2 * $Logfile: /Freespace2/code/Math/VecMat.h $
7 * Header file for functions that manipulate vectors and matricies
10 * Revision 1.1 2002/05/03 03:28:12 root
14 * 6 6/18/99 5:16p Dave
15 * Added real beam weapon lighting. Fixed beam weapon sounds. Added MOTD
16 * dialog to PXO screen.
18 * 5 4/28/99 11:13p Dave
19 * Temporary checkin of artillery code.
21 * 4 1/24/99 11:37p Dave
22 * First full rev of beam weapons. Very customizable. Removed some bogus
23 * Int3()'s in low level net code.
25 * 3 1/12/99 12:53a Dave
26 * More work on beam weapons - made collision detection very efficient -
27 * collide against all object types properly - made 3 movement types
28 * smooth. Put in test code to check for possible non-darkening pixels on
31 * 2 10/07/98 10:53a Dave
34 * 1 10/07/98 10:49a Dave
36 * 43 9/11/98 10:10a Andsager
37 * Optimize and rename matrix_decomp to vm_matrix_to_rot_axis_and_angle,
38 * rename quatern_rot to vm_quaternion_rotate
40 * 42 3/09/98 3:51p Mike
41 * More error checking.
43 * 41 12/17/97 5:44p Andsager
44 * Change vm_matrix_interpolate so that it does not overshoot if optional
47 * 40 9/30/97 8:03p Lawrance
48 * add missing semi-colon to function prototype
50 * 39 9/30/97 5:04p Andsager
51 * add vm_estimate_next_orientation
53 * 38 9/28/97 2:17p Andsager
54 * added vm_project_point_onto_plane
56 * 37 9/25/97 5:57p Andsager
57 * improved function description for matrix interpolate
59 * 36 9/09/97 10:15p Andsager
60 * added vm_rotate_vec_to_body() and vm_rotate_vec_to_world()
62 * 35 8/20/97 5:33p Andsager
63 * added vm_vec_projection_parallel and vm_vec_projection_onto_surface
65 * 34 8/19/97 11:42p Lawrance
66 * use atan2_safe() instead of atan2()
68 * 33 8/18/97 4:46p Hoffoss
69 * Added global default axis vector constants.
71 * 32 8/03/97 3:54p Lawrance
72 * added vm_find_bounding_sphere()
74 * 31 7/30/97 2:20p Dan
75 * from allender: fixed vm_is_vec_nan to work properly with address-of
76 * operator by adding parens around macro variables
78 * 30 7/29/97 2:48p Hoffoss
79 * Added vm_is_vec_nan().
81 * 29 7/28/97 2:21p John
82 * changed vecmat functions to not return src. Started putting in code
83 * for inline vector math. Fixed some bugs with optimizer.
85 * 28 7/28/97 3:25p Andsager
87 * 27 7/28/97 2:41p Mike
88 * Replace vm_forward_interpolate().
90 * 26 7/28/97 1:18p Andsager
91 * implement vm_fvec_matrix_interpolate(), which interpolates matrices on
94 * 25 7/24/97 5:24p Andsager
95 * implement forward vector interpolation
97 * 24 7/02/97 4:25p Mike
98 * Add matrix_interpolate(), but don't call it.
100 * 23 7/01/97 3:27p Mike
101 * Improve skill level support.
103 * 22 6/25/97 12:27p Hoffoss
104 * Added some functions I needed for Fred.
106 * 21 5/21/97 8:49a Lawrance
107 * added vm_vec_same()
109 * 20 4/15/97 4:00p Mike
110 * Intermediate checkin caused by getting other files. Working on camera
113 * 19 3/17/97 1:55p Hoffoss
114 * Added function for error checking matrices.
116 * 18 3/06/97 10:56a Mike
117 * Write error checking version of vm_vec_normalize().
118 * Fix resultant problems.
120 * 17 3/04/97 3:30p John
121 * added function to interpolate an angle.
123 * 16 2/25/97 5:12p John
124 * Added functions to see if two matrices or vectors are close.
126 * 15 2/03/97 1:30p John
127 * Put a clearer comment in for vm_vec_unrotate
129 * 14 2/03/97 1:14p John
130 * Added vm_vec_unrotate function
132 * 13 1/27/97 11:57a John
133 * added a function to rotate a point around an arbritary line.
135 * 12 11/26/96 12:18p Hoffoss
136 * Added the vm_vec_dist_squared() function.
138 * 11 11/16/96 2:38p Mike
139 * Waypoint code, under construction and a painful mess.
141 * 10 11/05/96 3:42p Mike
142 * Make AI use accuracy parameter, though not yet specified in ships.tbl
145 * Add vm_vec_rand_vec_quick.
147 * Add frand() which returns a rand in 0.0..1.0.
149 * 9 10/30/96 2:35p Mike
151 * Changed quick versions of vecmat routines to not return 1/mag. They
152 * return mag, just like non-quick versions.
154 * 8 10/24/96 10:17a Hoffoss
155 * Moved function 'compute_point_on_plane()' to vecmat.
157 * 7 10/23/96 10:32p Lawrance
158 * added function vm_vect_mag_squared()
170 //#define _INLINE_VECMAT
172 #define vm_is_vec_nan(v) (_isnan((v)->x) || _isnan((v)->y) || _isnan((v)->z))
174 //Macros/functions to fill in fields of structures
176 //macro to check if vector is zero
177 #define IS_VEC_NULL(v) (((v)->x == (float)0.0) && ((v)->y == (float)0.0) && ((v)->z == (float)0.0))
179 //macro to set a vector to zero. we could do this with an in-line assembly
180 //macro, but it's probably better to let the compiler optimize it.
181 //Note: NO RETURN VALUE
182 #define vm_vec_zero(v) (v)->x=(v)->y=(v)->z=(float)0.0
185 //macro set set a matrix to the identity. Note: NO RETURN VALUE
186 #define vm_set_identity(m) do {m->rvec.x = m->uvec.y = m->fvec.z = (float)1.0; \
187 m->rvec.y = m->rvec.z = \
188 m->uvec.x = m->uvec.z = \
189 m->fvec.x = m->fvec.y = (float)0.0;} while (0)
191 extern void vm_set_identity(matrix *m);
193 #define vm_vec_make(v,_x,_y,_z) (((v)->x=(_x), (v)->y=(_y), (v)->z=(_z)), (v))
197 extern vector vmd_zero_vector;
198 extern vector vmd_x_vector;
199 extern vector vmd_y_vector;
200 extern vector vmd_z_vector;
201 extern matrix vmd_identity_matrix;
203 //Here's a handy constant
205 #define ZERO_VECTOR {(float)0.0,(float)0.0,(float)0.0}
206 #define IDENTITY_MATRIX {(float)1.0,(float)0.0,(float)0.0, \
207 (float)0.0,(float)1.0,(float)0.0, \
208 (float)0.0,(float)0.0,(float)1.0 }
210 //fills in fields of an angle vector
211 #define vm_angvec_make(v,_p,_b,_h) (((v)->p=(_p), (v)->b=(_b), (v)->h=(_h)), (v))
214 #define vm_vec_negate(v) do {(v)->x = - (v)->x; (v)->y = - (v)->y; (v)->z = - (v)->z;} while (0);
216 typedef struct plane {
220 //Functions in library
222 //adds two vectors, fills in dest, returns ptr to dest
223 //ok for dest to equal either source, but should use vm_vec_add2() if so
224 #ifdef _INLINE_VECMAT
225 #define vm_vec_add( dst, src0, src1 ) do { \
226 (dst)->x = (src0)->x + (src1)->x; \
227 (dst)->y = (src0)->y + (src1)->y; \
228 (dst)->z = (src0)->z + (src1)->z; \
231 void vm_vec_add(vector *dest,vector *src0,vector *src1);
234 //adds src onto dest vector, returns ptr to dest
235 #ifdef _INLINE_VECMAT
236 #define vm_vec_add2( dst, src ) do { \
237 (dst)->x += (src)->x; \
238 (dst)->y += (src)->y; \
239 (dst)->z += (src)->z; \
242 void vm_vec_add2(vector *dest,vector *src);
246 //scales a vector and subs from to another
248 #ifdef _INLINE_VECMAT
249 #define vm_vec_scale_sub2( dst, src, k ) do { \
251 (dst)->x -= (src)->x*tmp_k; \
252 (dst)->y -= (src)->y*tmp_k; \
253 (dst)->z -= (src)->z*tmp_k; \
256 void vm_vec_scale_sub2(vector *dest,vector *src, float k);
259 //subs two vectors, fills in dest, returns ptr to dest
260 //ok for dest to equal either source, but should use vm_vec_sub2() if so
261 #ifdef _INLINE_VECMAT
262 #define vm_vec_sub( dst, src0, src1 ) do { \
263 (dst)->x = (src0)->x - (src1)->x; \
264 (dst)->y = (src0)->y - (src1)->y; \
265 (dst)->z = (src0)->z - (src1)->z; \
268 void vm_vec_sub(vector *dest,vector *src0,vector *src1);
272 //subs one vector from another, returns ptr to dest
273 //dest can equal source
274 #ifdef _INLINE_VECMAT
275 #define vm_vec_sub2( dst, src ) do { \
276 (dst)->x -= (src)->x; \
277 (dst)->y -= (src)->y; \
278 (dst)->z -= (src)->z; \
281 void vm_vec_sub2(vector *dest,vector *src);
285 //averages two vectors. returns ptr to dest
286 //dest can equal either source
287 vector *vm_vec_avg(vector *dest,vector *src0,vector *src1);
289 //averages four vectors. returns ptr to dest
290 //dest can equal any source
291 vector *vm_vec_avg4(vector *dest,vector *src0,vector *src1,vector *src2,vector *src3);
293 //scales a vector in place. returns ptr to vector
294 #ifdef _INLINE_VECMAT
295 #define vm_vec_scale( dst, k ) do { \
302 void vm_vec_scale(vector *dest,float s);
305 //scales and copies a vector. returns ptr to dest
306 #ifdef _INLINE_VECMAT
307 #define vm_vec_copy_scale( dst, src, k ) do { \
309 (dst)->x = (src)->x * tmp_k; \
310 (dst)->y = (src)->y * tmp_k; \
311 (dst)->z = (src)->z * tmp_k; \
314 void vm_vec_copy_scale(vector *dest,vector *src,float s);
317 //scales a vector, adds it to another, and stores in a 3rd vector
318 //dest = src1 + k * src2
319 #ifdef _INLINE_VECMAT
320 #define vm_vec_scale_add( dst, src1, src2, k ) do { \
322 (dst)->x = (src1)->x + (src2)->x * tmp_k; \
323 (dst)->y = (src1)->y + (src2)->y * tmp_k; \
324 (dst)->z = (src1)->z + (src2)->z * tmp_k; \
327 void vm_vec_scale_add(vector *dest,vector *src1,vector *src2,float k);
331 //scales a vector and adds it to another
333 #ifdef _INLINE_VECMAT
334 #define vm_vec_scale_add2( dst, src, k ) do { \
336 (dst)->x += (src)->x * tmp_k; \
337 (dst)->y += (src)->y * tmp_k; \
338 (dst)->z += (src)->z * tmp_k; \
341 void vm_vec_scale_add2(vector *dest,vector *src,float k);
344 //scales a vector in place, taking n/d for scale. returns ptr to vector
346 #ifdef _INLINE_VECMAT
347 #define vm_vec_scale2( dst, n, d ) do { \
348 float tmp_k = (n)/(d); \
354 void vm_vec_scale2(vector *dest,float n,float d);
357 // finds the projection of source vector along a unit vector
358 // returns the magnitude of the component
359 float vm_vec_projection_parallel (vector *component, vector *src, vector *unit_vector);
361 // finds the projection of source vector onto a surface given by surface normal
362 void vm_vec_projection_onto_plane (vector *projection, vector *src, vector *normal);
364 //returns magnitude of a vector
365 float vm_vec_mag(vector *v);
367 // returns the square of the magnitude of a vector (useful if comparing distances)
368 float vm_vec_mag_squared(vector* v);
370 // returns the square of the distance between two points (fast and exact)
371 float vm_vec_dist_squared(vector *v0, vector *v1);
373 //computes the distance between two points. (does sub and mag)
374 float vm_vec_dist(vector *v0,vector *v1);
376 //computes an approximation of the magnitude of the vector
377 //uses dist = largest + next_largest*3/8 + smallest*3/16
378 float vm_vec_mag_quick(vector *v);
380 //computes an approximation of the distance between two points.
381 //uses dist = largest + next_largest*3/8 + smallest*3/16
382 float vm_vec_dist_quick(vector *v0,vector *v1);
385 //normalize a vector. returns mag of source vec
386 float vm_vec_copy_normalize(vector *dest,vector *src);
387 float vm_vec_normalize(vector *v);
389 // This version of vector normalize checks for the null vector before normalization.
390 // If it is detected, it generates a Warning() and returns the vector 1, 0, 0.
391 float vm_vec_normalize_safe(vector *v);
393 //normalize a vector. returns mag of source vec. uses approx mag
394 float vm_vec_copy_normalize_quick(vector *dest,vector *src);
395 float vm_vec_normalize_quick(vector *v);
397 //normalize a vector. returns mag of source vec. uses approx mag
398 float vm_vec_copy_normalize_quick_mag(vector *dest,vector *src);
399 float vm_vec_normalize_quick_mag(vector *v);
401 //return the normalized direction vector between two points
402 //dest = normalized(end - start). Returns mag of direction vector
403 //NOTE: the order of the parameters matches the vector subtraction
404 float vm_vec_normalized_dir(vector *dest,vector *end,vector *start);
405 float vm_vec_normalized_dir_quick_mag(vector *dest,vector *end,vector *start);
406 // Returns mag of direction vector
407 float vm_vec_normalized_dir_quick(vector *dest,vector *end,vector *start);
409 ////returns dot product of two vectors
410 #ifdef _INLINE_VECMAT
411 #define vm_vec_dotprod( v0, v1 ) (((v1)->x*(v0)->x)+((v1)->y*(v0)->y)+((v1)->z*(v0)->z))
412 #define vm_vec_dot( v0, v1 ) (((v1)->x*(v0)->x)+((v1)->y*(v0)->y)+((v1)->z*(v0)->z))
414 float vm_vec_dotprod(vector *v0,vector *v1);
415 #define vm_vec_dot vm_vec_dotprod
418 #ifdef _INLINE_VECMAT
419 #define vm_vec_dot3( x1, y1, z1, v ) (((x1)*(v)->x)+((y1)*(v)->y)+((z1)*(v)->z))
421 float vm_vec_dot3(float x,float y,float z,vector *v);
424 //computes cross product of two vectors. returns ptr to dest
425 //dest CANNOT equal either source
426 vector *vm_vec_crossprod(vector *dest,vector *src0,vector *src1);
427 #define vm_vec_cross vm_vec_crossprod
429 // test if 2 vectors are parallel or not.
430 int vm_test_parallel(vector *src0, vector *src1);
432 //computes surface normal from three points. result is normalized
433 //returns ptr to dest
434 //dest CANNOT equal either source
435 vector *vm_vec_normal(vector *dest,vector *p0,vector *p1,vector *p2);
437 //computes non-normalized surface normal from three points.
438 //returns ptr to dest
439 //dest CANNOT equal either source
440 vector *vm_vec_perp(vector *dest,vector *p0,vector *p1,vector *p2);
442 //computes the delta angle between two vectors.
443 //vectors need not be normalized. if they are, call vm_vec_delta_ang_norm()
444 //the forward vector (third parameter) can be NULL, in which case the absolute
445 //value of the angle in returned. Otherwise the angle around that vector is
447 float vm_vec_delta_ang(vector *v0,vector *v1,vector *fvec);
449 //computes the delta angle between two normalized vectors.
450 float vm_vec_delta_ang_norm(vector *v0,vector *v1,vector *fvec);
452 //computes a matrix from a set of three angles. returns ptr to matrix
453 matrix *vm_angles_2_matrix(matrix *m,angles *a);
455 // Computes a matrix from a single angle.
456 // angle_index = 0,1,2 for p,b,h
457 matrix *vm_angle_2_matrix(matrix *m, float a, int angle_index);
459 //computes a matrix from a forward vector and an angle
460 matrix *vm_vec_ang_2_matrix(matrix *m,vector *v,float a);
462 //computes a matrix from one or more vectors. The forward vector is required,
463 //with the other two being optional. If both up & right vectors are passed,
464 //the up vector is used. If only the forward vector is passed, a bank of
466 //returns ptr to matrix
467 matrix *vm_vector_2_matrix(matrix *m,vector *fvec,vector *uvec,vector *rvec);
469 //this version of vector_2_matrix requires that the vectors be more-or-less
470 //normalized and close to perpendicular
471 matrix *vm_vector_2_matrix_norm(matrix *m,vector *fvec,vector *uvec,vector *rvec);
473 //rotates a vector through a matrix. returns ptr to dest vector
474 //dest CANNOT equal either source
475 vector *vm_vec_rotate(vector *dest,vector *src,matrix *m);
477 //rotates a vector through the transpose of the given matrix.
478 //returns ptr to dest vector
479 //dest CANNOT equal source
480 // This is a faster replacement for this common code sequence:
481 // vm_copy_transpose_matrix(&tempm,src_matrix);
482 // vm_vec_rotate(dst_vec,src_vect,&tempm);
484 // vm_vec_unrotate(dst_vec,src_vect, src_matrix)
486 // THIS DOES NOT ACTUALLY TRANSPOSE THE SOURCE MATRIX!!! So if
487 // you need it transposed later on, you should use the
488 // vm_vec_transpose() / vm_vec_rotate() technique.
489 vector *vm_vec_unrotate(vector *dest,vector *src,matrix *m);
491 //transpose a matrix in place. returns ptr to matrix
492 matrix *vm_transpose_matrix(matrix *m);
493 #define vm_transpose(m) vm_transpose_matrix(m)
495 //copy and transpose a matrix. returns ptr to matrix
496 //dest CANNOT equal source. use vm_transpose_matrix() if this is the case
497 matrix *vm_copy_transpose_matrix(matrix *dest,matrix *src);
498 #define vm_copy_transpose(dest,src) vm_copy_transpose_matrix((dest),(src))
500 //mulitply 2 matrices, fill in dest. returns ptr to dest
501 //dest CANNOT equal either source
502 matrix *vm_matrix_x_matrix(matrix *dest,matrix *src0,matrix *src1);
504 //extract angles from a matrix
505 angles *vm_extract_angles_matrix(angles *a,matrix *m);
507 //extract heading and pitch from a vector, assuming bank==0
508 angles *vm_extract_angles_vector(angles *a,vector *v);
510 //make sure matrix is orthogonal
511 void vm_orthogonalize_matrix(matrix *m_src);
513 // like vm_orthogonalize_matrix(), except that zero vectors can exist within the
514 // matrix without causing problems. Valid vectors will be created where needed.
515 void vm_fix_matrix(matrix *m);
517 //Rotates the orient matrix by the angles in tangles and then
518 //makes sure that the matrix is orthogonal.
519 void vm_rotate_matrix_by_angles( matrix *orient, angles *tangles );
521 //compute the distance from a point to a plane. takes the normalized normal
522 //of the plane (ebx), a point on the plane (edi), and the point to check (esi).
523 //returns distance in eax
524 //distance is signed, so negative dist is on the back of the plane
525 float vm_dist_to_plane(vector *checkp,vector *norm,vector *planep);
527 // Given mouse movement in dx, dy, returns a 3x3 rotation matrix in RotMat.
528 // Taken from Graphics Gems III, page 51, "The Rolling Ball"
530 //if ( (Mouse.dx!=0) || (Mouse.dy!=0) ) {
531 // vm_trackball( Mouse.dx, Mouse.dy, &MouseRotMat );
532 // vm_matrix_x_matrix(&tempm,&LargeView.ev_matrix,&MouseRotMat);
533 // LargeView.ev_matrix = tempm;
535 void vm_trackball( int idx, int idy, matrix * RotMat );
537 // Find the point on the line between p0 and p1 that is nearest to int_pnt.
538 // Stuff result in nearest_point.
539 // Return value indicated where on the line *nearest_point lies. Between 0.0f and 1.0f means it's
540 // in the line segment. Positive means beyond *p1, negative means before *p0. 2.0f means it's
542 float find_nearest_point_on_line(vector *nearest_point, vector *p0, vector *p1, vector *int_pnt);
544 float vm_vec_dot_to_point(vector *dir, vector *p1, vector *p2);
546 void compute_point_on_plane(vector *q, plane *planep, vector *p);
548 // ----------------------------------------------------------------------------
549 // computes the point on a plane closest to a given point (which may be on the plane)
551 // inputs: new_point => point on the plane [result]
552 // point => point to compute closest plane point
553 // plane_normal => plane normal
554 // plane_point => plane point
555 void vm_project_point_onto_plane(vector *new_point, vector *point, vector *plane_normal, vector *plane_point);
558 // Returns fairly random vector, "quick" normalized
559 void vm_vec_rand_vec_quick(vector *rvec);
561 // Given an point "in" rotate it by "angle" around an
562 // arbritary line defined by a point on the line "line_point"
563 // and the normalized line direction, "line_dir"
564 // Returns the rotated point in "out".
565 void vm_rot_point_around_line(vector *out, vector *in, float angle, vector *line_point, vector *line_dir);
567 // Given two position vectors, return 0 if the same, else non-zero.
568 int vm_vec_cmp( vector * a, vector * b );
570 // Given two orientation matrices, return 0 if the same, else non-zero.
571 int vm_matrix_cmp( matrix * a, matrix * b );
573 // Moves angle 'h' towards 'desired_angle', taking the shortest
574 // route possible. It will move a maximum of 'step_size' radians
575 // each call. All angles in radians.
576 void vm_interp_angle( float *h, float desired_angle, float step_size );
578 // check a matrix for zero rows and columns
579 int vm_check_matrix_for_zeros(matrix *m);
581 // see if two vectors are identical
582 int vm_vec_same(vector *v1, vector *v2);
584 // Interpolate from a start matrix toward a goal matrix, minimizing time between orientations.
585 // Moves at maximum rotational acceleration toward the goal when far and then max deceleration when close.
586 // Subject to constaints on rotational velocity and angular accleleration.
587 // Returns next_orientation valid at time delta_t.
588 void vm_matrix_interpolate(matrix *goal_orient, matrix *start_orient, vector *rotvel_in, float delta_t,
589 matrix *next_orient, vector *rotvel_out, vector *rotvel_limit, vector *acc_limit, int no_overshoot=0);
591 // Interpolate from a start forward vec toward a goal forward vec, minimizing time between orientations.
592 // Moves at maximum rotational acceleration toward the goal when far and then max deceleration when close.
593 // Subject to constaints on rotational velocity and angular accleleration.
594 // Returns next forward vec valid at time delta_t.
595 void vm_forward_interpolate(vector *goal_fvec, matrix *orient, vector *rotvel_in, float delta_t, float delta_bank,
596 matrix *next_orient, vector *rotvel_out, vector *vel_limit, vector *acc_limit, int no_overshoot=0);
598 // Find the bounding sphere for a set of points (center and radius are output parameters)
599 void vm_find_bounding_sphere(vector *pnts, int num_pnts, vector *center, float *radius);
601 // Version of atan2() that is safe for optimized builds
602 float atan2_safe(float x, float y);
604 // Translates from world coordinates to body coordinates
605 vector* vm_rotate_vec_to_body(vector *body_vec, vector *world_vec, matrix *orient);
607 // Translates from body coordinates to world coordiantes
608 vector* vm_rotate_vec_to_world(vector *world_vec, vector *body_vec, matrix *orient);
610 // estimate next orientation matrix as extrapolation of last and current
611 void vm_estimate_next_orientation(matrix *last_orient, matrix *current_orient, matrix *next_orient);
613 // Return true if all elements of *vec are legal, that is, not a NAN.
614 int is_valid_vec(vector *vec);
616 // Return true if all elements of *m are legal, that is, not a NAN.
617 int is_valid_matrix(matrix *m);
619 // Finds the rotation matrix corresponding to a rotation of theta about axis u
620 void vm_quaternion_rotate(matrix *m, float theta, vector *u);
622 // Takes a rotation matrix and returns the axis and angle needed to generate it
623 void vm_matrix_to_rot_axis_and_angle(matrix *m, float *theta, vector *rot_axis);
625 // interpolate between 2 vectors. t goes from 0.0 to 1.0. at
626 void vm_vec_interp_constant(vector *out, vector *v1, vector *v2, float t);
628 // randomly perturb a vector around a given (normalized vector) or optional orientation matrix
629 void vm_vec_random_cone(vector *out, vector *in, float max_angle, matrix *orient = NULL);
631 // given a start vector, an orientation and a radius, give a point on the plane of the circle
632 // if on_edge is 1, the point is on the very edge of the circle
633 void vm_vec_random_in_circle(vector *out, vector *in, matrix *orient, float radius, int on_edge);
635 // find the nearest point on the line to p. if dist is non-NULL, it is filled in
636 // returns 0 if the point is inside the line segment, -1 if "before" the line segment and 1 ir "after" the line segment
637 int vm_vec_dist_to_line(vector *p, vector *l0, vector *l1, vector *nearest, float *dist);