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# ray to box collision detection problems

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Hi

I am attempting to use a ray to box intersection within my program. It initially seems fine and seems to work ok for the object I am moving around my scene. It can calculate how far away from the object I am etc. I am also attempting to use it within a camera. The idea being to be able to fire a ray in the direction the camera is facing. If this hits the box return true else return false.

I am assuming it is something I am doing with the camera that is causing me errors?

Maybe to do with the way I am looking down the axis? I seem to either be able to get false positive most of the time or no positive.

The code for my ray to box intersection is

bool Collision::rayToBoxCollision(float boxX1,float boxX2, float boxY1, float boxY2, float boxZ1, float boxZ2, float rayStartX, float rayStartY, float rayStartZ,float rayDirectionX,float rayDirectionY, float rayDirectionZ, float angleOfRotation)
{

float tNear = -500;
float tFar = 500;
float T1Final;
float T2Final;
float T1;
float T2;
j = 0; // keep track of box edges

float boundingBox[] = {boxX1, boxX2,boxY1,boxY2,boxZ1,boxZ2}; // set up bounding box points
float raystartPoint[] = {rayStartX,rayStartY,rayStartZ}; // ray starting vector
float rayDirectionVector[] = {rayDirectionX,rayDirectionY,rayDirectionZ}; // ray direction vector
bool collision[] = {0,0,0};

for(int i = 0; i<3; i++) // loop around all arrays
{
tNear = -500;
tFar = 500;

if(raystartPoint == 0) // if ray is parrallel to box
{
if(raystartPoint < boundingBox[j] || raystartPoint > boundingBox[j+1]) // if its not within the box boundry
collision = false;
else
collision = true;
}

if(rayDirectionVector == 0)
rayDirectionVector += 1;

T1 = boundingBox[j] - raystartPoint;
T1Final = T1/rayDirectionVector; // calculate intersection Distance between bottom

T2 = boundingBox[j+1] - raystartPoint;
T2Final = T2/rayDirectionVector; //calculate intersection distance top

if(T1Final>T2Final) // if top and bottom are the wrong way round swap
{
float temp = T2Final;
T2Final = T1Final;
T1Final = temp;
}

if(T1Final>tNear) //clamp near collision to t1
{
tNear = T1Final;
}

if(T2Final < tFar) // clamp far collision to t2
{
tFar = T2Final;
}

rayTfar = tFar;
rayTNear = tNear;

rayArray = tNear;
rayArray[i+1] = tFar;

j += 2;

if(tNear > tFar)
collision = false;
else if(tFar<0)
collision = false;
else
collision = true;
}

if(collision[0] == true && collision[1] == true && collision[2] == true) // check x,y and z axis are all true
return true;
else
return false;

}

Is there something wrong here that I have missed? or is it the way I am shooting the ray from the camera?

Any help greatly appreciated

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