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Fix T60935: More numerically stable distance to ray computation

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The old function was numerically very unstable for 2 reasons:
computing the square and then subtracting the results.

In the example in T60935 all precision was lost and it returned the distance 0
for all points.

I also removed the `depth` parameter since it wasn't used and computing
it would have made the code more complicated.

Reviewers: brecht, campbellbarton

Differential Revision: https://developer.blender.org/D4308
This commit is contained in:
Jacques Lucke
2019-02-06 11:47:46 +01:00
parent f7613cf41c
commit 6202bc82b8
3 changed files with 28 additions and 29 deletions
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23
source/blender/blenlib/intern/math_geom.c
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@@ -553,16 +553,25 @@ float dist_signed_squared_to_corner_v3v3v3(
}
/**
* return the distance squared of a point to a ray.
* Compute the squared distance of a point to a line (defined as ray).
* \param ray_origin: A point on the line.
* \param ray_direction: Normalized direction of the line.
* \param co: Point to which the distance is to be calculated.
*/
float dist_squared_to_ray_v3(
float dist_squared_to_ray_v3_normalized(
const float ray_origin[3], const float ray_direction[3],
const float co[3], float *r_depth)
const float co[3])
{
float dvec[3];
sub_v3_v3v3(dvec, co, ray_origin);
*r_depth = dot_v3v3(dvec, ray_direction);
return len_squared_v3(dvec) - SQUARE(*r_depth);
float origin_to_co[3];
sub_v3_v3v3(origin_to_co, co, ray_origin);
float origin_to_proj[3];
project_v3_v3v3_normalized(origin_to_proj, origin_to_co, ray_direction);
float co_projected_on_ray[3];
add_v3_v3v3(co_projected_on_ray, ray_origin, origin_to_proj);
return len_squared_v3v3(co, co_projected_on_ray);
}