from cura.PickingPass import PickingPass

[Cuq 18]

Hello,

 

I'm working on a plugin and I need in this case to get the normal vector on a picked point.  Using PickingPass and getPickedPosition  returns the coordinates of the point , but is it possible to get the normal vector on this point ?

 

https://github.com/Ultimaker/Cura/blob/master/cura/PickingPass.py

 

Thanks a lot !

[rburema 16]

Not directly, but something like this can be done. It's a bit cumbersome though.

 

You can get the face-id of the face under a screen-position with SelectionPass.getFaceIdAtPosition, then work out the intended object, then get the normal from the/that mesh. (For example as happens in SelectionTool._pixelSelection)

 

As an alternative; if your plugin has it's own stage (like next to Prepare, Preview, Monitor) then I think it becomes an option to write your own RenderPass and shader to get the normal out that way.

 

[ahoeben 983]

1 hour ago, rburema said:

 if your plugin has it's own stage then I think it becomes an option to write your own RenderPass and shader

 

You don't need your own stage for that. The SupportEraser adds the picking pass to the Prepare and Preview pass, and OP's plugin could do the same. The problem though is that you can only get 8 bit RGBA values from the pass. Pickingpass uses a shader to encode a 24 bit "greyscale" value in the 3 R,G and B bytes. But for a normal vector, you would really want to have 3 16 bit floats. You could try to encode floats in ints, but you would still need 3 of them, and with a single renderpass you only get 4*8=32 bit maximum.

 

My still-in-development measuring plugin creates 3 passes to get a more accurate position than what the pickingpass affords. Perhaps OP can have another look there: https://github.com/fieldOfView/Cura-MeasureTool/

 

[ahoeben 983]

Alternatively, you could look into using the picking that is provided by Trimesh:

https://trimsh.org/trimesh.ray.ray_triangle.html