Function FindHitpointUV

physics/collide.cpp:930–976

finds the uv coords of the given point on the given seg & side fills in u & v. if l is non-NULL fills it in also

// finds the uv coords of the given point on the given seg & side
// fills in u & v. if l is non-NULL fills it in also
void FindHitpointUV(float *u, float *v, vector *point, room *rp, int facenum) {
  face *fp = &rp->faces[facenum];
  int ii, jj;
  vec2d pnt[3], checkp, vec0, vec1;
  float *t;
  float k0, k1;
  int i;

  // 1. find what plane to project this wall onto to make it a 2d case

  GetIJ(&fp->normal, &ii, &jj);

  // 2. compute u,v of intersection point

  // Copy face points into 2d verts array
  for (i = 0; i < 3; i++) {
    t = &rp->verts[fp->face_verts[i]].x;
    pnt[i].i = t[ii];
    pnt[i].j = t[jj];
  }
  t = &point->x;
  checkp.i = t[ii];
  checkp.j = t[jj];

  // vec from 1 -> 0
  vec0.i = pnt[0].i - pnt[1].i;
  vec0.j = pnt[0].j - pnt[1].j;

  // vec from 1 -> 2
  vec1.i = pnt[2].i - pnt[1].i;
  vec1.j = pnt[2].j - pnt[1].j;

  k1 = -((cross(&checkp, &vec0) + cross(&vec0, &pnt[1])) / cross(&vec0, &vec1));
  if (fabsf(vec0.i) > fabsf(vec0.j))
    k0 = ((-k1 * vec1.i) + checkp.i - pnt[1].i) / vec0.i;
  else
    k0 = ((-k1 * vec1.j) + checkp.j - pnt[1].j) / vec0.j;

  // mprintf(0," k0,k1  = %x,%x\n",k0,k1);

  *u = fp->face_uvls[1].u + (k0 * (fp->face_uvls[0].u - fp->face_uvls[1].u)) +
       (k1 * (fp->face_uvls[2].u - fp->face_uvls[1].u));
  *v = fp->face_uvls[1].v + (k0 * (fp->face_uvls[0].v - fp->face_uvls[1].v)) +
       (k1 * (fp->face_uvls[2].v - fp->face_uvls[1].v));

  // mprintf(0," u,v    = %x,%x\n",*u,*v);
}

// Creates some effects where a weapon has collided with a wall
void DoWallEffects(object *weapon, int surface_tmap) {