HairCommon.h

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// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
// SPDX-FileCopyrightText: 2026 Jorrit Rouwe
// SPDX-License-Identifier: MIT
 
#include "ShaderMath.h"
#include "ShaderMat44.h"
#include "ShaderQuat.h"
#include "ShaderPlane.h"
#include "ShaderVec3.h"
 
// The density and velocity fields are stored in fixed point while accumulating, this constant converts from float to fixed point.
JPH_SHADER_CONSTANT(int, cFloatToFixed, 1 << 10)
JPH_SHADER_CONSTANT(float, cFixedToFloat, 1.0f / float(cFloatToFixed))
 
bool IsVertexFixed(JPH_SHADER_BUFFER(JPH_uint) inVertexFixed, uint inVertexIndex)
{
    return (inVertexFixed[inVertexIndex >> 5] & (1u << (inVertexIndex & 31))) != 0;
}
 
float GetVertexInvMass(JPH_SHADER_BUFFER(JPH_uint) inVertexFixed, uint inVertexIndex)
{
    return IsVertexFixed(inVertexFixed, inVertexIndex)? 0.0f : 1.0f;
}
 
float GetVertexStrandFraction(JPH_SHADER_BUFFER(JPH_uint) inStrandFractions, uint inVertexIndex)
{
    return ((inStrandFractions[inVertexIndex >> 2] >> ((inVertexIndex & 3) << 3)) & 0xff) * (1.0f / 255.0f);
}
 
uint GetStrandVertexCount(JPH_SHADER_BUFFER(JPH_uint) inStrandVertexCounts, uint inStrandIndex)
{
    return (inStrandVertexCounts[inStrandIndex >> 2] >> ((inStrandIndex & 3) << 3)) & 0xff;
}
 
uint GetStrandMaterialIndex(JPH_SHADER_BUFFER(JPH_uint) inStrandMaterialIndex, uint inStrandIndex)
{
    return (inStrandMaterialIndex[inStrandIndex >> 2] >> ((inStrandIndex & 3) << 3)) & 0xff;
}
 
float GradientSamplerSample(float4 inSampler, float inStrandFraction)
{
    return min(inSampler.w, max(inSampler.z, inSampler.y + inStrandFraction * inSampler.x));
}
 
void GridPositionToIndexAndFraction(float3 inPosition, JPH_OUT(uint3) outIndex, JPH_OUT(float3) outFraction)
{
    // Get position in grid space
    float3 grid_pos = min(max(inPosition - cGridOffset, float3(0, 0, 0)) * cGridScale, cGridSizeMin1);
    outIndex = min(uint3(grid_pos), cGridSizeMin2);
    outFraction = grid_pos - float3(outIndex);
}
 
uint GridIndexToBufferIndex(uint3 inIndex)
{
    return inIndex.x + inIndex.y * cGridStride.y + inIndex.z * cGridStride.z;
}