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src/util.cpp

@@ -75,6 +75,76 @@ bool ray_intersect(glm::vec3 ray_origin, glm::vec3 ray_dir, glm::vec3 plane_orig
     return true;
 };
 
+// see: http://geomalgorithms.com/a07-_distance.html
+// dist3D_Line_to_Line(): get the 3D minimum distance between 2 lines
+//    Input:  two 3D lines L1 and L2
+//    Return: the shortest distance between L1 and L2
+float lines_distance(const glm::vec3& p0a, const glm::vec3& p0b,
+    const glm::vec3& p1a, const glm::vec3& p1b)
+{
+    glm::vec3 u = p0b - p0a;
+    glm::vec3 v = p1b - p1a;
+    glm::vec3 w = p0a - p1a;
+    float    a = glm::dot(u,u); // always >= 0
+    float    b = glm::dot(u,v);
+    float    c = glm::dot(v,v); // always >= 0
+    float    d = glm::dot(u,w);
+    float    e = glm::dot(v,w);
+    float    D = a*c - b*b;     // always >= 0
+    float    sc, tc;
+
+    // compute the line parameters of the two closest points
+    if (D < 0.00001f) {          // the lines are almost parallel
+        sc = 0.0;
+        tc = (b>c ? d/b : e/c);    // use the largest denominator
+    }
+    else {
+        sc = (b*e - c*d) / D;
+        tc = (a*e - b*d) / D;
+    }
+
+    // get the difference of the two closest points
+    glm::vec3 dP = w + (sc * u) - (tc * v);  // =  L1(sc) - L2(tc)
+
+    return glm::length(dP);   // return the closest distance
+}
+
+bool segments_intersect_3d(const glm::vec3& p0a, const glm::vec3& p0b,
+    const glm::vec3& p1a, const glm::vec3& p1b, glm::vec3& out_pt, glm::vec2& out_hit_uv)
+{
+    float denom = ((p1b.y - p1a.y)*(p0b.x - p0a.x)) -
+                  ((p1b.x - p1a.x)*(p0b.y - p0a.y));
+
+    float nume_a = ((p1b.x - p1a.x)*(p0a.y - p1a.y)) -
+                   ((p1b.y - p1a.y)*(p0b.x - p1a.x));
+
+    float nume_b = ((p0b.x - p0a.x)*(p0a.y - p1a.y)) -
+                   ((p0b.y - p0a.y)*(p0a.x - p1a.x));
+
+    if(denom == 0.0f)
+    {
+        if(nume_a == 0.0f && nume_b == 0.0f)
+        {
+            return 0;//COINCIDENT;
+        }
+        return 0;//PARALLEL;
+    }
+
+    float ua = nume_a / denom;
+    float ub = nume_b / denom;
+
+    if(ua >= 0.0f && ua <= 1.0f && ub >= 0.0f && ub <= 1.0f)
+    {
+        // Get the intersection point.
+        out_pt.x = p0a.x + ua*(p0b.x - p0a.x);
+        out_pt.y = p0a.y + ua*(p0b.y - p0a.y);
+
+        return 1;//INTERESECTING;
+    }
+
+    return 0;//NOT_INTERESECTING;
+}
+
 // see: https://stackoverflow.com/questions/563198/how-do-you-detect-where-two-line-segments-intersect
 bool segments_intersect(const glm::vec2& p0a, const glm::vec2& p0b,
     const glm::vec2& p1a, const glm::vec2& p1b, glm::vec2& out_pt, glm::vec2& out_hit_uv)