Gradients for polygons in OpenGL

what 开发者_StackOverflow中文版is the best way to create a gradient for a 2D polygon in OpenGL, (Linear, and Radial)?

Thanks

How can you generate textures for radial gradients on the fly?

Linear is very easy - you just set different colors to different points like

red ---- red
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blue ---- blue

for radial texture might be better option

to generate it on fly create empty texture then fill it with function sqrt((MAXX - x)^2 + (MAXY - y)^2), then add color to it.