Initial upload

external/cglm/ray.h

@@ -0,0 +1,174 @@
+/*
+ * Copyright (c), Recep Aslantas.
+ *
+ * MIT License (MIT), http://opensource.org/licenses/MIT
+ * Full license can be found in the LICENSE file
+ */
+
+/*
+ Functions:
+   CGLM_INLINE bool glm_ray_triangle(vec3   origin,
+                                     vec3   direction,
+                                     vec3   v0,
+                                     vec3   v1,
+                                     vec3   v2,
+                                     float *d);
+ CGLM_INLINE bool glm_ray_sphere(vec3 origin,
+                                 vec3 dir,
+                                 vec4 s,
+                                 float * __restrict t1,
+                                 float * __restrict t2)
+ CGLM_INLINE void glm_ray_at(vec3 orig, vec3 dir, float t, vec3 point);
+*/
+
+#ifndef cglm_ray_h
+#define cglm_ray_h
+
+#include "vec3.h"
+
+/*!
+ * @brief Möller–Trumbore ray-triangle intersection algorithm
+ * 
+ * @param[in] origin         origin of ray
+ * @param[in] direction      direction of ray
+ * @param[in] v0             first vertex of triangle
+ * @param[in] v1             second vertex of triangle
+ * @param[in] v2             third vertex of triangle
+ * @param[in, out] d         distance to intersection
+ * @return whether there is intersection
+ */
+CGLM_INLINE
+bool
+glm_ray_triangle(vec3   origin,
+                 vec3   direction,
+                 vec3   v0,
+                 vec3   v1,
+                 vec3   v2,
+                 float *d) {
+  vec3        edge1, edge2, p, t, q;
+  float       det, inv_det, u, v, dist;
+  const float epsilon = 0.000001f;
+
+  glm_vec3_sub(v1, v0, edge1);
+  glm_vec3_sub(v2, v0, edge2);
+  glm_vec3_cross(direction, edge2, p);
+
+  det = glm_vec3_dot(edge1, p);
+  if (det > -epsilon && det < epsilon)
+    return false;
+
+  inv_det = 1.0f / det;
+  
+  glm_vec3_sub(origin, v0, t);
+
+  u = inv_det * glm_vec3_dot(t, p);
+  if (u < 0.0f || u > 1.0f)
+    return false;
+
+  glm_vec3_cross(t, edge1, q);
+
+  v = inv_det * glm_vec3_dot(direction, q);
+  if (v < 0.0f || u + v > 1.0f)
+    return false;
+
+  dist = inv_det * glm_vec3_dot(edge2, q);
+
+  if (d)
+    *d = dist;
+
+  return dist > epsilon;
+}
+
+/*!
+ * @brief ray sphere intersection
+ *
+ * returns false if there is no intersection if true:
+ *
+ * - t1 > 0, t2 > 0: ray intersects the sphere at t1 and t2 both ahead of the origin
+ * - t1 < 0, t2 > 0: ray starts inside the sphere, exits at t2
+ * - t1 < 0, t2 < 0: no intersection ahead of the ray ( returns false )
+ * - the caller can check if the intersection points (t1 and t2) fall within a
+ *   specific range (for example, tmin < t1, t2 < tmax) to determine if the
+ *   intersections are within a desired segment of the ray
+ *
+ * @param[in]  origin ray origin
+ * @param[out] dir    normalized ray direction
+ * @param[in]  s      sphere  [center.x, center.y, center.z, radii]
+ * @param[in]  t1     near point1 (closer to origin)
+ * @param[in]  t2     far point2 (farther from origin)
+ *
+ * @returns whether there is intersection
+ */
+CGLM_INLINE
+bool 
+glm_ray_sphere(vec3 origin,
+               vec3 dir,
+               vec4 s,
+               float * __restrict t1,
+               float * __restrict t2) {
+  vec3  dp;
+  float r2, ddp, dpp, dscr, q, tmp, _t1, _t2;
+
+  glm_vec3_sub(s, origin, dp);
+
+  ddp = glm_vec3_dot(dir, dp);
+  dpp = glm_vec3_norm2(dp);
+
+  /* compute the remedy term for numerical stability */
+  glm_vec3_mulsubs(dir, ddp, dp); /* dp: remedy term */
+
+  r2   = s[3] * s[3];
+  dscr = r2 - glm_vec3_norm2(dp);
+
+  if (dscr < 0.0f) {
+    /* no intersection */
+    return false;
+  }
+
+  dscr = sqrtf(dscr);
+  q    = (ddp >= 0.0f) ? (ddp + dscr) : (ddp - dscr);
+
+  /*
+     include Press, William H., Saul A. Teukolsky,
+     William T. Vetterling, and Brian P. Flannery,
+     "Numerical Recipes in C," Cambridge University Press, 1992.
+   */
+  _t1 = q;
+  _t2 = (dpp - r2) / q;
+
+  /* adjust t1 and t2 to ensure t1 is the closer intersection */
+  if (_t1 > _t2) {
+    tmp = _t1;
+    _t1 = _t2;
+    _t2 = tmp;
+  }
+
+  *t1 = _t1;
+  *t2 = _t2;
+
+  /* check if the closest intersection (t1) is behind the ray's origin */
+  if (_t1 < 0.0f && _t2 < 0.0f) {
+    /* both intersections are behind the ray, no visible intersection */
+    return false;
+  }
+
+  return true;
+}
+
+/*!
+ * @brief point using t by 𝐏(𝑡)=𝐀+𝑡𝐛
+ *
+ * @param[in]  orig  origin of ray
+ * @param[in]  dir   direction of ray
+ * @param[in]  t     parameter
+ * @param[out] point point at t
+ */
+CGLM_INLINE
+void
+glm_ray_at(vec3 orig, vec3 dir, float t, vec3 point) {
+  vec3 dst;
+  glm_vec3_scale(dir, t, dst);
+  glm_vec3_add(orig, dst, point);
+}
+
+#endif