watertight-ray-triangle-intersection

An implementation of the Watertight Ray/Triangle Intersection algorithm

Background / Initial Motivation

I've been using substack/ray-triangle-intersection for some of my mouse picking, but Möller–Trumbore ray-triangle intersection algorithm that it uses does not satisfy my use case this time around.

I'm mousing over a grid based terrain and determining which tile in the terrain is moused over. Since the Möller–Trumbore algorithm isn't watertight, when I mouse in between two tiles neither tile is selected and thus it's as if you aren't mousing over the terrain at all.

The goal of this watertight-ray-triangle-intersection module is to implement the algorithm found in the Water Ray/Triangle Intersection in order to solve this problem for myself, and hopefully you too.

To Install

$ npm install --save watertight-ray-triangle-intersection

Usage

var rayTriIntersect = require('watertight-ray-triangle-intersection')
 
var rayOrigin = [3, 4, 0.1]
var ray = [-3, -4, -0.1]
var triangle = [
  [-10, 0, 10],
  [10, 0, 10],
  [0, 0, -10]
]
 
var intersection = []
 
rayTriIntersect(intersection, rayOrigin, ray, triangle)
console.log(intersection)
// [0, 0, 0]

API

intersection(intersectionCoords, rayOrigin, ray, triangle, options) -> intersectionCoords

intersectionCoords

Required

Type: Array[3]

rayOrigin

Required

Type: Array[3]

The start location of your ray

var rayOrigin = [500, 25, 17]

ray

Required

Type: Array[3]

// Example ray
var ray = [1, 0, 0]

A vector that specifies your ray's direction in 3d space.

triangle

Required

Type: Array[3]

An array of 3 arrays.

Each of the sub arrays is an array of 3 points.

// Example Triangle
var triangle = [
  [-1, 0, 1],
  [1, 0, 1],
  [0, 0, -1]
]

options

var options = {
  backfaceCulling: false
}

backfaceCulling

Type: Boolean

Default: false

Whether or not to use back-face culling when testing for intersections.

TODO:

• benchmark
• fix divide by zero issues when a ray had a 0 as x, y, or z (see code comments for further details)

References

• Watertight Ray/Triangle Intersection

License

MIT