Issues with picking

Nibbie

Posts: 1
Joined: 2009.11

Post: #1

Nov 21, 2009 — 04:37 PM

I'm designing a program so that you can color the model by using picking. However, whenever I draw on the model, it appears on the back of the model at strange places. I don't know if I'm doing the ray-triangle intersection correctly. Here is my code:

Code:

bool isViewIntersect(vertex sPos0, vertex sPos1, vertex v0, vertex v1, vertex v2,vertex &center)

{

    vertex e1,e2,direction,h,s,q;

    float a,u,v,intersect;

    direction.x=sPos1.x-sPos0.x;

    direction.y=sPos1.y-sPos0.y;

    direction.z=sPos1.z-sPos0.z;

    normalize(direction);

    e1.x=v1.x-v0.x;

    e1.y=v1.y-v0.y;

    e1.z=v1.z-v0.z;

    e2.x=v2.x-v0.x;

    e2.y=v2.y-v0.y;

    e2.z=v2.z-v0.z;

    normalize(e1);

    normalize(e2);

    h.x=direction.y*e2.z-direction.z*e2.y;

    h.y=direction.x*e2.z-direction.z*e2.x;

    h.z=direction.y*e2.z-direction.z*e2.y;

    normalize(h);

    a=e1.x*h.x+e1.y*h.y+e1.z*h.z;

    if(a>-0.00001 && a<0.00001)

        return false;

    s.x=sPos0.x-v0.x;

    s.y=sPos0.y-v0.y;

    s.z=sPos0.z-v0.z;

    normalize(s);

    u=(s.x*h.x+s.y*h.y+s.z*h.z)/a;

    if(u<0.0 || u>1.0)

        return false;

    q.x=s.y*e1.z-s.z*e1.y;

    q.y=s.x*e1.z-s.z*e1.x;

    q.z=s.x*e1.y-s.y*e1.x;

    normalize(q);

    v=(direction.x*q.x+direction.y*q.y+direction.z*q.z)/a;

    if(v <0.0 || u+v>1.0)

        return false;

    intersect=(e2.x*q.x+e2.y*q.y+e2.z*q.z)/a;

    if(intersect>0.00001)

    {

        center.x=sPos0.x+intersect*direction.x;

        center.y=sPos0.y+intersect*direction.y;

        center.z=sPos0.z+intersect*direction.z;

        cout << center.x << " " << center.y << " " << center.z << endl;

        return true;

    }

    return false;

}

Please help! Thank you!

Possibly Related Threads...

Thread:		Author	Replies:	Views:	Last Post
	How do I do Color Picking?	dockode	2	4,128	Sep 24, 2011 08:02 PM Last Post: dockode
	Opengl picking problem (zip file)	papillon68	1	3,745	Mar 1, 2009 08:49 PM Last Post: chronus
	Picking and selection...	chalamov33	2	2,981	Mar 31, 2008 02:08 PM Last Post: wyrmmage
	glut picking clashes with drawing	wyrmmage	2	3,133	Jan 24, 2008 06:39 PM Last Post: wyrmmage
	picking glOrtho vs gluPerspective	rhiannon	0	3,082	Jun 6, 2005 02:20 PM Last Post: rhiannon