diff options
Diffstat (limited to 'source/blender/gpu/shaders/compositor/compositor_blur.glsl')
| -rw-r--r-- | source/blender/gpu/shaders/compositor/compositor_blur.glsl | 21 |
1 files changed, 16 insertions, 5 deletions
diff --git a/source/blender/gpu/shaders/compositor/compositor_blur.glsl b/source/blender/gpu/shaders/compositor/compositor_blur.glsl index 4f981c84f59..c7ac620f99b 100644 --- a/source/blender/gpu/shaders/compositor/compositor_blur.glsl +++ b/source/blender/gpu/shaders/compositor/compositor_blur.glsl @@ -18,13 +18,24 @@ vec4 load_input(ivec2 texel) } /* Given the texel in the range [-radius, radius] in both axis, load the appropriate weight from - * the weights texture, where the texel (0, 0) is considered the center of weights texture. */ + * the weights texture, where the given texel (0, 0) corresponds the center of weights texture. + * Note that we load the weights texture inverted along both directions to maintain the shape of + * the weights if it was not symmetrical. To understand why inversion makes sense, consider a 1D + * weights texture whose right half is all ones and whose left half is all zeros. Further, consider + * that we are blurring a single white pixel on a black background. When computing the value of a + * pixel that is to the right of the white pixel, the white pixel will be in the left region of the + * search window, and consequently, without inversion, a zero will be sampled from the left side of + * the weights texture and result will be zero. However, what we expect is that pixels to the right + * of the white pixel will be white, that is, they should sample a weight of 1 from the right side + * of the weights texture, hence the need for inversion. */ vec4 load_weight(ivec2 texel) { - /* Add the radius to transform the texel into the range [0, radius * 2], then divide by the upper - * bound plus one to transform the texel into the normalized range [0, 1] needed to sample the - * weights sampler. Finally, also add 0.5 to sample at the center of the pixels. */ - return texture(weights_tx, (texel + vec2(radius + 0.5)) / (radius * 2 + 1)); + /* Add the radius to transform the texel into the range [0, radius * 2], with an additional 0.5 + * to sample at the center of the pixels, then divide by the upper bound plus one to transform + * the texel into the normalized range [0, 1] needed to sample the weights sampler. Finally, + * invert the textures coordinates by subtracting from 1 to maintain the shape of the weights as + * mentioned in the function description. */ + return texture(weights_tx, 1.0 - ((texel + vec2(radius + 0.5)) / (radius * 2 + 1))); } void main() |