// Ray Plane Collision - returns true if collsion exists
bool Collision::RayPlane(const float& normalX, const float& normalY, const float& normalZ, float pointOnPlaneX, float pointOnPlaneY, float pointOnPlaneZ,
float initialX, float initialY, float initialZ, float directionX, float directionY, float directionZ,
Vector3d p1, Vector3d p2, Vector3d p3, Vector3d p4, float* distance, Vector3d* collisionPoint){
// if the dot product == 0 then there is no collision
if((directionX * normalX + directionY * normalY + directionZ * normalZ) == 0){
return false;
}
float t = ((pointOnPlaneX * normalX + pointOnPlaneY * normalY + pointOnPlaneZ * normalZ -
normalX * initialX - normalY * initialY - normalZ * initialZ) /
(directionX * normalX + directionY * normalY + directionZ * normalZ));
// if t is a negative.....or (in this case) < 0 the intersection point
// is in the opposite direction... this indicates there is no collision
// i like to think as t representing scalar time here....since time is directed
// along a negative axis (which cant be)...it would denote no collision and evaluate to false.
if(t < 0){
return false;
}
// intialize a point that is used for testing the collision of the ray and a triangle of the plane.
float x = initialX + t * directionX;
float y = initialY + t * directionY;
float z = initialZ + t * directionZ;
Vector3d rayPoint(x, y, z);
float precision = 0.3;
// test to see if the sum of the three sub triangles equals the triangle from which they
// are derived...precision is used here in case the subtraction of the triangles are off by say like .0000000001
// exgerated i know, but used to illustrate the point. p1, p2, p3, and p4 are the vertices of the plane.
// the first test in the if statement is for the first triangle after the quad was subdivided
// simularly the second test in the if statement is for the other triangle.
if(std::abs(triangleArea(p1, p2, p3) - (triangleArea(p1, p2, rayPoint) +
triangleArea(p2, p3, rayPoint) + triangleArea(p1, p3, rayPoint))) < precision ||
std::abs(triangleArea(p1, p3, p4) - (triangleArea(p1, p3, rayPoint) +
triangleArea(p3, p4, rayPoint) + triangleArea(p1, p4, rayPoint))) < precision){
if(distance != NULL){
(*distance) = t;
if(collisionPoint != NULL){
collisionPoint->setX(x);
collisionPoint->setY(y);
collisionPoint->setZ(z);
}
}
return true;
}
return false;
}
int main()
{
Vec3 rayPoint(0,0,20);
Vec3 rayDirn(0,0,-1);
Vec3 triA(-1,-1,0);
Vec3 triB(1,-1,0);
Vec3 triC(2,1,0);
if(CalcRayTriIntersection(rayPoint,rayDirn,
triA,triB,triC))
{
std::cout << "Ray intersects triangle!\n";
}
else
{
std::cout << "Ray misses triangle!\n";
}
return 0;
}
