docs for new ray functions

docs/source/ray.rst

@@ -13,6 +13,8 @@ Table of contents (click to go):
 Functions:
 
 1. :c:func:`glm_ray_triangle`
+#. :c:func:`glm_ray_sphere`
+#. :c:func:`glm_ray_at`
 
 Functions documentation
 ~~~~~~~~~~~~~~~~~~~~~~~
@@ -29,3 +31,37 @@ Functions documentation
       | *[in]*       **v2**            third vertex of triangle
       | *[in, out]*  **d**             float pointer to save distance to intersection
       | *[out]*      **intersection**  whether there is intersection
+
+.. c:function:: bool glm_ray_sphere(vec3 origin, vec3 dir, vec4 s, float * __restrict t1, float * __restrict t2)
+
+    ray sphere intersection
+
+    - 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
+    - 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
+
+    Parameters:
+      | *[in]*   **origin**  ray origin
+      | *[in]*   **dir**     normalized ray direction
+      | *[in]*   **s**       sphere  [center.x, center.y, center.z, radii]
+      | *[out]*  **t1**      near point1 (closer to origin)
+      | *[out]*  **t2**      far point2 (farther from origin)
+
+    Return:
+      | whether there is intersection
+
+.. c:function:: bool  glm_ray_at(vec3 orig, vec3 dir, float t, vec3 point)
+
+    point using t by 𝐏(𝑡)=𝐀+𝑡𝐛
+
+    Parameters:
+      | *[in]*   **origin**  ray origin
+      | *[in]*   **dir**     ray direction
+      | *[out]*  **t**       parameter
+      | *[out]*  **point**   point at t
+
+    Return:
+      | point at t