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 );
}
}
}
}
}
MStatus sweptEmitter::compute(const MPlug& plug, MDataBlock& block)
//
// Descriptions:
// Call emit emit method to generate new particles.
//
{
MStatus status;
// Determine if we are requesting the output plug for this emitter node.
//
if( !(plug == mOutput) )
return( MS::kUnknownParameter );
// Get the logical index of the element this plug refers to,
// because the node can be emitting particles into more
// than one particle shape.
//
int multiIndex = plug.logicalIndex( &status );
McheckErr(status, "ERROR in plug.logicalIndex.\n");
// Get output data arrays (position, velocity, or parentId)
// that the particle shape is holding from the previous frame.
//
MArrayDataHandle hOutArray = block.outputArrayValue(mOutput, &status);
McheckErr(status, "ERROR in hOutArray = block.outputArrayValue.\n");
// Create a builder to aid in the array construction efficiently.
//
MArrayDataBuilder bOutArray = hOutArray.builder( &status );
McheckErr(status, "ERROR in bOutArray = hOutArray.builder.\n");
// Get the appropriate data array that is being currently evaluated.
//
MDataHandle hOut = bOutArray.addElement(multiIndex, &status);
McheckErr(status, "ERROR in hOut = bOutArray.addElement.\n");
// Get the data and apply the function set.
//
MFnArrayAttrsData fnOutput;
MObject dOutput = fnOutput.create ( &status );
McheckErr(status, "ERROR in fnOutput.create.\n");
// Check if the particle object has reached it's maximum,
// hence is full. If it is full then just return with zero particles.
//
bool beenFull = isFullValue( multiIndex, block );
if( beenFull )
{
return( MS::kSuccess );
}
// Get deltaTime, currentTime and startTime.
// If deltaTime <= 0.0, or currentTime <= startTime,
// do not emit new pariticles and return.
//
MTime cT = currentTimeValue( block );
MTime sT = startTimeValue( multiIndex, block );
MTime dT = deltaTimeValue( multiIndex, block );
if( (cT <= sT) || (dT <= 0.0) )
{
// We do not emit particles before the start time,
// and do not emit particles when moving backwards in time.
//
// This code is necessary primarily the first time to
// establish the new data arrays allocated, and since we have
// already set the data array to length zero it does
// not generate any new particles.
//
hOut.set( dOutput );
block.setClean( plug );
return( MS::kSuccess );
}
// Get speed, direction vector, and inheritFactor attributes.
//
double speed = speedValue( block );
MVector dirV = directionVector( block );
double inheritFactor = inheritFactorValue( multiIndex, block );
// Get the position and velocity arrays to append new particle data.
//
MVectorArray fnOutPos = fnOutput.vectorArray("position", &status);
MVectorArray fnOutVel = fnOutput.vectorArray("velocity", &status);
// Convert deltaTime into seconds.
//
double dt = dT.as( MTime::kSeconds );
// Apply rotation to the direction vector
MVector rotatedV = useRotation ( dirV );
// position,
MVectorArray inPosAry;
// velocity
MVectorArray inVelAry;
// emission rate
MIntArray emitCountPP;
// Get the swept geometry data
//
MObject thisObj = this->thisMObject();
MPlug sweptPlug( thisObj, mSweptGeometry );
if ( sweptPlug.isConnected() )
{
MDataHandle sweptHandle = block.inputValue( mSweptGeometry );
// MObject sweptData = sweptHandle.asSweptGeometry();
MObject sweptData = sweptHandle.data();
MFnDynSweptGeometryData fnSweptData( sweptData );
// Curve emission
//
if (fnSweptData.lineCount() > 0) {
int numLines = fnSweptData.lineCount();
for ( int i=0; i<numLines; i++ )
{
inPosAry.clear();
inVelAry.clear();
emitCountPP.clear();
MDynSweptLine line = fnSweptData.sweptLine( i );
// ... process current line ...
MVector p1 = line.vertex( 0 );
MVector p2 = line.vertex( 1 );
inPosAry.append( p1 );
inPosAry.append( p2 );
inVelAry.append( MVector( 0,0,0 ) );
inVelAry.append( MVector( 0,0,0 ) );
// emit Rate for two points on line
emitCountPP.clear();
status = emitCountPerPoint( plug, block, 2, emitCountPP );
emit( inPosAry, inVelAry, emitCountPP,
dt, speed, inheritFactor, rotatedV, fnOutPos, fnOutVel );
}
}
// Surface emission (nurb or polygon)
//
if (fnSweptData.triangleCount() > 0) {
int numTriangles = fnSweptData.triangleCount();
for ( int i=0; i<numTriangles; i++ )
{
inPosAry.clear();
inVelAry.clear();
emitCountPP.clear();
MDynSweptTriangle tri = fnSweptData.sweptTriangle( i );
// ... process current triangle ...
MVector p1 = tri.vertex( 0 );
MVector p2 = tri.vertex( 1 );
MVector p3 = tri.vertex( 2 );
MVector center = p1 + p2 + p3;
center /= 3.0;
inPosAry.append( center );
inVelAry.append( MVector( 0,0,0 ) );
// emit Rate for two points on line
emitCountPP.clear();
status = emitCountPerPoint( plug, block, 1, emitCountPP );
emit( inPosAry, inVelAry, emitCountPP,
dt, speed, inheritFactor, rotatedV, fnOutPos, fnOutVel );
}
}
}
// Update the data block with new dOutput and set plug clean.
//
hOut.set( dOutput );
block.setClean( plug );
return( MS::kSuccess );
}