Volume on non-uniform grid does not appear

Plotting a 3D volume with a non-uniform grid yields a blank canvas with only the axes and the side bar.

Non-uniform means that the x, y, and z parameters are not simply obtained from a call to mgrid. For my application, they correspond to an affine transformation of such a regular grid, exactly like in https://community.plotly.com/t/3d-volume-plotting-with-non-orthogonal-grid/51662. There is also a StackOverflow answer pointing to this problem: https://stackoverflow.com/questions/66141821/plotting-a-3d-volume-plot-in-r-using-discrete-3d-points#answers.

This is either a bug or simply a documentation mistake, since the reference explicitly states that the coordinates should come from a "uniform or non-uniform 3-D grid" (see https://plotly.com/javascript/reference/volume/#volume).

Reproducer: https://codepen.io/Liozou/pen/OJaQMzK. On the left, the expected behavior, working on a uniform grid. On the right, the issue, on an affine-transformed grid. Black dots are used to visualize the grid itself.

Inizia con il riproduttore CodePen collegato e confronta i casi di griglia uniforme e trasformazione affine nella traccia del volume. Leggi il riferimento del volume, in particolare i relativi requisiti sulle coordinate, quindi segui il punto di ingresso del rendering del volume per identificare perché la griglia non uniforme produce un canvas vuoto. Il lavoro è completato quando il volume trasformato affine viene renderizzato, mantenendo intatto il comportamento esistente della griglia uniforme.