////////////////////////////////////////////////////
// Fast ray/AABB intersection test.
// Implementation inspired by zacharmarz.
// https://gamedev.stackexchange.com/questions/18436/most-efficient-aabb-vs-ray-collision-algorithms
////////////////////////////////////////////////////
bool Intersections::aabbIntersect( boundingBox bbox, glm::vec3 ray_o, glm::vec3 ray_dir, float &t_near, float &t_far )
{
glm::vec3 dirfrac( 1.0f / ray_dir.x, 1.0f / ray_dir.y, 1.0f / ray_dir.z );
float t1 = ( bbox.min.x - ray_o.x ) * dirfrac.x;
float t2 = ( bbox.max.x - ray_o.x ) * dirfrac.x;
float t3 = ( bbox.min.y - ray_o.y ) * dirfrac.y;
float t4 = ( bbox.max.y - ray_o.y ) * dirfrac.y;
float t5 = ( bbox.min.z - ray_o.z ) * dirfrac.z;
float t6 = ( bbox.max.z - ray_o.z ) * dirfrac.z;
float tmin = std::max( std::max( std::min( t1, t2 ), std::min( t3, t4 ) ), std::min( t5, t6 ) );
float tmax = std::min( std::min( std::max( t1, t2 ), std::max( t3, t4 ) ), std::max( t5, t6 ) );
// If tmax < 0, ray intersects AABB, but entire AABB is behind ray, so reject.
if ( tmax < 0.0f ) {
return false;
}
// If tmin > tmax, ray does not intersect AABB.
if ( tmin > tmax ) {
return false;
}
t_near = tmin;
t_far = tmax;
return true;
}
std::pair<bool, float> BoundingBox::intersects(
const glm::vec3& origin, const glm::vec3& direction) const
{
// r.dir is unit direction vector of ray
glm::vec3 dirfrac(1.0f / direction.x, 1.0f / direction.y, 1.0f / direction.z);
// lb is the corner of AABB with minimal coordinates - left bottom,
// rt is maximal corner
// r.org is the origin of ray
float t1 = (_min.x - origin.x)*dirfrac.x;
float t2 = (_max.x - origin.x)*dirfrac.x;
float t3 = (_min.y - origin.y)*dirfrac.y;
float t4 = (_max.y - origin.y)*dirfrac.y;
float t5 = (_min.z - origin.z)*dirfrac.z;
float t6 = (_max.z - origin.z)*dirfrac.z;
float tmin = glm::max(
glm::max(glm::min(t1, t2), glm::min(t3, t4)),
glm::min(t5, t6));
float tmax = glm::min(
glm::min(glm::max(t1, t2), glm::max(t3, t4)),
glm::max(t5, t6));
// if tmax < 0, ray (line) is intersecting AABB, but whole AABB is behing us
if (tmax < 0)
{
return {false, tmax};
}
// if tmin > tmax, ray doesn't intersect AABB
if (tmin > tmax)
{
return {false, tmax};
}
return {true, tmin};
}
