issue about SurfacePlotVisual

[JintaoLee-Roger]

Hi!

When I use SurfacePlot to draw a surface and seed color parameter, an error occurs:

File "/opt/homebrew/Caskroom/miniforge/base/lib/python3.10/site-packages/vispy/visuals/surface_plot.py", line 129, in _prepare_mesh_colors
    colors = colors.reshape(num_vertices, 3)
ValueError: cannot reshape array of size 960000 into shape (240000,3)

I note that the _prepare_mesh_colors function in vispy/visuals/surface_plot.py is:

    def _prepare_mesh_colors(self, colors):
        if colors is None:
            return
        colors = np.asarray(colors)
        if colors.ndim == 3:
            # convert (width, height, 4) to (num_verts, 4)
            vert_shape = self.__vertices.shape
            num_vertices = vert_shape[0] * vert_shape[1]
            colors = colors.reshape(num_vertices, 3)
        return colors

The comment and document state that I should pass in a matrix of dimensions (width, height, 4), which will then be transformed into a matrix of dimensions (num_verts, 4). However, the code does not follow this approach; instead, it transforms it into a matrix of dimensions (num_verts, 3).

[djhoese]

At first glance this does seem like a bug, but also what colors are you providing? RGB? RGBA?

Skimming through the code it does definitely seem like RGBA (4 elements) is the more performant way of providing the colors. Otherwise, VisPy adds the alpha channel itself which requires a copy of the color array. I'm not really sure how or why this is reshaping to 3 (RGB). If you feel up to it, it would be great if you could make a pull request fixing this.

[djhoese]

Related #2542