling method specifier to indicate how you want a shader to handle uv values that are outside the valid range (namely, 0 to 1). For example, you pass one of these constants to the Q3Shader_SetUBoundary function to indicate how to handle values in the u parametric direction that lie outside the valid range.

For a fuller description of boundary-handling methods, see "Handling uv Values Outside the Valid Range" .



 
typedef enum TQ3ShaderUVBoundary {

    kQ3ShaderUVBoundaryWrap,

    kQ3ShaderUVBoundaryClamp

} TQ3ShaderUVBoundary;

Constant descriptions

kQ3ShaderUVBoundaryWrap: Values outside the valid range are to be wrapped. To wrap a shader effect is to replicate the entire effect across the mapped area. For example, for a texture shader, wrapping causes the entire image to be replicated across the surface onto which the texture is mapped.
kQ3ShaderUVBoundaryClamp: Values outside the valid range are to be clamped. To clamp a shader effect is to replicate the boundaries of the effect across the portion of the mapped area that lies outside the valid range. For example, for a texture shader, clamping causes boundaries of the image to be smeared across the portion of the surface onto which the texture is mapped that lies outside the valid range.