public static void SimulateParticleSpawn(IPartSysExternal external, PartSysEmitter emitter, int particleIdx,
float timeToSimulate)
{
var spec = emitter.GetSpec();
var partSpawnTime = emitter.GetParticleSpawnTime(particleIdx);
var worldPosVar = emitter.GetWorldPosVar();
var particleX = worldPosVar.X;
var particleY = worldPosVar.Y;
var particleZ = worldPosVar.Z;
var emitOffsetX = GetParticleValue(emitter, particleIdx, PartSysParamId.emit_offset_X, partSpawnTime);
var emitOffsetY = GetParticleValue(emitter, particleIdx, PartSysParamId.emit_offset_Y, partSpawnTime);
var emitOffsetZ = GetParticleValue(emitter, particleIdx, PartSysParamId.emit_offset_Z, partSpawnTime);
if (spec.GetOffsetCoordSys() == PartSysCoordSys.Polar)
{
var coords = SphericalDegToCartesian(emitOffsetX, emitOffsetY, emitOffsetZ);
particleX += coords.X;
particleY += coords.Y;
particleZ += coords.Z;
}
else
{
particleX += emitOffsetX;
particleY += emitOffsetY;
particleZ += emitOffsetZ;
}
switch (spec.GetSpace())
{
case PartSysEmitterSpace.ObjectPos:
case PartSysEmitterSpace.ObjectYpr:
{
if (spec.GetParticleSpace() != PartSysParticleSpace.SameAsEmitter)
{
// TODO: Figure out this formula...
var scale = 1.0f - emitter.GetParticleAge(particleIdx) / timeToSimulate;
var prevObjPos = emitter.GetPrevObjPos();
var objPos = emitter.GetObjPos();
var dX = prevObjPos.X + (objPos.X - prevObjPos.X) * scale;
var dY = prevObjPos.Y + (objPos.Y - prevObjPos.Y) * scale;
var dZ = prevObjPos.Z + (objPos.Z - prevObjPos.Z) * scale;
var rotation = 0.0f;
if (spec.GetSpace() == PartSysEmitterSpace.ObjectYpr)
{
rotation = emitter.GetPrevObjRotation() +
(emitter.GetObjRotation() - emitter.GetPrevObjRotation()) * scale;
}
RotateAndMove(dX, dY, dZ, rotation, ref particleX, ref particleY, ref particleZ);
}
}
break;
case PartSysEmitterSpace.Bones:
{
var scale = 1.0f - emitter.GetParticleAge(particleIdx) / timeToSimulate;
if (emitter.GetBoneState() == null)
{
break;
}
if (emitter.GetBoneState().GetRandomPos(scale, out var bonePos))
{
particleX = bonePos.X;
particleY = bonePos.Y;
particleZ = bonePos.Z;
}
}
break;
case PartSysEmitterSpace.NodePos:
case PartSysEmitterSpace.NodeYpr:
{
if (spec.GetParticleSpace() != PartSysParticleSpace.SameAsEmitter)
{
var scale = 1.0f - emitter.GetParticleAge(particleIdx) / timeToSimulate;
if (spec.GetSpace() == PartSysEmitterSpace.NodeYpr)
{
if (!external.GetBoneWorldMatrix(emitter.GetAttachedTo(), spec.GetNodeName(),
out var boneM))
{
boneM = Matrix4x4.Identity;
}
var ppos = new Vector3(particleX, particleY, particleZ);
var newpos = Vector3.Transform(ppos, boneM);
particleX = newpos.X;
particleY = newpos.Y;
particleZ = newpos.Z;
}
else
{
var prevObjPos = emitter.GetPrevObjPos();
var objPos = emitter.GetObjPos();
var dX = prevObjPos.X + (objPos.X - prevObjPos.X) * scale;
var dY = prevObjPos.Y + (objPos.Y - prevObjPos.Y) * scale;
var dZ = prevObjPos.Z + (objPos.Z - prevObjPos.Z) * scale;
RotateAndMove(dX, dY, dZ, 0.0f, ref particleX, ref particleY, ref particleZ);
}
}
}
break;
default:
break;
}
var state = emitter.GetParticleState();
state.SetState(ParticleStateField.PSF_X, particleIdx, particleX);
state.SetState(ParticleStateField.PSF_Y, particleIdx, particleY);
state.SetState(ParticleStateField.PSF_Z, particleIdx, particleZ);
// Initialize particle color
SetParticleParam(emitter, particleIdx, PartSysParamId.emit_init_red, partSpawnTime,
ParticleStateField.PSF_RED, 255.0f);
SetParticleParam(emitter, particleIdx, PartSysParamId.emit_init_green, partSpawnTime,
ParticleStateField.PSF_GREEN, 255.0f);
SetParticleParam(emitter, particleIdx, PartSysParamId.emit_init_blue, partSpawnTime,
ParticleStateField.PSF_BLUE, 255.0f);
SetParticleParam(emitter, particleIdx, PartSysParamId.emit_init_alpha, partSpawnTime,
ParticleStateField.PSF_ALPHA, 255.0f);
// Initialize particle velocity
var partVelX = GetParticleValue(emitter, particleIdx, PartSysParamId.emit_init_vel_X, partSpawnTime);
var partVelY = GetParticleValue(emitter, particleIdx, PartSysParamId.emit_init_vel_Y, partSpawnTime);
var partVelZ = GetParticleValue(emitter, particleIdx, PartSysParamId.emit_init_vel_Z, partSpawnTime);
if (spec.GetSpace() == PartSysEmitterSpace.ObjectYpr)
{
if (spec.GetParticleSpace() != PartSysParticleSpace.SameAsEmitter)
{
var scale = 1.0f - emitter.GetParticleAge(particleIdx) / timeToSimulate;
var rotation = 0.0f;
if (spec.GetSpace() == PartSysEmitterSpace.ObjectYpr)
{
rotation = (emitter.GetObjRotation() - emitter.GetPrevObjRotation()) * scale +
emitter.GetPrevObjRotation();
}
// Rotate the velocity vector according to the current object rotation in the world
// TODO: Even for rotation == 0, this will flip the velocity vector
Rotate2D(rotation, ref partVelX, ref partVelZ);
}
}
else if (spec.GetSpace() == PartSysEmitterSpace.NodeYpr)
{
if (spec.GetParticleSpace() != PartSysParticleSpace.SameAsEmitter)
{
var objId = emitter.GetAttachedTo();
if (!external.GetBoneWorldMatrix(objId, spec.GetNodeName(), out var boneMatrix))
{
boneMatrix = Matrix4x4.Identity;
}
// Construct a directional vector (not a positional one, w=0 here) for the velocity
var dirVec = new Vector3(partVelX, partVelY, partVelZ);
dirVec = Vector3.TransformNormal(dirVec, boneMatrix);
partVelX = dirVec.X;
partVelY = dirVec.Y;
partVelZ = dirVec.Z;
}
}
// Are particle coordinates defined as polar coordinates? Convert them to cartesian here
if (spec.GetParticleVelocityCoordSys() == PartSysCoordSys.Polar)
{
var cartesianVel = SphericalDegToCartesian(partVelX, partVelY, partVelZ);
partVelX = cartesianVel.X;
partVelY = cartesianVel.Y;
partVelZ = cartesianVel.Z;
}
state.SetState(ParticleStateField.PSF_VEL_X, particleIdx, partVelX);
state.SetState(ParticleStateField.PSF_VEL_Y, particleIdx, partVelY);
state.SetState(ParticleStateField.PSF_VEL_Z, particleIdx, partVelZ);
// I don't know why it's taken at lifetime 0.
// TODO: Figure out if this actually *never* changes?
var posVarX = GetParticleValue(emitter, particleIdx, PartSysParamId.part_posVariation_X, 0);
var posVarY = GetParticleValue(emitter, particleIdx, PartSysParamId.part_posVariation_Y, 0);
var posVarZ = GetParticleValue(emitter, particleIdx, PartSysParamId.part_posVariation_Z, 0);
// For a polar system, convert these positions to cartesian to apply them to the
// rendering position
if (spec.GetParticlePosCoordSys() == PartSysCoordSys.Polar)
{
state.SetState(ParticleStateField.PSF_POS_AZIMUTH, particleIdx, 0);
state.SetState(ParticleStateField.PSF_POS_INCLINATION, particleIdx, 0);
state.SetState(ParticleStateField.PSF_POS_RADIUS, particleIdx, 0);
// Convert to cartesian and add to the actual current particle position
// As usual, x, y, z here are (azimuth, inclination, radius)
var cartesianPos = SphericalDegToCartesian(posVarX, posVarY, posVarZ);
posVarX = cartesianPos.X;
posVarY = cartesianPos.Y;
posVarZ = cartesianPos.Z;
}
// Apply the position variation to the initial position and store it
posVarX += particleX;
posVarY += particleY;
posVarZ += particleZ;
state.SetState(ParticleStateField.PSF_POS_VAR_X, particleIdx, posVarX);
state.SetState(ParticleStateField.PSF_POS_VAR_Y, particleIdx, posVarY);
state.SetState(ParticleStateField.PSF_POS_VAR_Z, particleIdx, posVarZ);
/*
* The following code will apply particle movement after
* spawning a particle retroactively. This should only happen
* for high frequency particle systems that spawn multiple particles
* per frame.
* Also note how particle age instead of particle lifetime is used here
* to access parameters of the emitter.
*/
var partAge = emitter.GetParticleAge(particleIdx);
if (partAge != 0)
{
var partAgeSquared = partAge * partAge;
particleX += partVelX * partAge;
particleY += partVelY * partAge;
particleZ += partVelZ * partAge;
var param = emitter.GetParamState(PartSysParamId.part_accel_X);
if (param != null)
{
var accelX = param.GetValue(emitter, particleIdx, partAge);
particleX += accelX * partAgeSquared * 0.5f;
partVelX += accelX * partAge;
}
param = emitter.GetParamState(PartSysParamId.part_accel_Y);
if (param != null)
{
var accelY = param.GetValue(emitter, particleIdx, partAge);
particleY += accelY * partAgeSquared * 0.5f;
partVelY += accelY * partAge;
}
param = emitter.GetParamState(PartSysParamId.part_accel_Z);
if (param != null)
{
var accelZ = param.GetValue(emitter, particleIdx, partAge);
particleZ += accelZ * partAgeSquared * 0.5f;
partVelZ += accelZ * partAge;
}
state.SetState(ParticleStateField.PSF_VEL_X, particleIdx, partVelX);
state.SetState(ParticleStateField.PSF_VEL_Y, particleIdx, partVelY);
state.SetState(ParticleStateField.PSF_VEL_Z, particleIdx, partVelZ);
param = emitter.GetParamState(PartSysParamId.part_velVariation_X);
if (param != null)
{
particleX += param.GetValue(emitter, particleIdx, partAge) * partAge;
}
param = emitter.GetParamState(PartSysParamId.part_velVariation_Y);
if (param != null)
{
particleY += param.GetValue(emitter, particleIdx, partAge) * partAge;
}
param = emitter.GetParamState(PartSysParamId.part_velVariation_Z);
if (param != null)
{
particleZ += param.GetValue(emitter, particleIdx, partAge) * partAge;
}
state.SetState(ParticleStateField.PSF_X, particleIdx, particleX);
state.SetState(ParticleStateField.PSF_Y, particleIdx, particleY);
state.SetState(ParticleStateField.PSF_Z, particleIdx, particleZ);
}
// Simulate rotation for anything other than a point particle
if (spec.GetParticleType() != PartSysParticleType.Point)
{
var emitterAge = emitter.GetParticleSpawnTime(particleIdx);
var rotation = emitter.GetParamValue(PartSysParamId.emit_yaw, particleIdx, emitterAge, 0.0f);
emitter.GetParticleState().SetState(ParticleStateField.PSF_ROTATION, particleIdx, rotation);
}
}