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add_mesh per-face coloring #984

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cbf57c7
add_mesh per-face coloring
sp-droid Jan 30, 2026
6a56506
Clarify color parameter description in mesh.py
sp-droid Feb 6, 2026
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27 changes: 16 additions & 11 deletions fastplotlib/graphics/mesh.py
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Original file line number Diff line number Diff line change
Expand Up @@ -50,20 +50,19 @@ def __init__(
The 3D positions of the vertices.

indices: array-like
The indices into the positions that make up the triangles. Each 3
subsequent indices form a triangle.
The indices into the positions that make up the triangles (3 indices per row) or quads (4 indices per row). Each row is a face.

mode: one of "basic", "phong", "slice", default "phong"
* basic: illuminate mesh with only ambient lighting
* phong: phong lighting model, good for most use cases, see https://en.wikipedia.org/wiki/Phong_shading
* slice: display a slice of the mesh at the specified ``plane``

plane: (float, float, float, float), default (0., 0., 1., 0.)
Slice mesh at this plane. Sets (a, b, c, d) in the equation the defines a plane: ax + by + cz + d = 0.
Used only if `mode` = "slice". The plane is defined in world space.

colors: str, array, or iterable, default "w"
A uniform color, or the per-position colors.
A uniform color (name or linear-RGBA tuple), per-vertex colors (length=positions), or per-face colors (length=indices). The introduced color is assumed to be in linear RGB scale. Popular colormaps such as the ones from matplotlib give it in sRGB. Careful!

mapcoords: array-like
The per-position coordinates to which to apply the colormap (a.k.a. texcoords).
Expand Down Expand Up @@ -120,7 +119,7 @@ def __init__(
self._clim = clim

uniform_color = "w"
per_vertex_colors = False
non_uniform_colors = False

if cmap is None:
if colors is None:
Expand All @@ -130,14 +129,15 @@ def __init__(
uniform_color = colors
self._colors = UniformColor(uniform_color)
elif isinstance(colors, VertexColors):
per_vertex_colors = True
non_uniform_colors = True
self._colors = colors
else:
per_vertex_colors = True
non_uniform_colors = True
self._colors = VertexColors(
colors, n_colors=self._positions.value.shape[0]
colors, n_colors=len(colors)
)


geometry = pygfx.Geometry(
positions=self._positions.buffer, indices=self._indices._buffer
)
Expand All @@ -164,7 +164,7 @@ def __init__(
)

# Set all the data
if per_vertex_colors:
if non_uniform_colors:
geometry.colors = self._colors.buffer
if self._mapcoords is not None:
geometry.texcoords = self._mapcoords
Expand All @@ -179,8 +179,13 @@ def __init__(
# face_map = None #: Use per-face texture coords (``geometry.texcoords``), and sample these in ``material.map``.
if mapcoords is not None and cmap is not None:
material.color_mode = "vertex_map"
elif per_vertex_colors:
material.color_mode = "vertex"
elif non_uniform_colors:
if self._colors.value.shape[0] == self._indices.value.shape[0]:
material.color_mode = "face"
elif self._colors.value.shape[0] == self._positions.value.shape[0]:
material.color_mode = "vertex"
else:
raise ValueError("colors length does not match number of vertices or faces")
else:
material.color_mode = "uniform"

Expand Down