void
simpleFluidEmitter::surfaceFluidEmitter(
MFnFluid& fluid,
const MMatrix& fluidWorldMatrix,
int plugIndex,
MDataBlock& block,
double dt,
double conversion,
double dropoff
)
//==============================================================================
//
// Method:
//
// simpleFluidEmitter::surfaceFluidEmitter
//
// Description:
//
// Emits fluid from one of a predefined set of volumes (cube, sphere,
// cylinder, cone, torus).
//
// Parameters:
//
// fluid: fluid into which we are emitting
// fluidWorldMatrix: object->world matrix for the fluid
// plugIndex: identifies which fluid connected to the emitter
// we are emitting into
// block: datablock for the emitter, to retrieve attribute
// values
// dt: time delta for this frame
// conversion: mapping from UI emission rates to internal units
// dropoff: specifies how much emission rate drops off as
// the surface points move away from the centers
// of the voxels in which they lie.
//
// Notes:
//
// To associate an owner object with an emitter, use the
// addDynamic MEL command, e.g. "addDynamic simpleFluidEmitter1 pPlane1".
//
//==============================================================================
{
// get relevant world matrices
//
MMatrix fluidInverseWorldMatrix = fluidWorldMatrix.inverse();
// get emission rates for density, fuel, heat, and emission color
//
double densityEmit = fluidDensityEmission( block );
double fuelEmit = fluidFuelEmission( block );
double heatEmit = fluidHeatEmission( block );
bool doEmitColor = fluidEmitColor( block );
MColor emitColor = fluidColor( block );
// rate modulation based on frame time, user value conversion factor, and
// standard emitter "rate" value (not actually exposed in most fluid
// emitters, but there anyway).
//
double theRate = getRate(block) * dt * conversion;
// get voxel dimensions and sizes (object space)
//
double size[3];
unsigned int res[3];
fluid.getDimensions( size[0], size[1], size[2] );
fluid.getResolution( res[0], res[1], res[2] );
// voxel sizes
double dx = size[0] / res[0];
double dy = size[1] / res[1];
double dz = size[2] / res[2];
// voxel centers
double Ox = -size[0]/2;
double Oy = -size[1]/2;
double Oz = -size[2]/2;
// get the "swept geometry" data for the emitter surface. This structure
// tracks the motion of each emitter triangle over the time interval
// for this simulation step. We just use positions on the emitter
// surface at the end of the time step to do the emission.
//
MDataHandle sweptHandle = block.inputValue( mSweptGeometry );
MObject sweptData = sweptHandle.data();
MFnDynSweptGeometryData fnSweptData( sweptData );
// for "non-jittered" sampling, just reset the random state for each
// triangle, which gives us a fixed set of samples all the time.
// Sure, they're still jittered, but they're all jittered the same,
// which makes them kinda uniform.
//
bool jitter = fluidJitter(block);
if( !jitter )
{
resetRandomState( plugIndex, block );
}
if( fnSweptData.triangleCount() > 0 )
{
// average voxel face area - use this as the canonical unit that
// receives the emission rate specified by the users. Scale the
// rate for other triangles accordingly.
//
double vfArea = pow(dx*dy*dz, 2.0/3.0);
// very rudimentary support for textured emission rate and
// textured emission color. We simply sample each texture once
// at the center of each emitter surface triangle. This will
// cause aliasing artifacts when these triangles are large.
//
MFnDependencyNode fnNode( thisMObject() );
MObject rateTextureAttr = fnNode.attribute( "textureRate" );
MObject colorTextureAttr = fnNode.attribute( "particleColor" );
bool texturedRate = hasValidEmission2dTexture( rateTextureAttr );
bool texturedColor = hasValidEmission2dTexture( colorTextureAttr );
// construct texture coordinates for each triangle center
//
MDoubleArray uCoords, vCoords;
if( texturedRate || texturedColor )
{
uCoords.setLength( fnSweptData.triangleCount() );
vCoords.setLength( fnSweptData.triangleCount() );
int t;
for( t = 0; t < fnSweptData.triangleCount(); t++ )
{
MDynSweptTriangle tri = fnSweptData.sweptTriangle( t );
MVector uv0 = tri.uvPoint(0);
MVector uv1 = tri.uvPoint(1);
MVector uv2 = tri.uvPoint(2);
MVector uvMid = (uv0+uv1+uv2)/3.0;
uCoords[t] = uvMid[0];
vCoords[t] = uvMid[1];
}
}
// evaluate textured rate and color values at the triangle centers
//
MDoubleArray texturedRateValues;
if( texturedRate )
{
texturedRateValues.setLength( uCoords.length() );
evalEmission2dTexture( rateTextureAttr, uCoords, vCoords, NULL, &texturedRateValues );
}
MVectorArray texturedColorValues;
if( texturedColor )
{
texturedColorValues.setLength( uCoords.length() );
evalEmission2dTexture( colorTextureAttr, uCoords, vCoords, &texturedColorValues, NULL );
}
for( int t = 0; t < fnSweptData.triangleCount(); t++ )
{
// calculate emission rate and color values for this triangle
//
double curTexturedRate = texturedRate ? texturedRateValues[t] : 1.0;
MColor curTexturedColor;
if( texturedColor )
{
MVector& curVec = texturedColorValues[t];
curTexturedColor.r = (float)curVec[0];
curTexturedColor.g = (float)curVec[1];
curTexturedColor.b = (float)curVec[2];
curTexturedColor.a = 1.0;
}
else
{
curTexturedColor = emitColor;
}
MDynSweptTriangle tri = fnSweptData.sweptTriangle( t );
MVector v0 = tri.vertex(0);
MVector v1 = tri.vertex(1);
MVector v2 = tri.vertex(2);
// compute number of samples for this triangle based on area,
// with large triangles receiving approximately 1 sample for
// each voxel that they intersect
//
double triArea = tri.area();
int numSamples = (int)(triArea / vfArea);
if( numSamples < 1 ) numSamples = 1;
// compute emission rate for the points on the triangle.
// Scale the canonical rate by the area ratio of this triangle
// to the average voxel size, then split it amongst all the samples.
//
double triRate = (theRate*(triArea/vfArea))/numSamples;
triRate *= curTexturedRate;
for( int j = 0; j < numSamples; j++ )
{
// generate a random point on the triangle,
// map it into fluid local space
//
double r1 = randgen();
double r2 = randgen();
if( r1 + r2 > 1 )
{
r1 = 1-r1;
r2 = 1-r2;
}
double r3 = 1 - (r1+r2);
MPoint randPoint = r1*v0 + r2*v1 + r3*v2;
randPoint *= fluidInverseWorldMatrix;
// figure out where the current point lies
//
::int3 coord;
fluid.toGridIndex( randPoint, coord );
if( (coord[0]<0) || (coord[1]<0) || (coord[2]<0) ||
(coord[0]>=(int)res[0]) || (coord[1]>=(int)res[1]) || (coord[2]>=(int)res[2]) )
{
continue;
}
// do some falloff based on how far from the voxel center
// the current point lies
//
MPoint gridPoint;
gridPoint.x = Ox + (coord[0]+0.5)*dx;
gridPoint.y = Oy + (coord[1]+0.5)*dy;
gridPoint.z = Oz + (coord[2]+0.5)*dz;
MVector diff = gridPoint - randPoint;
double distSquared = diff * diff;
double distDrop = dropoff * distSquared;
double newVal = triRate * exp( -distDrop );
// emit into the voxel
//
if( newVal != 0 )
{
fluid.emitIntoArrays( (float) newVal, coord[0], coord[1], coord[2], (float)densityEmit, (float)heatEmit, (float)fuelEmit, doEmitColor, curTexturedColor );
}
}
}
}
}
void
simpleFluidEmitter::volumeFluidEmitter(
MFnFluid& fluid,
const MMatrix& fluidWorldMatrix,
int plugIndex,
MDataBlock& block,
double dt,
double conversion,
double dropoff
)
//==============================================================================
//
// Method:
//
// simpleFluidEmitter::volumeFluidEmitter
//
// Description:
//
// Emits fluid from points distributed over the surface of the
// emitter's owner object.
//
// Parameters:
//
// fluid: fluid into which we are emitting
// fluidWorldMatrix: object->world matrix for the fluid
// plugIndex: identifies which fluid connected to the emitter
// we are emitting into
// block: datablock for the emitter, to retrieve attribute
// values
// dt: time delta for this frame
// conversion: mapping from UI emission rates to internal units
// dropoff: specifies how much emission rate drops off as
// we move away from the local y-axis of the
// volume emitter shape.
//
//==============================================================================
{
// get emitter position and relevant matrices
//
MPoint emitterPos = getWorldPosition();
MMatrix emitterWorldMatrix = getWorldMatrix();
MMatrix fluidInverseWorldMatrix = fluidWorldMatrix.inverse();
// get emission rates for density, fuel, heat, and emission color
//
double densityEmit = fluidDensityEmission( block );
double fuelEmit = fluidFuelEmission( block );
double heatEmit = fluidHeatEmission( block );
bool doEmitColor = fluidEmitColor( block );
MColor emitColor = fluidColor( block );
// rate modulation based on frame time, user value conversion factor, and
// standard emitter "rate" value (not actually exposed in most fluid
// emitters, but there anyway).
//
double theRate = getRate(block) * dt * conversion;
// get voxel dimensions and sizes (object space)
//
double size[3];
unsigned int res[3];
fluid.getDimensions( size[0], size[1], size[2] );
fluid.getResolution( res[0], res[1], res[2] );
// voxel sizes
double dx = size[0] / res[0];
double dy = size[1] / res[1];
double dz = size[2] / res[2];
// voxel centers
double Ox = -size[0]/2;
double Oy = -size[1]/2;
double Oz = -size[2]/2;
// find the voxels that intersect the bounding box of the volume
// primitive associated with the emitter
//
MBoundingBox bbox;
if( !volumePrimitiveBoundingBox( bbox ) )
{
// shouldn't happen
//
return;
}
// transform volume primitive into fluid space
//
bbox.transformUsing( emitterWorldMatrix );
bbox.transformUsing( fluidInverseWorldMatrix );
MPoint lowCorner = bbox.min();
MPoint highCorner = bbox.max();
// get fluid voxel coord range of bounding box
//
::int3 lowCoords;
::int3 highCoords;
fluid.toGridIndex( lowCorner, lowCoords );
fluid.toGridIndex( highCorner, highCoords );
int i;
for ( i = 0; i < 3; i++ )
{
if ( lowCoords[i] < 0 ) {
lowCoords[i] = 0;
} else if ( lowCoords[i] > ((int)res[i])-1 ) {
lowCoords[i] = ((int)res[i])-1;
}
if ( highCoords[i] < 0 ) {
highCoords[i] = 0;
} else if ( highCoords[i] > ((int)res[i])-1 ) {
highCoords[i] = ((int)res[i])-1;
}
}
// figure out the emitter size relative to the voxel size, and compute
// a per-voxel sampling rate that uses 1 sample/voxel for emitters that
// are >= 2 voxels big in all dimensions. For smaller emitters, use up
// to 8 samples per voxel.
//
double emitterVoxelSize[3];
emitterVoxelSize[0] = (highCorner[0]-lowCorner[0])/dx;
emitterVoxelSize[1] = (highCorner[1]-lowCorner[1])/dy;
emitterVoxelSize[2] = (highCorner[2]-lowCorner[2])/dz;
double minVoxelSize = MIN(emitterVoxelSize[0],MIN(emitterVoxelSize[1],emitterVoxelSize[2]));
if( minVoxelSize < 1.0 )
{
minVoxelSize = 1.0;
}
int maxSamples = 8;
int numSamples = (int)(8.0/(minVoxelSize*minVoxelSize*minVoxelSize) + 0.5);
if( numSamples < 1 ) numSamples = 1;
if( numSamples > maxSamples ) numSamples = maxSamples;
// non-jittered, just use one sample in the voxel center. Should replace
// with uniform sampling pattern.
//
bool jitter = fluidJitter(block);
if( !jitter )
{
numSamples = 1;
}
// for each voxel that could potentially intersect the volume emitter
// primitive, take some samples in the voxel. For those inside the
// volume, compute their dropoff relative to the primitive's local y-axis,
// and emit an appropriate amount into the voxel.
//
for( i = lowCoords[0]; i <= highCoords[0]; i++ )
{
double x = Ox + (i+0.5)*dx;
for( int j = lowCoords[1]; j < highCoords[1]; j++ )
{
double y = Oy + (j+0.5)*dy;
for( int k = lowCoords[2]; k < highCoords[2]; k++ )
{
double z = Oz + (k+0.5)*dz;
for ( int si = 0; si < numSamples; si++) {
// compute voxel sample point (object space)
//
double rx, ry, rz;
if(jitter) {
rx = x + dx*(randgen() - 0.5);
ry = y + dy*(randgen() - 0.5);
rz = z + dz*(randgen() - 0.5);
} else {
rx = x;
ry = y;
rz = z;
}
// to world space
MPoint pt( rx, ry, rz );
pt *= fluidWorldMatrix;
// test to see if point is inside volume primitive
//
if( volumePrimitivePointInside( pt, emitterWorldMatrix ) )
{
// compute dropoff
//
double dist = pt.distanceTo( emitterPos );
double distDrop = dropoff * (dist*dist);
double newVal = (theRate * exp( -distDrop )) / (double)numSamples;
// emit into arrays
//
if( newVal != 0.0 )
{
fluid.emitIntoArrays( (float) newVal, i, j, k, (float)densityEmit, (float)heatEmit, (float)fuelEmit, doEmitColor, emitColor );
}
}
}
}
}
}
}