How to calculate polygon intersections?

Suppose I have a box and another box that has been shrunk in two dimensions and elongated in the third. The stretched box then intersects the first box, requiring some additional consideration for rendering.

It would be cool to support intersections like these if it's not already possible.

import numpy, svg3d, pyrr, math

def get_box_faces(sx, sy, sz):

    verts = numpy.float32(
        [(-1, -1, -1), (-1, -1, 1), (1, -1, 1), (1, -1, -1),
         (-1,  1, -1), (-1,  1, 1), (1,  1, 1), (1,  1, -1),
        ])

    faces = numpy.int32([
        (0, 1, 2, 3),
        (4, 5, 6, 7),
        (0, 1, 5, 4),
        (1, 2, 6, 5),
        (2, 3, 7, 6),
        (3, 0, 4, 7)
        ])

    return 0.5*numpy.float32([sx, sy, sz])*(verts[faces])

def generate_svg(filename):
    view = pyrr.matrix44.create_look_at(
        eye=[50, 40, 120], target=[0, 0, 0], up=[0, 1, 0]
    )
    projection = pyrr.matrix44.create_perspective_projection(
        fovy=15, aspect=1, near=10, far=200
    )
    camera = svg3d.Camera(view, projection)

    style = dict(
        fill="white",
        fill_opacity="0.75",
        stroke="black",
        stroke_linejoin="round",
        stroke_width="0.005",
    )

    faces = numpy.concatenate(
        [get_box_faces(4, 4, 60), get_box_faces(14, 14, 14)]
        )
    print(faces.shape)
    mesh = svg3d.Mesh(faces, style=style)
    view = svg3d.View(camera, svg3d.Scene([mesh]))
    svg3d.Engine([view]).render(filename)

generate_svg("boxes.svg")

prideout / svg3d

How to calculate polygon intersections? #3