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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
Download Patch File Download Diff File Expand all files Collapse all files

4
source/blender/blenlib/BLI_math_geom.h
View File

@@ -109,9 +109,9 @@ float dist_signed_squared_to_corner_v3v3v3(
const float p[3],
const float v1[3], const float v2[3], const float v3[3],
const float axis_ref[3]);
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 dist_squared_ray_to_seg_v3(
const float ray_origin[3], const float ray_direction[3],
const float v0[3], const float v1[3],

23
source/blender/blenlib/intern/math_geom.c
View File

@@ -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);
}

30
source/blender/editors/mesh/editmesh_select.c
View File

@@ -1153,16 +1153,13 @@ bool EDBM_unified_findnearest_from_raycast(
if ((BM_elem_flag_test(e, BM_ELEM_HIDDEN) == false) &&
(BM_edge_is_boundary(e)))
{
float depth;
if (use_vert) {
for (uint j = 0; j < 2; j++) {
BMVert *v = *((&e->v1) + j);
float point[3];
mul_v3_m4v3(point, obedit->obmat, coords ? coords[BM_elem_index_get(v)] : v->co);
const float dist_sq_test = dist_squared_to_ray_v3(
ray_origin, ray_direction,
point, &depth);
const float dist_sq_test = dist_squared_to_ray_v3_normalized(
ray_origin, ray_direction, point);
if (dist_sq_test < dist_sq_best) {
dist_sq_best = dist_sq_test;
best.base_index = base_index;
@@ -1186,9 +1183,8 @@ bool EDBM_unified_findnearest_from_raycast(
mid_v3_v3v3(point, e->v1->co, e->v2->co);
}
mul_m4_v3(obedit->obmat, point);
const float dist_sq_test = dist_squared_to_ray_v3(
ray_origin, ray_direction,
point, &depth);
const float dist_sq_test = dist_squared_to_ray_v3_normalized(
ray_origin, ray_direction, point);
if (dist_sq_test < dist_sq_best) {
dist_sq_best = dist_sq_test;
best.base_index = base_index;
@@ -1208,10 +1204,8 @@ bool EDBM_unified_findnearest_from_raycast(
if (BM_elem_flag_test(v, BM_ELEM_HIDDEN) == false) {
float point[3];
mul_v3_m4v3(point, obedit->obmat, v->co);
float depth;
const float dist_sq_test = dist_squared_to_ray_v3(
ray_origin, ray_direction,
v->co, &depth);
const float dist_sq_test = dist_squared_to_ray_v3_normalized(
ray_origin, ray_direction, v->co);
if (dist_sq_test < dist_sq_best) {
dist_sq_best = dist_sq_test;
best.base_index = base_index;
@@ -1233,10 +1227,8 @@ bool EDBM_unified_findnearest_from_raycast(
mid_v3_v3v3(point, e->v1->co, e->v2->co);
}
mul_m4_v3(obedit->obmat, point);
float depth;
const float dist_sq_test = dist_squared_to_ray_v3(
ray_origin, ray_direction,
point, &depth);
const float dist_sq_test = dist_squared_to_ray_v3_normalized(
ray_origin, ray_direction, point);
if (dist_sq_test < dist_sq_best) {
dist_sq_best = dist_sq_test;
best.base_index = base_index;
@@ -1260,10 +1252,8 @@ bool EDBM_unified_findnearest_from_raycast(
BM_face_calc_center_median(f, point);
}
mul_m4_v3(obedit->obmat, point);
float depth;
const float dist_sq_test = dist_squared_to_ray_v3(
ray_origin, ray_direction,
point, &depth);
const float dist_sq_test = dist_squared_to_ray_v3_normalized(
ray_origin, ray_direction, point);
if (dist_sq_test < dist_sq_best) {
dist_sq_best = dist_sq_test;
best.base_index = base_index;