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/**
* Simple downsample shader. Takes the average of the 4 texels of lower mip.
**/
uniform sampler2DArray source;
uniform vec2 texelSize;
in vec2 uvs;
flat in float layer;
out vec4 FragColor;
void main()
{
/* Reconstructing Target uvs like this avoid missing pixels */
vec2 uvs = gl_FragCoord.xy * 2.0 / vec2(textureSize(source, 0).xy);
#if 0 /* Slower and does not match the main framebuffer downsampling. */
/* Downsample with a 4x4 box filter */
vec4 d = texelSize.xyxy * vec4(-1, -1, +1, +1);
FragColor = texture(source, vec3(uvs + d.xy, layer)).rgba;
FragColor += texture(source, vec3(uvs + d.zy, layer)).rgba;
FragColor += texture(source, vec3(uvs + d.xw, layer)).rgba;
FragColor += texture(source, vec3(uvs + d.zw, layer)).rgba;
FragColor /= 4.0;
#endif
FragColor = texture(source, vec3(uvs, layer));
}
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