public void Execute()
{
for (int i = 0; i < contacts.Length; ++i)
{
var contact = contacts[i];
// Get the indices of the particle and collider involved in this contact:
int simplexStart = simplexCounts.GetSimplexStartAndSize(contact.bodyA, out int simplexSize);
int colliderIndex = contact.bodyB;
// Skip contacts involving triggers:
if (shapes[colliderIndex].flags > 0)
{
continue;
}
// Get the rigidbody index (might be < 0, in that case there's no rigidbody present)
int rigidbodyIndex = shapes[colliderIndex].rigidbodyIndex;
// Combine collision materials (use material from first particle in simplex)
BurstCollisionMaterial material = CombineCollisionMaterials(simplices[simplexStart], colliderIndex);
// Calculate relative velocity:
float4 rA = float4.zero, rB = float4.zero;
float4 prevPositionA = float4.zero;
float4 linearVelocityA = float4.zero;
float4 angularVelocityA = float4.zero;
float4 invInertiaTensorA = float4.zero;
quaternion orientationA = new quaternion(0, 0, 0, 0);
float simplexRadiusA = 0;
for (int j = 0; j < simplexSize; ++j)
{
int particleIndex = simplices[simplexStart + j];
prevPositionA += prevPositions[particleIndex] * contact.pointA[j];
linearVelocityA += BurstIntegration.DifferentiateLinear(positions[particleIndex], prevPositions[particleIndex], substepTime) * contact.pointA[j];
angularVelocityA += BurstIntegration.DifferentiateAngular(orientations[particleIndex], prevOrientations[particleIndex], substepTime) * contact.pointA[j];
invInertiaTensorA += invInertiaTensors[particleIndex] * contact.pointA[j];
orientationA.value += orientations[particleIndex].value * contact.pointA[j];
simplexRadiusA += BurstMath.EllipsoidRadius(contact.normal, prevOrientations[particleIndex], radii[particleIndex].xyz) * contact.pointA[j];
}
float4 relativeVelocity = linearVelocityA;
// Add particle angular velocity if rolling contacts are enabled:
if (material.rollingContacts > 0)
{
rA = -contact.normal * simplexRadiusA;
relativeVelocity += new float4(math.cross(angularVelocityA.xyz, rA.xyz), 0);
}
// Subtract rigidbody velocity:
if (rigidbodyIndex >= 0)
{
// Note: unlike rA, that is expressed in solver space, rB is expressed in world space.
rB = inertialFrame.frame.TransformPoint(contact.pointB) - rigidbodies[rigidbodyIndex].com;
relativeVelocity -= BurstMath.GetRigidbodyVelocityAtPoint(rigidbodyIndex, contact.pointB, rigidbodies, rigidbodyLinearDeltas, rigidbodyAngularDeltas, inertialFrame.frame);
}
// Determine impulse magnitude:
float2 impulses = contact.SolveFriction(relativeVelocity, material.staticFriction, material.dynamicFriction, stepTime);
if (math.abs(impulses.x) > BurstMath.epsilon || math.abs(impulses.y) > BurstMath.epsilon)
{
float4 tangentImpulse = impulses.x * contact.tangent;
float4 bitangentImpulse = impulses.y * contact.bitangent;
float4 totalImpulse = tangentImpulse + bitangentImpulse;
float baryScale = BurstMath.BaryScale(contact.pointA);
for (int j = 0; j < simplexSize; ++j)
{
int particleIndex = simplices[simplexStart + j];
//(tangentImpulse * contact.tangentInvMassA + bitangentImpulse * contact.bitangentInvMassA) * dt;
deltas[particleIndex] += (tangentImpulse * contact.tangentInvMassA + bitangentImpulse * contact.bitangentInvMassA) * substepTime * contact.pointA[j] * baryScale;
counts[particleIndex]++;
}
if (rigidbodyIndex >= 0)
{
BurstMath.ApplyImpulse(rigidbodyIndex, -totalImpulse, contact.pointB, rigidbodies, rigidbodyLinearDeltas, rigidbodyAngularDeltas, inertialFrame.frame);
}
// Rolling contacts:
if (material.rollingContacts > 0)
{
// Calculate angular velocity deltas due to friction impulse:
float4x4 solverInertiaA = BurstMath.TransformInertiaTensor(invInertiaTensorA, orientationA);
float4 angVelDeltaA = math.mul(solverInertiaA, new float4(math.cross(rA.xyz, totalImpulse.xyz), 0));
float4 angVelDeltaB = float4.zero;
// Final angular velocities, after adding the deltas:
angularVelocityA += angVelDeltaA;
float4 angularVelocityB = float4.zero;
// Calculate weights (inverse masses):
float invMassA = math.length(math.mul(solverInertiaA, math.normalizesafe(angularVelocityA)));
float invMassB = 0;
if (rigidbodyIndex >= 0)
{
angVelDeltaB = math.mul(-rigidbodies[rigidbodyIndex].inverseInertiaTensor, new float4(math.cross(rB.xyz, totalImpulse.xyz), 0));
angularVelocityB = rigidbodies[rigidbodyIndex].angularVelocity + angVelDeltaB;
invMassB = math.length(math.mul(rigidbodies[rigidbodyIndex].inverseInertiaTensor, math.normalizesafe(angularVelocityB)));
}
// Calculate rolling axis and angular velocity deltas:
float4 rollAxis = float4.zero;
float rollingImpulse = contact.SolveRollingFriction(angularVelocityA, angularVelocityB, material.rollingFriction, invMassA, invMassB, ref rollAxis);
angVelDeltaA += rollAxis * rollingImpulse * invMassA;
angVelDeltaB -= rollAxis * rollingImpulse * invMassB;
// Apply orientation delta to particles:
quaternion orientationDelta = BurstIntegration.AngularVelocityToSpinQuaternion(orientationA, angVelDeltaA, substepTime);
for (int j = 0; j < simplexSize; ++j)
{
int particleIndex = simplices[simplexStart + j];
quaternion qA = orientationDeltas[particleIndex];
qA.value += orientationDelta.value;
orientationDeltas[particleIndex] = qA;
orientationCounts[particleIndex]++;
}
// Apply angular velocity delta to rigidbody:
if (rigidbodyIndex >= 0)
{
float4 angularDelta = rigidbodyAngularDeltas[rigidbodyIndex];
angularDelta += angVelDeltaB;
rigidbodyAngularDeltas[rigidbodyIndex] = angularDelta;
}
}
}
contacts[i] = contact;
}
}
public void Execute()
{
for (int i = 0; i < activeConstraintCount; ++i)
{
int particleIndex = particleIndices[i];
int colliderIndex = colliderIndices[i];
// no collider to pin to, so ignore the constraint.
if (colliderIndex < 0)
{
continue;
}
int rigidbodyIndex = shapes[colliderIndex].rigidbodyIndex;
// calculate time adjusted compliances
float2 compliances = stiffnesses[i].xy / (substepTime * substepTime);
// project particle position to the end of the full step:
float4 particlePosition = math.lerp(prevPositions[particleIndex], positions[particleIndex], substeps);
// express pin offset in world space:
float4 worldPinOffset = transforms[colliderIndex].TransformPoint(offsets[i]);
float4 predictedPinOffset = worldPinOffset;
quaternion predictedRotation = transforms[colliderIndex].rotation;
float rigidbodyLinearW = 0;
float rigidbodyAngularW = 0;
if (rigidbodyIndex >= 0)
{
var rigidbody = rigidbodies[rigidbodyIndex];
// predict offset point position:
float4 velocityAtPoint = BurstMath.GetRigidbodyVelocityAtPoint(rigidbodyIndex, inertialFrame.frame.InverseTransformPoint(worldPinOffset), rigidbodies, rigidbodyLinearDeltas, rigidbodyAngularDeltas, inertialFrame.frame);
predictedPinOffset = BurstIntegration.IntegrateLinear(predictedPinOffset, inertialFrame.frame.TransformVector(velocityAtPoint), stepTime);
// predict rotation at the end of the step:
predictedRotation = BurstIntegration.IntegrateAngular(predictedRotation, rigidbody.angularVelocity + rigidbodyAngularDeltas[rigidbodyIndex], stepTime);
// calculate linear and angular rigidbody weights:
rigidbodyLinearW = rigidbody.inverseMass;
rigidbodyAngularW = BurstMath.RotationalInvMass(rigidbody.inverseInertiaTensor,
worldPinOffset - rigidbody.com,
math.normalizesafe(inertialFrame.frame.TransformPoint(particlePosition) - predictedPinOffset));
}
// Transform pin position to solver space for constraint solving:
predictedPinOffset = inertialFrame.frame.InverseTransformPoint(predictedPinOffset);
predictedRotation = math.mul(math.conjugate(inertialFrame.frame.rotation), predictedRotation);
float4 gradient = particlePosition - predictedPinOffset;
float constraint = math.length(gradient);
float4 gradientDir = gradient / (constraint + BurstMath.epsilon);
float4 lambda = lambdas[i];
float linearDLambda = (-constraint - compliances.x * lambda.w) / (invMasses[particleIndex] + rigidbodyLinearW + rigidbodyAngularW + compliances.x + BurstMath.epsilon);
lambda.w += linearDLambda;
float4 correction = linearDLambda * gradientDir;
deltas[particleIndex] += correction * invMasses[particleIndex] / substeps;
counts[particleIndex]++;
if (rigidbodyIndex >= 0)
{
BurstMath.ApplyImpulse(rigidbodyIndex,
-correction / stepTime * 1,
inertialFrame.frame.InverseTransformPoint(worldPinOffset),
rigidbodies, rigidbodyLinearDeltas, rigidbodyAngularDeltas, inertialFrame.frame);
}
if (rigidbodyAngularW > 0 || invRotationalMasses[particleIndex] > 0)
{
// bend/twist constraint:
quaternion omega = math.mul(math.conjugate(orientations[particleIndex]), predictedRotation); //darboux vector
quaternion omega_plus;
omega_plus.value = omega.value + restDarboux[i].value; //delta Omega with - omega_0
omega.value -= restDarboux[i].value; //delta Omega with + omega_0
if (math.lengthsq(omega.value) > math.lengthsq(omega_plus.value))
{
omega = omega_plus;
}
float3 dlambda = (omega.value.xyz - compliances.y * lambda.xyz) / new float3(compliances.y + invRotationalMasses[particleIndex] + rigidbodyAngularW + BurstMath.epsilon);
lambda.xyz += dlambda;
//discrete Darboux vector does not have vanishing scalar part
quaternion dlambdaQ = new quaternion(dlambda[0], dlambda[1], dlambda[2], 0);
quaternion orientDelta = orientationDeltas[particleIndex];
orientDelta.value += math.mul(predictedRotation, dlambdaQ).value *invRotationalMasses[particleIndex] / substeps;
orientationDeltas[particleIndex] = orientDelta;
orientationCounts[particleIndex]++;
if (rigidbodyIndex >= 0)
{
BurstMath.ApplyDeltaQuaternion(rigidbodyIndex,
predictedRotation,
-math.mul(orientations[particleIndex], dlambdaQ).value *rigidbodyAngularW,
rigidbodyAngularDeltas, inertialFrame.frame, stepTime);
}
}
lambdas[i] = lambda;
}
}
public void Execute()
{
for (int i = 0; i < contacts.Length; ++i)
{
var contact = contacts[i];
int simplexStart = simplexCounts.GetSimplexStartAndSize(contact.bodyA, out int simplexSize);
int colliderIndex = contact.bodyB;
// Skip contacts involving triggers:
if (shapes[colliderIndex].flags > 0)
{
continue;
}
// Get the rigidbody index (might be < 0, in that case there's no rigidbody present)
int rigidbodyIndex = shapes[colliderIndex].rigidbodyIndex;
// Combine collision materials (use material from first particle in simplex)
BurstCollisionMaterial material = CombineCollisionMaterials(simplices[simplexStart], colliderIndex);
// Get relative velocity at contact point.
// As we do not consider true ellipses for collision detection, particle contact points are never off-axis.
// So particle angular velocity does not contribute to normal impulses, and we can skip it.
float4 simplexPosition = float4.zero;
float4 simplexPrevPosition = float4.zero;
float simplexRadius = 0;
for (int j = 0; j < simplexSize; ++j)
{
int particleIndex = simplices[simplexStart + j];
simplexPosition += positions[particleIndex] * contact.pointA[j];
simplexPrevPosition += prevPositions[particleIndex] * contact.pointA[j];
simplexRadius += BurstMath.EllipsoidRadius(contact.normal, orientations[particleIndex], radii[particleIndex].xyz) * contact.pointA[j];
}
// project position to the end of the full step:
float4 posA = math.lerp(simplexPrevPosition, simplexPosition, substeps);
posA += -contact.normal * simplexRadius;
float4 posB = contact.pointB;
if (rigidbodyIndex >= 0)
{
posB += BurstMath.GetRigidbodyVelocityAtPoint(rigidbodyIndex, contact.pointB, rigidbodies, rigidbodyLinearDeltas, rigidbodyAngularDeltas, inertialFrame.frame) * stepTime;
}
// adhesion:
float lambda = contact.SolveAdhesion(posA, posB, material.stickDistance, material.stickiness, stepTime);
// depenetration:
lambda += contact.SolvePenetration(posA, posB, solverParameters.maxDepenetration * stepTime);
// Apply normal impulse to both simplex and rigidbody:
if (math.abs(lambda) > BurstMath.epsilon)
{
float4 delta = lambda * contact.normal * BurstMath.BaryScale(contact.pointA) / substeps;
for (int j = 0; j < simplexSize; ++j)
{
int particleIndex = simplices[simplexStart + j];
deltas[particleIndex] += delta * invMasses[particleIndex] * contact.pointA[j];
counts[particleIndex]++;
}
// Apply position deltas immediately, if using sequential evaluation:
if (constraintParameters.evaluationOrder == Oni.ConstraintParameters.EvaluationOrder.Sequential)
{
for (int j = 0; j < simplexSize; ++j)
{
int particleIndex = simplices[simplexStart + j];
BurstConstraintsBatchImpl.ApplyPositionDelta(particleIndex, constraintParameters.SORFactor, ref positions, ref deltas, ref counts);
}
}
if (rigidbodyIndex >= 0)
{
BurstMath.ApplyImpulse(rigidbodyIndex, -lambda / stepTime * contact.normal, contact.pointB, rigidbodies, rigidbodyLinearDeltas, rigidbodyAngularDeltas, inertialFrame.frame);
}
}
contacts[i] = contact;
}
}