Table of Contents Glide Programming Guide

Other Color Combine Options

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1Other Color Combine Options

The routine grAlphaControlsITRGBLighting() can be used to specify that if the high order bit of a_texture is 1, then the constant color set by grConstantColorValue() is used instead of the iterated RGB values. This is useful if a portion of a texture is to appear to be illuminated from behind the surface, instead of by an external light source.
void grAlphaControlsITRGBLighting( FxBool enable )

When enabled, the normal color combine controls for local color (c_local) are overridden, and the most significant bit of texture alpha (a_texture) selects between iterated vertex RGB and the constant color set by grConstantColorValue(). By default, this alpha controlled lighting mode is disabled. Table Color and Lighting.4 shows how c_local is determined.

Table Color and Lighting.4 Overriding the local color when the high order bit of a_texture is set.

You can get hybrid effect between smooth and flat shading by using grAlphaControlsITRGBLighting() to enable a technique whereby the high order bit of a_texture is used to switch c_local between iterated RGB and the constant color. The state table below shows how the c_local value is determined.

When enable* is*	and the high order bit of a_texture is	the local color c_local will be
FXTRUE	0	iterated RGB
FXTRUE	1

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