[Algorithms] Re: [GDAlgorithms-list digest, Vol 1 #103 - 2 msgs]

[Sohaib A. <soh...@us...>]

There you go David... this is from a raytracer i made... hope you understand
it...
To find out if the ray is tangent to the sphere, the dicriminant must be
zero... i think you'll figure it out.





COLORREF RayTracer::TraceRay(Vector3D endPoint, Vector3D direction, unsigned
int depth)
{
	float Ia, Kd, Ks, Kt, Krg, Ktg;
	float neta1=1.0f, neta2=0.9f, ns=1000.0f, nt=1000.0f, k=20.0f, dist=100.0f;
	Sphere *pSphere;
	Vector3D center, EO, H, H1, L, P, N, normal;
	float radius, v, disc, d, distfactor, LdotN;
	
	float t, tray=200000.0;
	Vector3D Ipoint, Inormal;
	COLORREF Ilocalcolor;
	
	bool Intersection=FALSE;

	for(unsigned int io = 0; io < theScene->objectList.size(); io++)
	{
		pSphere=(Sphere *)(theScene->objectList[io]);
		center=pSphere->center;
		radius=pSphere->radius;
		
		// Intersection Code
//////////////////////////////////////////////////////////////////////////////////////
		EO=center-endPoint;
		v=EO*direction;
		disc=radius*radius-((EO*EO)-v*v);
		if(disc<0)
			continue;			// Rejected, No intersection.
		// Intersection
		d=sqrt(disc);
		
		t=v-d;
		// Reject t if a closer intersection is already found i.e. t > t ray
		if(t<TOL || t>=tray)
			continue;

		P=endPoint+direction*t;
		normal=(P-center)/radius;
		normal.Normalize();
		
		// P: Intersection point, 
		// normal: Normal vector at P
//////////////////////////////////////////////////////////////////////////////////////
		Intersection=TRUE;
		tray=t;
		Ipoint=P;
		Inormal=normal;
		Ilocalcolor=pSphere->color;
		Ia= pSphere->Ia;
		Kd = pSphere->Kd;
		Ks = pSphere->Ks;
		Kt = pSphere->Kt;
		Krg= pSphere->Krg;
		Ktg= pSphere->Ktg;
		
		continue;

	} // End For(Object3D)
........



Regards,
Sohaib Athar.

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