removed colorscale attribute from mesh3d

[VeraZab]

that attribute shouldn't exist for that trace

[etpinard]

Looks like a lot code downstream of mesh3d/attributes.jsrelies on colorscale. For example,

• in default.js here
• convert.js here

causing a few image tests to fail.

But, looks like gl-mesh3d does handle color maps here. Maybe we just got lazy and never added a test and docs for them?

@VeraZab this block here suggest that colorscale is used only when the mesh3d trace intensity is set. Could you confirm or infirm. Thanks!

[mdtusz]

@VeraZab @etpinard @cldougl

We'll want to update the docs to be much more clear regarding colorscale on meshes like this.

To clarify

colorscale only has an effect if intensity is set as well for the surface, where intensity is an array of normalized values for each vertex of the mesh corresponding to an interpolated color value based on the colorscale. E.g in extreme pseudocode (vertices isn't an actual plotly attribute).

vertices: [A, B, C]
intensity: [0, 0.5, 1]
colorscale: [[0, rgb(255, 0, 0)], [0.5, rgb(0, 255, 0)], [1, rgb(0, 0, 255)]]

This will create a surface where vertex A will be pure red, B will be green, and C will be blue, and a smooth gradient will be interpolated inbetween the vertices.

Here's a tetrahedron example on jsbin.

[etpinard]

@mdtusz ... and we should add an image test for that case too.

[etpinard]

closed in favour of #643