Point Cloud « Samiam’s Scribble Pad

October 14, 2010

Point Cloud in Nuke using “PositionToPoints”, 3delight Rendman Shader Language and cortex-vfx

Filed under: Uncategorized — Tags: Bake, cortex-vfx, Nuke, Point Cloud, Renderman — admin @ 1:51 pm

Here is the end result:

Nuke Node "PositionToPoints" with 3d EXR inputs

First things first I need a model to work with

Model

Stanford Bunny OBJ via MD Fischer

Shader

surface bakeColourAndPosition(
uniform float diffuseAmount = 1;
varying color surfaceColour = color(0.18,0.18,0.18);
varying color opacityColour = color(0.99,0.99,0.99);
uniform string bakeFile="/tmp/out.bake";
)
{
   varying normal Nn = normalize(N);
   Ci = diffuse(Nn)*surfaceColour*diffuseAmount*Cs;
   Oi = opacityColour*Os;
   varying point Pworld = transform("current","world",P);
   bake(concat(bakeFile,"Position"),s,t,Pworld);
   bake(concat(bakeFile,"Colour"),s,t,Ci);
   Ci *= Oi;
}

This shader will produce two text “bakefile” files in the /tmp directory

Note: The texture coordinates are ignored, only using the 3rd,4th and 5th values

one named out.bakeColour with colour information
one named out.bakePosition with position information

Output Bakefiles

Download .tar.gz here…

Due to the SIMD nature of shaders the line count of each of the bake files is the same so they should contain line for line the same information about the Position and Colour Respectively.

They are in ASCII format so they are easy enough to parse with Python.

here is an example of thier content:

out.bakePositionmh
3
0 1 -0.07415867 0.17987273 -0.05079475
0 1 -0.073529155 0.1800126 -0.051191031
0 1 -0.07289961 0.18015243 -0.051587344
0 1 -0.072270096 0.18029229 -0.051983685
0 1 -0.07164058 0.18043211 -0.052379965
0 1 -0.07101102 0.18057197 -0.052776248
0 1 -0.07038155 0.1807118 -0.053172619

Creating Position and Colour EXR files using cortex-vfx

#!/usr/bin/env python
 
import sys,os,math
 
IECoreInstallPath = "/usr/lib/python2.6/site-packages"
 
if IECoreInstallPath not in sys.path:
	sys.path.append(IECoreInstallPath)
 
from IECore import *
 
bakeFolder = "/tmp"
 
colorBakeFileLocation = os.path.sep.join([bakeFolder,"out.bakeColour"])
 
positionBakeFileLocation = os.path.sep.join([bakeFolder,"out.bakePosition"])
 
 
 
 
def parseBakeFile(bakeFileLocation):
	data = []
	counter = 0
	bakeFile = open(bakeFileLocation,"r")
	for line in bakeFile.readlines():
		counter +=1
		if counter > 2:
			stuff = line.strip().split(" ")
			if len(stuff) > 2:
				data.append((float(stuff[2]),float(stuff[3]),float(stuff[4])))
	print "Completed parsing %d lines of file %s" % (len(data),bakeFileLocation)
	bakeFile.close()
	return data
 
colourData = parseBakeFile(colorBakeFileLocation)
 
positionData = parseBakeFile(positionBakeFileLocation)
 
if len(colourData) == len(positionData):
	squareSize = int(math.sqrt(len(positionData))) +1
	print "Square Size: %d, Excess Pixels : %d" % (squareSize,squareSize*squareSize - len(colourData))
	width = squareSize
	height = squareSize
	x = FloatVectorData( width * height )
	y = FloatVectorData( width * height )
	z = FloatVectorData( width * height )
 
	r = FloatVectorData( width * height )
	g = FloatVectorData( width * height )
	b = FloatVectorData( width * height )
 
	for i in range(len(colourData)):
		r[i]=colourData[i][0]
		g[i]=colourData[i][1]
		b[i]=colourData[i][2]
		x[i]=positionData[i][0]
		y[i]=positionData[i][1]
		z[i]=positionData[i][2]
 
	boxColour = Box2i( V2i( 0, 0 ), V2i( width-1, height-1 ) )
	boxPosition = Box2i( V2i( 0, 0 ), V2i( width-1, height-1 ) )
 
	imageColour = ImagePrimitive( boxColour, boxColour )
	imagePosition = ImagePrimitive( boxPosition, boxPosition )
 
	imagePosition["R"]= PrimitiveVariable( PrimitiveVariable.Interpolation.Vertex, x)
	imagePosition["G"]= PrimitiveVariable( PrimitiveVariable.Interpolation.Vertex, y)
	imagePosition["B"]= PrimitiveVariable( PrimitiveVariable.Interpolation.Vertex, z)
 
	imageColour["R"]= PrimitiveVariable( PrimitiveVariable.Interpolation.Vertex, r)
	imageColour["G"]= PrimitiveVariable( PrimitiveVariable.Interpolation.Vertex, g)
	imageColour["B"]= PrimitiveVariable( PrimitiveVariable.Interpolation.Vertex, b)
 
	writePosition = Writer.create( imagePosition, "/tmp/outPosition.exr" )
	writeColour = Writer.create( imageColour, "/tmp/outColour.exr" )
	writePosition.write()
	writeColour.write()