38 lines
683 B
GLSL
38 lines
683 B
GLSL
/* Shader for approximating the way RMXP does bitmap
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* blending via DirectDraw */
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uniform sampler2D source;
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uniform sampler2D destination;
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uniform vec4 subRect;
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uniform float opacity;
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varying vec2 v_texCoord;
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void main()
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{
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vec2 coor = v_texCoord;
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vec2 dstCoor = (coor - subRect.xy) * subRect.zw;
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vec4 srcFrag = texture2D(source, coor);
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vec4 dstFrag = texture2D(destination, dstCoor);
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vec4 resFrag;
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float ab = opacity;
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float as = srcFrag.a;
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float ad = dstFrag.a;
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float at = ab*as;
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resFrag.a = at + ad - ad*at;
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// Sigh...
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if (ad == 0.0)
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resFrag.rgb = srcFrag.rgb;
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else
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resFrag.rgb = as*srcFrag.rgb + (1.0-at) * ad * dstFrag.rgb;
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gl_FragColor = resFrag;
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}
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