56 lines
2.0 KiB
Plaintext
56 lines
2.0 KiB
Plaintext
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#version 310 es
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layout(local_size_x = 8, local_size_y = 8) in;
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layout(binding = 0) uniform sampler2D uHeight;
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layout(binding = 1) uniform sampler2D uDisplacement;
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layout(rgba16f, binding = 2) uniform writeonly mediump image2D iHeightDisplacement;
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layout(rgba16f, binding = 3) uniform writeonly mediump image2D iGradJacobian;
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layout(binding = 4) uniform UBO
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{
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vec4 uInvSize;
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vec4 uScale;
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};
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mediump float jacobian(mediump vec2 dDdx, mediump vec2 dDdy)
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{
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return (1.0 + dDdx.x) * (1.0 + dDdy.y) - dDdx.y * dDdy.x;
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}
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#define LAMBDA 1.2
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void main()
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{
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vec4 uv = (vec2(gl_GlobalInvocationID.xy) * uInvSize.xy).xyxy + 0.5 * uInvSize;
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float h = textureLod(uHeight, uv.xy, 0.0).x;
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// Compute the heightmap gradient by simple differentiation.
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float x0 = textureLodOffset(uHeight, uv.xy, 0.0, ivec2(-1, 0)).x;
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float x1 = textureLodOffset(uHeight, uv.xy, 0.0, ivec2(+1, 0)).x;
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float y0 = textureLodOffset(uHeight, uv.xy, 0.0, ivec2(0, -1)).x;
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float y1 = textureLodOffset(uHeight, uv.xy, 0.0, ivec2(0, +1)).x;
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vec2 grad = uScale.xy * 0.5 * vec2(x1 - x0, y1 - y0);
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// Displacement map must be sampled with a different offset since it's a smaller texture.
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vec2 displacement = LAMBDA * textureLod(uDisplacement, uv.zw, 0.0).xy;
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// Compute jacobian.
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vec2 dDdx = 0.5 * LAMBDA * (
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textureLodOffset(uDisplacement, uv.zw, 0.0, ivec2(+1, 0)).xy -
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textureLodOffset(uDisplacement, uv.zw, 0.0, ivec2(-1, 0)).xy);
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vec2 dDdy = 0.5 * LAMBDA * (
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textureLodOffset(uDisplacement, uv.zw, 0.0, ivec2(0, +1)).xy -
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textureLodOffset(uDisplacement, uv.zw, 0.0, ivec2(0, -1)).xy);
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float j = jacobian(dDdx * uScale.z, dDdy * uScale.z);
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displacement = vec2(0.0);
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// Read by vertex shader/tess shader.
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imageStore(iHeightDisplacement, ivec2(gl_GlobalInvocationID.xy), vec4(h, displacement, 0.0));
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// Read by fragment shader.
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imageStore(iGradJacobian, ivec2(gl_GlobalInvocationID.xy), vec4(grad, j, 0.0));
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}
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