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## Triangle/Ray Intersection

version 1.5 (211 KB) by

Fast vectorized triangle/ray intersection algorithm

Updated

Ray/triangle intersection using the algorithm proposed by Möller and
Trumbore (1997), implemented as highly vectorized MATLAB code.
The algorithm can work with one and two sided surfaces, as well as, with
infinite lines, rays (lines bounded on one side) and segments (lines bounded on
both sides).
Input (all arrays in in Nx3, where N is number of vertices or rays):
orig : ray's origin
dir : ray's direction
vert0, vert1, vert2: vertices of the triangle
Output:
Intersect - boolean array of length N
t - distance from the ray origin to the intersection point in |dir|
u,v - barycentric coordinates of the intersection point units
xcoor - carthesian coordinates of the intersection point

In addition PointInsideVolume is 3D equivalent to 2D inpolygon function and can test if
array of points is inside or outside any volume defined by the surface grid.

Igor

### Igor (view profile)

To do your program better I suggests
1) Add description about use option FullReturn. It shold be '1' but not 'true' for example.
2) Add in initialize default output string
xcoor=zeros(size(orig));
If xcoor not initialized than if no intersections error appear with params count.

Jamie Heather

### Jamie Heather (view profile)

Nice vectorised implementation with handy options for choosing between ray/line/segments and handling numerical precision issues - thanks!

Jaroslaw Tuszynski

### Jaroslaw Tuszynski (view profile)

Reply to Murat: You might have to look into using "border" parameter. If it does not work can you construct a scenario that demonstrates the issue and email it to me

Murat

### Murat (view profile)

Hi, the code is working well but it sometimes cannot handle with large incident angles. When the incident angle is around 90, it ignores triangles. Could you correct it?

Ehsan golk

Jeffrey

### Jeffrey (view profile)

I'm having trouble with the many rays, many faces option. Lets say I have 11 faces and 5 rays. What resizing of the inputs needs to be done? Do I need to repmat all arrays to be of size 55x3?

Based on what I can tell it can handle:
- one ray, many faces
- many rays, one face
- many rays, many faces (but # of faces = # of rays)

But I think I am just missing something here.

Jaroslaw Tuszynski

### Jaroslaw Tuszynski (view profile)

Reply to Nick: In many rays and many triangle case you still test for intersection of prearranged pairs and the return value informs you which ray/triangle pair intersected

Nick

### Nick (view profile)

Very useful but when considering many rays and many triangles is there a way to find which ray has intersected which triangle?

Nick

Amilcar Torres

Ben

### Ben (view profile)

Looks great. Downloaded and will try it later.

Jaroslaw Tuszynski

### Jaroslaw Tuszynski (view profile)

Re to Anton Semechko: This is a low level function which can be called with one ray and many faces, many faces and one ray or many faces and rays. It is quite simple to apply repmat function to the inputs.

Anton Semechko

### Anton Semechko (view profile)

why does the number of rays have to equal the number of faces? that's so inconvenient

 15 Jun 2016 1.5 correct description: no symbolic toolbox is needed 3 Oct 2014 1.5 Major rewrite of the function with additional options and output variables. Also provided PointInsideVolume function 7 Jun 2013 1.4 documentation improvements and typo correction 21 Mar 2013 1.2 correct treatment of 3x3 arrays as suggested by Andreas Weber 7 Oct 2011 1.1 Improvements to border handling
##### MATLAB Release
MATLAB 7.12 (R2011a)
##### Acknowledgements

Inspired by: Ray/Triangle Intersection

Inspired: RayShapeArticle_FEX.zip, in_polyhedron

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