Raytracing

  
#define FLOAT2INTCAST(f) (*((int *)(&f)))
#define FLOAT2UINTCAST(f) (*((unsigned int *)(&f)))

static inline float det3x3(float a1, float a2, float a3,
					float b1, float b2, float b3,
					float c1, float c2, float c3)
{
   return  a1 * ( b2 * c3 - b3 * c2)
		   - b1 * ( a2 * c3 - a3 * c2)
		   + c1 * ( a2 * b3 - a3 * b2);
}

static inline BOOL intersectTri(Point3 &R0, Point3 &Rd, float &dist, float maxLen, dFace &tri/*, Point3 &baryCoord, Point3 &hitPos*/)
{
	float baryCoord;

	float Vd = tri.p.n.x * Rd.x + tri.p.n.y * Rd.y + tri.p.n.z * Rd.z;
	if (FLOAT2UINTCAST(Vd) <= 0x80000000U)		// [Vd >= 0.0f] this checks for backfacing

		return FALSE;

	float V0 = -(tri.p.n.x * R0.x + tri.p.n.y * R0.y + tri.p.n.z * R0.z + tri.p.d);
	float t = V0 / Vd;							// Solve the plane equation, get the distance to the intersection point


	if (FLOAT2UINTCAST(t) > 0x80000000U ||		// [t < 0.0f]

		t >= maxLen)							// [t >= maxLen] and this checks if the tri is behind the ray (negative)

		return FALSE;							// or bigger than an already recorded hit


	// Intersection with plane.

	Point3 Pi = Point3(R0.x+Rd.x*t, R0.y+Rd.y*t, R0.z+Rd.z*t);

	// Get the barycentric coordinates of the hitPoint.

	// If any of the components are > 1.0 the hit is outside the triangle


	// I pulled the function into this one here, since we only need to determine

	// further barycentric coordinates if the previous ones are already valid


	baryCoord = det3x3(Pi.x, Pi.y, Pi.z,
						 tri.b.x, tri.b.y, tri.b.z,
						 tri.c.x, tri.c.y, tri.c.z) * tri.area;

	if (FLOAT2UINTCAST(baryCoord) <= 0x80000000U && FLOAT2INTCAST(baryCoord) <= 0x3F800000) 
	{
		baryCoord = det3x3(tri.a.x, tri.a.y, tri.a.z,
							 Pi.x, Pi.y, Pi.z,
							 tri.c.x, tri.c.y, tri.c.z) * tri.area;

		if (FLOAT2UINTCAST(baryCoord) <= 0x80000000U && FLOAT2INTCAST(baryCoord) <= 0x3F800000) 
		{
			baryCoord = det3x3(tri.a.x, tri.a.y, tri.a.z,
								 tri.b.x, tri.b.y, tri.b.z,
								 Pi.x, Pi.y, Pi.z) * tri.area;

			if (FLOAT2UINTCAST(baryCoord) <= 0x80000000U && FLOAT2INTCAST(baryCoord) <= 0x3F800000) 
			{
				dist = t;
				return TRUE;
			}
		}
	}

	return FALSE;
}
  

  
| a1  b1  c1 |
| a2  b2  c2 |
| a3  b3  c3 |
  

  
Point3 &R0        // The origin of the ray

Point3 &Rd        // The direction unit vector of the ray

float &dist       // This is actually for output, contains the distance to the intersection

float maxLen      // The maximum already recorded hit distance

dFace &tri        // A triangle

  

    
bool intersect_triangle(ray ray,v3 a,v3 b,v3 c) {
	v3 e0 = b - a;
	v3 e1 = c - a;
	v3 p = ray.dir.cross(e1);
	f32 det = e0.dp3(p); 
	v3 t = ray.orig - a;
	f32 u = t.dp3(p); 
	v3 q = t.cross(e0);
	f32 v = ray.dir.dp3(q);
#ifdef CHECK_ONLY

	return det>0&&v>0.f&&u+v<det&&u>0.f&&u<det;
#else
	u /= det;
	v /= det;
	return det>0&&v>0.f&&1.f-u-v>0&&u>0.f&&1.f-u>0.f;
#endif
}
15-;21*;7+
    

    
bool intersect_triangle(ray ray,v3 a,v3 b,v3 c,f32 old_t,f32& new_t,f32& new_u,f32& new_v) {
	v3 e1 = c - a;
	v3 p = ray.dir.cross(e1);
	v3 t = ray.orig - a;
	f32 det = e0.dp3(p);
	if(det<=0.f) return false;
	t /= det;
	if(t<=0.f || t>=old_t) return false;
	f32 u = t.dp3(p);
	if(u<=0.f || u>=det) return false;
	v3 e0 = b - a;
	v3 q = t.cross(e0);
	f32 v = ray.dir.dp3(q);
	if(v<=0.f || u+v>=det) return false;
	u /= det;
	v /= det;
	new_t = t;
	new_u = u;
	new_v = v;
	return true;
}