pandory500/SDL-mirror
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Updated blend semantics so blending uses the following formula:

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dstRGB = (srcRGB * srcA) + (dstRGB * (1-srcA))
    dstA = srcA + (dstA * (1-srcA))
This allows proper compositing semantics without requiring premultiplied alpha.

Needs full unit test coverage and bug fixes!
This commit is contained in:
Sam Lantinga 2013-07-23 08:06:49 -07:00
parent a99edf3519
commit 32188834b5
17 changed files with 362 additions and 1001 deletions
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6
src/render/opengl/SDL_render_gl.c
View file

@ -924,17 +924,17 @@ GL_SetBlendMode(GL_RenderData * data, int blendMode)
case SDL_BLENDMODE_BLEND:
data->glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
data->glEnable(GL_BLEND);
data->glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
data->glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
break;
case SDL_BLENDMODE_ADD:
data->glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
data->glEnable(GL_BLEND);
data->glBlendFunc(GL_SRC_ALPHA, GL_ONE);
data->glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE, GL_ZERO, GL_ONE);
break;
case SDL_BLENDMODE_MOD:
data->glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
data->glEnable(GL_BLEND);
data->glBlendFunc(GL_ZERO, GL_SRC_COLOR);
data->glBlendFuncSeparate(GL_ZERO, GL_SRC_COLOR, GL_ZERO, GL_ONE);
break;
}
data->current.blendMode = blendMode;