varying vec2 v_textureCoordinates;
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uniform float originalSize;
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uniform sampler2D texture0;
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uniform sampler2D texture1;
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uniform sampler2D texture2;
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uniform sampler2D texture3;
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uniform sampler2D texture4;
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uniform sampler2D texture5;
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const float yMipLevel1 = 1.0 - (1.0 / pow(2.0, 1.0));
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const float yMipLevel2 = 1.0 - (1.0 / pow(2.0, 2.0));
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const float yMipLevel3 = 1.0 - (1.0 / pow(2.0, 3.0));
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const float yMipLevel4 = 1.0 - (1.0 / pow(2.0, 4.0));
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void main()
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{
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vec2 uv = v_textureCoordinates;
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vec2 textureSize = vec2(originalSize * 1.5 + 2.0, originalSize);
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vec2 pixel = 1.0 / textureSize;
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float mipLevel = 0.0;
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if (uv.x - pixel.x > (textureSize.y / textureSize.x))
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{
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mipLevel = 1.0;
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if (uv.y - pixel.y > yMipLevel1)
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{
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mipLevel = 2.0;
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if (uv.y - pixel.y * 3.0 > yMipLevel2)
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{
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mipLevel = 3.0;
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if (uv.y - pixel.y * 5.0 > yMipLevel3)
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{
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mipLevel = 4.0;
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if (uv.y - pixel.y * 7.0 > yMipLevel4)
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{
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mipLevel = 5.0;
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}
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}
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}
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}
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}
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if (mipLevel > 0.0)
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{
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float scale = pow(2.0, mipLevel);
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uv.y -= (pixel.y * (mipLevel - 1.0) * 2.0);
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uv.x *= ((textureSize.x - 2.0) / textureSize.y);
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uv.x -= 1.0 + pixel.x;
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uv.y -= (1.0 - (1.0 / pow(2.0, mipLevel - 1.0)));
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uv *= scale;
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}
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else
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{
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uv.x *= (textureSize.x / textureSize.y);
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}
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if(mipLevel == 0.0)
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{
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gl_FragColor = texture2D(texture0, uv);
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}
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else if(mipLevel == 1.0)
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{
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gl_FragColor = texture2D(texture1, uv);
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}
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else if(mipLevel == 2.0)
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{
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gl_FragColor = texture2D(texture2, uv);
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}
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else if(mipLevel == 3.0)
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{
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gl_FragColor = texture2D(texture3, uv);
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}
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else if(mipLevel == 4.0)
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{
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gl_FragColor = texture2D(texture4, uv);
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}
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else if(mipLevel == 5.0)
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{
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gl_FragColor = texture2D(texture5, uv);
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}
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else
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{
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gl_FragColor = vec4(0.0);
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}
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}
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