forked from LeenkxTeam/LNXSDK
65 lines
3.0 KiB
C
65 lines
3.0 KiB
C
// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
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// SPDX-FileCopyrightText: 2026 Jorrit Rouwe
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// SPDX-License-Identifier: MIT
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#include "HairApplyGlobalPose.h"
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void ApplyCollisionAndUpdateVelocity(uint inVtx, JPH_IN_OUT(JPH_HairPosition) ioPos, JPH_IN(JPH_HairPosition) inPreviousPos, JPH_IN(JPH_HairMaterial) inMaterial, float inStrandFraction, JPH_OUT(JPH_HairVelocity) outVel)
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{
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// Update velocities
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outVel.mVelocity = (ioPos.mPosition - inPreviousPos.mPosition) / cDeltaTime;
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outVel.mAngularVelocity = cTwoDivDeltaTime * JPH_QuatMulQuat(ioPos.mRotation, JPH_QuatConjugate(inPreviousPos.mRotation)).xyz;
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if (inMaterial.mEnableCollision)
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{
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// Calculate closest point on the collision plane
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JPH_HairCollisionPlane plane = gCollisionPlanes[inVtx];
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float distance_to_plane = JPH_PlaneSignedDistance(plane.mPlane, ioPos.mPosition);
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float3 contact_normal = JPH_PlaneGetNormal(plane.mPlane);
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float3 point_on_plane = ioPos.mPosition - distance_to_plane * contact_normal;
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// Calculate how much the plane moved in this time step
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JPH_HairCollisionShape shape = gCollisionShapes[plane.mShapeIndex];
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float3 plane_velocity = shape.mLinearVelocity + cross(shape.mAngularVelocity, point_on_plane - shape.mCenterOfMass);
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float plane_movement = dot(plane_velocity, contact_normal) * cAccumulatedDeltaTime;
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float projected_distance = -distance_to_plane + plane_movement + GradientSamplerSample(inMaterial.mHairRadius, inStrandFraction);
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if (projected_distance > 0.0f)
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{
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// Resolve penetration
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ioPos.mPosition += contact_normal * projected_distance;
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// Only update velocity when moving towards each other
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float3 v_relative = outVel.mVelocity - plane_velocity;
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float v_relative_dot_normal = dot(contact_normal, v_relative);
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if (v_relative_dot_normal < 0.0f)
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{
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// Calculate normal and tangential velocity (equation 30)
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float3 v_normal = contact_normal * v_relative_dot_normal;
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float3 v_tangential = v_relative - v_normal;
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float v_tangential_length = length(v_tangential);
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// Apply friction as described in Detailed Rigid Body Simulation with Extended Position Based Dynamics - Matthias Muller et al. (modified equation 31)
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if (v_tangential_length > 0.0f)
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outVel.mVelocity -= v_tangential * min(inMaterial.mFriction * projected_distance / (v_tangential_length * cDeltaTime), 1.0f);
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// Apply restitution of zero (equation 35)
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outVel.mVelocity -= v_normal;
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}
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}
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}
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}
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void LimitVelocity(JPH_IN_OUT(JPH_HairVelocity) ioVel, JPH_IN(JPH_HairMaterial) inMaterial)
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{
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// Limit linear velocity
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float linear_velocity_sq = dot(ioVel.mVelocity, ioVel.mVelocity);
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if (linear_velocity_sq > inMaterial.mMaxLinearVelocitySq)
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ioVel.mVelocity *= sqrt(inMaterial.mMaxLinearVelocitySq / linear_velocity_sq);
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// Limit angular velocity
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float angular_velocity_sq = dot(ioVel.mAngularVelocity, ioVel.mAngularVelocity);
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if (angular_velocity_sq > inMaterial.mMaxAngularVelocitySq)
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ioVel.mAngularVelocity *= sqrt(inMaterial.mMaxAngularVelocitySq / angular_velocity_sq);
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}
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