glBlendColor example c c++ objc java

Name

glBlendColor — set the blend color

C Specification

void glBlendColor(	GLclampf	red,
	GLclampf	green,
	GLclampf	blue,
	GLclampf	alpha);

Parameters

red, green, blue, alpha

specify the components of GL_BLEND_COLOR

Description of glBlendColor

The GL_BLEND_COLOR may be used to calculate the source and destination blending factors. The color components are clamped to the range 0 1 before being stored. See glBlendFunc for a complete description of the blending operations. Initially the GL_BLEND_COLOR is set to (0, 0, 0, 0).

Notes

glBlendColor is part of the ARB_imaging subset. glBlendColor is present only if ARB_imaging is returned when glGetString is called with GL_EXTENSIONS as its argument.

Errors

GL_INVALID_OPERATION is generated if glBlendColor is executed between the execution of glBegin and the corresponding execution of glEnd.

Associated Gets

glGet with an argument of GL_BLEND_COLOR

See Also

glBlendEquation, glBlendFunc, glGetString

Copyright

Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.

Example

 glBlendColor(1,0,0,1);

 glBlendFunc(GL_CONSTANT_COLOR, GL_ZERO);

 glEnable(GL_BLEND);

 will generate a red tint to everything you render (that would otherwise
 be unblended). Also,


 glBlendColor(0,0,0,0.5);

 glBlendFunc(GL_CONSTANT_ALPHA, GL_ONE_MINUS_CONSTANT_ALPHA);

 glEnable(GL_BLEND);


 will render with 50% opacity.