MeshAlgo::distributePoints : Support density primvar values over 1

It's now easier to support this than not, and I don't see any good reason not to,
and we're updating the distribution a little anyway by fixing precision issues and
removing duplicates, so now seems like a good time.

Author: danieldresser-ie

src/IECoreScene/MeshAlgoDistributePoints.cpp

@@ -384,12 +384,7 @@ void distributePointsInTriangle(
 			densityInterpolation, densityView, vertexIds, faceIdx,
 			cornerDensities[0], cornerDensities[1], cornerDensities[2]
 		);
-		float maxDensity = std::max( std::max( cornerDensities[0], cornerDensities[1] ), cornerDensities[2] );
-
-		// This matches previous behaviour where a density primvar value over 1.0 does nothing, because it
-		// cannot increase the number of points generated. Maybe this is valuable as a safety mechanism?
-		// We could just delete this line, and then densities greater than 1 would work how you would expect.
-		maxDensity = std::min( 1.0f, std::max( 0.0f, maxDensity ) );
+		float maxDensity = std::max( 0.0f, std::max( std::max( cornerDensities[0], cornerDensities[1] ), cornerDensities[2] ) );
 
 		// Apply the max density from the primvar to the density passed in to PointDistribution
 		finalDensity *= maxDensity;
@@ -466,7 +461,7 @@ PointsPrimitivePtr MeshAlgo::distributePoints( const MeshPrimitive *mesh, float
 	PrimitiveVariable::IndexedView<float> densityView;
 	if( densityVar.interpolation == PrimitiveVariable::Constant )
 	{
-		density *= std::min( 1.0f, std::max( 0.0f, (IECore::runTimeCast<FloatData>(densityVar.data.get()))->readable() ) );
+		density *= std::max( 0.0f, (IECore::runTimeCast<FloatData>(densityVar.data.get()))->readable() );
 	}
 	else
 	{

test/IECoreScene/MeshAlgoDistributePointsTest.py

@@ -112,11 +112,9 @@ def pointTest( self, mesh, points, density, error=0.05, checkDuplicates = True )
 		for f in range( 0, mesh.verticesPerFace.size() ) :
 			if "density" in mesh :
 				if mesh["density"].interpolation == IECoreScene.PrimitiveVariable.Interpolation.Constant:
-					# For consistency, no primitive variable may increase the density, only decrease it.
-					# At least currently, we could just fix this now.
-					density = min( 1, mesh["density"].data.value ) * origDensity
+					density = mesh["density"].data.value * origDensity
 				else:
-					density = min( 1, mesh["density"].data[f] ) * origDensity
+					density = mesh["density"].data[f] * origDensity
 			self.assertLessEqual( abs( pointsPerFace[f] - density * mesh['faceArea'].data[f] ), density * error + len(positions) * error * error )
 
 	def testSimple( self ) :