calc_line_triangle_intersect - jaybgager/tracertools GitHub Wiki

Calculates the intersection point of a line segment and a triangular plane if one exists. Primarily a utility function used by several others.

Arguments:

  • line ((2,3)-shape numpy array of floats, mandatory)
    • the point coords of the line segment's ends
    • e.g. [1.0, 2.0, 3.0], [4.0, 5.0, 6.0](/jaybgager/tracertools/wiki/1.0,-2.0,-3.0],-[4.0,-5.0,-6.0)
  • triangle ((3,3)-shape numpy array of floats, mandatory)
    • the point coords of the triangle's vertices
    • e.g.[1.0, 2.0, 3.0], [4.0 ,5.0, 6.0], [7.0, 8.0, 9.0](/jaybgager/tracertools/wiki/1.0,-2.0,-3.0],-[4.0-,5.0,-6.0],-[7.0,-8.0,-9.0)
  • precision (integer, optional, default=0)
    • maximum number of decimal points to include when calculating intersection points
    • default of 0 rounds to nearest integer as this is fine for most neuroglancer uses

Returns:

  • result (varies, see description)
    • returns a (3)-shape numpy array of floats if an intersection is found, otherwise returns None value

Examples

Default Usage

INPUT:

import tracertools as tt
import numpy as np

intersect = tt.calc_line_triangle_intersect(
    line = np.array(
        [
            [0,0,0],
            [1,2,3]
        ]
    ),
    triangle = np.array(
        [
            [2,0,0],
            [0,3,0],
            [0,0,4]
        ]
    ),
)

print(intersect)

OUTPUT:

[1.,1.,2.]

High Precision

INPUT:

import tracertools as tt
import numpy as np

intersect = tt.calc_line_triangle_intersect(
    line = np.array(
        [
            [0,0,0],
            [1,2,3]
        ]
    ),
    triangle = np.array(
        [
            [2,0,0],
            [0,3,0],
            [0,0,4]
        ]
    ),
    precision = 3,
)

print(intersect)

OUTPUT:

[0.522 1.043 1.565]

[!NOTE] Using high precision (e.g 16+ digits) with small coord values (e.g. [1,1,1]) can result in false negative results, as the float math involved sometimes produces very tiny discrepancies when checking results.