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