Mirror smin_grad and cellular in CultMath.hlsl
Adds cultmath_smin_grad, the CultCellular struct, and cultmath_cellular to both tracked copies of CultMath.hlsl (packages/cultmath/shaders and the Unity package), placed after cultmath_pcg4d so cultmath_cellular can call cultmath_pcg3d and cultmath_distance, both of which HLSL requires to be declared earlier in the file. Both copies stay byte-identical. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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2 changed files with 136 additions and 0 deletions
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@ -313,6 +313,74 @@ int4 cultmath_pcg4d(int4 value)
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int4 cultmath_pcg4d(float4 value) { return cultmath_pcg4d(int4((int)asuint(value.x), (int)asuint(value.y), (int)asuint(value.z), (int)asuint(value.w))); }
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// Inigo Quilez, "smooth minimum": cubic-polynomial smin carried to value-and-gradient form. See
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// math.smin_grad's comment (math.cs) for why the gradient blend is exact, not an approximation.
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float4 cultmath_smin_grad(float4 a, float4 b, float k)
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{
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float h = saturate(0.5 + 0.5 * (b.w - a.w) / k);
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float value = lerp(b.w, a.w, h) - k * h * (1.0 - h);
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float3 gradient = lerp(b.xyz, a.xyz, h);
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return float4(gradient, value);
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}
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// Invariant 8's one struct return shape (design.md, "HLSL Target: Source Transformations"):
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// compared field by field and bit for bit against CultMath.CultCellular, same field order.
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struct CultCellular
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{
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float4 nearest;
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float4 edge;
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float id;
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};
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// Worley, "A Cellular Texture Basis Function" (SIGGRAPH 1996). See math.cellular's comment
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// (math.cs) for the hashing, gradient and degenerate-point conventions this mirrors.
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CultCellular cultmath_cellular(float3 p)
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{
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float3 cell = floor(p);
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float f1 = 1.0e30;
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float f2 = 1.0e30;
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float3 c1 = float3(0.0, 0.0, 0.0);
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float3 c2 = float3(0.0, 0.0, 0.0);
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int hash1 = 0;
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for (int dz = -1; dz <= 1; dz++)
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{
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for (int dy = -1; dy <= 1; dy++)
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{
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for (int dx = -1; dx <= 1; dx++)
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{
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float3 neighbor = cell + float3(dx, dy, dz);
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int3 hash = cultmath_pcg3d(neighbor);
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float3 jitter = float3(
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(uint)hash.x * (1.0 / 4294967296.0),
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(uint)hash.y * (1.0 / 4294967296.0),
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(uint)hash.z * (1.0 / 4294967296.0));
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float3 feature = neighbor + jitter;
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float d = cultmath_distance(p, feature);
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if (d < f1)
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{
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f2 = f1; c2 = c1;
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f1 = d; c1 = feature; hash1 = hash.x;
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}
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else if (d < f2)
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{
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f2 = d; c2 = feature;
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}
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}
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}
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}
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float3 grad1 = f1 > 0.0 ? (p - c1) / f1 : float3(0.0, 0.0, 0.0);
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float3 grad2 = f2 > 0.0 ? (p - c2) / f2 : float3(0.0, 0.0, 0.0);
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CultCellular result;
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result.nearest = float4(grad1, f1);
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result.edge = float4(grad2 - grad1, f2 - f1);
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result.id = (uint)hash1 * (1.0 / 4294967296.0);
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return result;
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}
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float cultmath_value_noise(float2 position)
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{
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float2 cell = floor(position);
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@ -313,6 +313,74 @@ int4 cultmath_pcg4d(int4 value)
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int4 cultmath_pcg4d(float4 value) { return cultmath_pcg4d(int4((int)asuint(value.x), (int)asuint(value.y), (int)asuint(value.z), (int)asuint(value.w))); }
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// Inigo Quilez, "smooth minimum": cubic-polynomial smin carried to value-and-gradient form. See
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// math.smin_grad's comment (math.cs) for why the gradient blend is exact, not an approximation.
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float4 cultmath_smin_grad(float4 a, float4 b, float k)
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{
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float h = saturate(0.5 + 0.5 * (b.w - a.w) / k);
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float value = lerp(b.w, a.w, h) - k * h * (1.0 - h);
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float3 gradient = lerp(b.xyz, a.xyz, h);
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return float4(gradient, value);
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}
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// Invariant 8's one struct return shape (design.md, "HLSL Target: Source Transformations"):
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// compared field by field and bit for bit against CultMath.CultCellular, same field order.
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struct CultCellular
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{
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float4 nearest;
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float4 edge;
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float id;
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};
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// Worley, "A Cellular Texture Basis Function" (SIGGRAPH 1996). See math.cellular's comment
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// (math.cs) for the hashing, gradient and degenerate-point conventions this mirrors.
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CultCellular cultmath_cellular(float3 p)
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{
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float3 cell = floor(p);
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float f1 = 1.0e30;
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float f2 = 1.0e30;
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float3 c1 = float3(0.0, 0.0, 0.0);
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float3 c2 = float3(0.0, 0.0, 0.0);
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int hash1 = 0;
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for (int dz = -1; dz <= 1; dz++)
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{
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for (int dy = -1; dy <= 1; dy++)
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{
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for (int dx = -1; dx <= 1; dx++)
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{
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float3 neighbor = cell + float3(dx, dy, dz);
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int3 hash = cultmath_pcg3d(neighbor);
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float3 jitter = float3(
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(uint)hash.x * (1.0 / 4294967296.0),
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(uint)hash.y * (1.0 / 4294967296.0),
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(uint)hash.z * (1.0 / 4294967296.0));
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float3 feature = neighbor + jitter;
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float d = cultmath_distance(p, feature);
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if (d < f1)
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{
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f2 = f1; c2 = c1;
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f1 = d; c1 = feature; hash1 = hash.x;
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}
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else if (d < f2)
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{
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f2 = d; c2 = feature;
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}
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}
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}
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}
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float3 grad1 = f1 > 0.0 ? (p - c1) / f1 : float3(0.0, 0.0, 0.0);
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float3 grad2 = f2 > 0.0 ? (p - c2) / f2 : float3(0.0, 0.0, 0.0);
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CultCellular result;
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result.nearest = float4(grad1, f1);
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result.edge = float4(grad2 - grad1, f2 - f1);
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result.id = (uint)hash1 * (1.0 / 4294967296.0);
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return result;
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}
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float cultmath_value_noise(float2 position)
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{
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float2 cell = floor(position);
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