HairApplyGlobalPose.h

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// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
// SPDX-FileCopyrightText: 2026 Jorrit Rouwe
// SPDX-License-Identifier: MIT
 
void ApplyGlobalPose(JPH_IN_OUT(JPH_HairPosition) ioPos, float3 inRestPosition, JPH_Quat inRestOrientation, JPH_IN(JPH_HairGlobalPoseTransform) inGlobalPoseTransform, JPH_IN(JPH_HairMaterial) inMaterial, float inStrandFraction)
{
    // LERP between stored global pose and global pose skinned to the scalp
    float skin_factor = GradientSamplerSample(inMaterial.mSkinGlobalPose, inStrandFraction);
    float3 in_position = inRestPosition;
    in_position += skin_factor * (inGlobalPoseTransform.mPosition + JPH_QuatMulVec3(inGlobalPoseTransform.mRotation, in_position) - in_position);
    JPH_Quat in_rotation = inRestOrientation;
    in_rotation += skin_factor * (JPH_QuatMulQuat(inGlobalPoseTransform.mRotation, in_rotation) - in_rotation);
 
    // LERP between simulated position and skinned position
    float pose_factor = GradientSamplerSample(inMaterial.mGlobalPose, inStrandFraction);
    ioPos.mPosition += pose_factor * (in_position - ioPos.mPosition);
    ioPos.mRotation += pose_factor * (in_rotation - ioPos.mRotation);
    ioPos.mRotation = normalize(ioPos.mRotation);
}