How to use CSV data to color 1 million voxels staked in a Rubik's Cube like model?

Question

The cube is composed of 1 million voxels (100x100x100) having the same size (1 unit). Voxel information is saved in this .txt file having the format: (4 columns x 1 million lines).

The first 3 columns represent x, y, z of each voxel, while the 4^th column has the values: {0, 1, 2, 7, 8, 9, 10, 12, 13, 16, 17}. Each number represents a color in the model (eg: {black, yellow, green, blue, cyan, lawngreen, pink, magenta, white, gray, orange})

Because of the high number of voxels, I tried to pass by creating instances by adapting a code that I found here. the script worked for representing all voxels as instances. However, I'm unable to find a solution to color each voxel based on data in the 4^th column within the voxels file.

I tried to use instancing and arrays by geometry nodes but it is still challenging for me as it's just my 2^nd application using Blender.

Here is the script representing the voxels:

import bpy
import numpy as np
import mathutils as mt
bpy.ops.object.select_all(action="SELECT")
bpy.ops.object.delete()
C = bpy.context
#open text file
rawfile = open("/Users/test/Documents/voxels.txt","r")
data=np.loadtxt( rawfile, delimiter=' ' )
rawfile.close()
#Create and arrange mesh data
verts = [ mt.Vector( data[i,:3] ) for i in range(data.shape[0]) ]
m = bpy.data.meshes.new('pc')
m.from_pydata(verts, [], [])
Create mesh object and link to scene collection
o = bpy.data.objects.new('pc', m)
C.scene.collection.objects.link( o )
#Add primitive cube
bpy.ops.mesh.primitive_cube_add( size = 1)
isobj = bpy.data.objects[C.object.name]
Set instancing props
for ob in [ isobj, o]:
    ob.instance_type = 'VERTS'
    ob.show_instancer_for_viewport = True
    ob.show_instancer_for_render = True
Set instance parenting (parent cube to verts)
o.select_set(True)
C.view_layer.objects.active = o
bpy.ops.object.parent_set( type = 'VERTEX', keep_transform = True )

Answer 1

I'm unsure about storing colors for individual instances. But latest blender comes with point cloud feature for cycles, so you can try that way also.

Here the script create vertices and stores color attribute. The vertices are then converted to point cloud using geometry nodes.

import bpy
import numpy as np
import mathutils as mt
bpy.ops.object.select_all(action="SELECT")
bpy.ops.object.delete()
C = bpy.context
#open text file
rawfile = open("/home/hari/Desktop/voxels.txt","r")
data=np.loadtxt( rawfile, delimiter=' ' )
rawfile.close()
color dict
colordict = {0:[0.000000, 0.000000, 0.000000, 1.000000],
             1:[1.000000, 1.000000, 0.000000, 1.000000],
             2:[0.000000, 1.000000, 0.000000, 1.000000],
             7:[0.000000, 0.000000, 1.000000, 1.000000],
             8:[0.000000, 0.750000, 1.000000, 1.000000],
             9:[0.929871, 0.302988, 0.571237, 1.000000],
             10:[1.000000, 0.527115, 0.597202, 1.000000],
             12:[1.000000, 0.000000, 1.000000, 1.000000],
             13:[1.000000, 1.000000, 1.000000, 1.000000],
             16:[0.500000, 0.500000, 0.500000, 1.000000],
             17:[1.000000, 0.250000, 0.000000, 1.000000]}
#Create and arrange mesh data
verts = [ mt.Vector( data[i,:3] ) for i in range(data.shape[0]) ]
create voxel object
obj_name = "Voxels"
mesh_data = bpy.data.meshes.new(obj_name + "_data")
obj = bpy.data.objects.new(obj_name, mesh_data)
bpy.context.scene.collection.objects.link(obj)
mesh_data.from_pydata(verts, [], [])
store color attribute
colors = np.array([colordict.get(i,[0,0,0,1]) for i in data[:,-1]]).ravel()

obj.data.attributes.new(name='col', type='FLOAT_COLOR', domain='POINT')
obj.data.attributes['col'].data.foreach_set('color', colors)

Instancing cubes on points