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King of Men

OpenGL Gradient blending

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I'm trying to draw hexes for a simple 2D game. I'd like to have different textures for different terrain in the hexes, and then blend the textures at the edges so as to create a smooth transition. It seems to me that this could be done by telling OpenGL to blend on a gradient, so that one end of a quad was fully one texture and the other end was fully the other, and a linear mix in between; but my Google-fu is not strong enough to tell me how this can be done. Can anyone point me to what I should look for? This seems like it ought to be a standard technique, so maybe I'm just missing the right keywords.

Alternatively, am I barking up the wrong tree and should use a different technique?

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Do you understand shading language for OpenGL? This should be fairly simple to implement if you want to write a multitexture shader for it.

Alternatively, you could just draw the hex twice (once with each texture) and use additive blending to achieve the effect.

E.g. for a rectangle you'd use the following alpha values for each vertex:


Pass 1:
1 ---------- 0
| |
| |
1 ---------- 0

Pass 2:
0 ---------- 1
| |
| |
0 ---------- 1


Personally I'd go for the shader (its a bit faster), but not everyone is willing to learn it.

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