DXF composed of Face3d entities to regular grid

[antoinecollet5]

Hi !

What I am trying to achieve:

I have a dxf composed of around 70k Face3D entities. These represent volumes. I can load it with libs such as ezdxf without problem.

Now I have a regular grid (sugarbox kind with Parallelepiped grid cells) which is referenced in the same space (basically a numpy array). What I want to achieve is to iterate over the Face3D and compute the intersection with the grid. Basically, I would like to compute for each grid cell the proportion of coverage by these volumes.

I know how to do that in 2d using libs like shapely, but what would be the right tool for such a task in 3D ? Can CQ helps here ?

Thank you in advance for the help.

[jmwright]

I do not think that CadQuery's DXF import is capable of handling Face3D entities as-is, but you could integrate your ezdxf solution as a plugin since ezdxf is already a dependency of CadQuery.

The other devs will have ideas, but here are some initial thoughts.

• You can get the bounding box of shapes and use that to find intersections. This only works well for simple planar shapes like rectangular prisms. For instance, the bounding box of a sphere is a cube, which does not give you an accurate representation of intersection of the sphere with another shape.
• You might be able to use the newer closest method to check the closest point between two shapes.
• You can also use boolean options like intersect and then check the volume that is left over. However, boolean operation performance is not great with OpenCASCADE since it is a Brep kernel, and doing 70k checks this way will probably take a long time.
• I also believe there is a method for checking intersection at the OpenCASCADE level, but I cannot remember what it is and do not think it is exposed in the CadQuery API layers yet.