Color Quantities

Visualize color data at the nodes or cells of a sparse volume grid.

Example: adding color quantities to a sparse volume grid

import polyscope as ps
import numpy as np

ps.init()

origin = (0., 0., 0.)
cell_width = (0.1, 0.1, 0.1)

occupied_cells = np.array([
    [0, 0, 0], [1, 0, 0], [0, 1, 0], [1, 1, 0],
])

ps_grid = ps.register_sparse_volume_grid("sample sparse grid", origin, cell_width, occupied_cells)

# === Cell color: one RGB color per occupied cell ===
cell_colors = np.array([
    [1., 0., 0.], [0., 1., 0.], [0., 0., 1.], [1., 1., 0.],
])
ps_grid.add_color_quantity("cell color", cell_colors, defined_on='cells', enabled=True)

# === Node color: colors at node indices ===
node_set = set()
for cell in occupied_cells:
    for dx in range(2):
        for dy in range(2):
            for dz in range(2):
                node_set.add((cell[0]+dx, cell[1]+dy, cell[2]+dz))
node_indices = np.array(list(node_set), dtype=np.int32)
node_colors = np.random.rand(len(node_indices), 3).astype(np.float32)

ps_grid.add_color_quantity("node color", node_colors, defined_on='nodes',
                           node_indices=node_indices, enabled=True)

ps.show()

Add cell colors

SparseVolumeGrid.add_color_quantity(name, colors, defined_on='cells', **color_args)

Add a color quantity defined at the cells of the grid.

• name string, a name for the quantity
• colors an (N, 3) numpy array of RGB colors in [0, 1], one per occupied cell in the same order as the occupied_cells array used at registration
• defined_on string, must be 'cells'

This function also accepts optional keyword arguments listed below, which customize the appearance and behavior of the quantity.

Add node colors

SparseVolumeGrid.add_color_quantity(name, colors, defined_on='nodes', node_indices=..., **color_args)

Add a color quantity defined at the nodes of the grid.

Node colors are passed as paired arrays of node indices and colors. For a cell with grid indices (i, j, k), its corner nodes have indices (i+dx, j+dy, k+dz) for dx, dy, dz in {0, 1}. The node indices may be passed in any order, and extra entries (for nodes not required by any occupied cell) are ignored. However, all required node values must be present.

• name string, a name for the quantity
• colors an (N, 3) numpy array of RGB colors in [0, 1], one per node
• defined_on string, must be 'nodes'
• node_indices an (N, 3) integer numpy array of node grid indices, required when defined_on='nodes'

This function also accepts optional keyword arguments listed below, which customize the appearance and behavior of the quantity.