bool Ray::IntersectBox( Box3 a_box, matrix a_mat_transform )
{
// translate by position
a_mat_transform = a_mat_transform * matrix::Translation( a_box.GetCenter() );
v3 halfsize = a_box.Size()*0.5f;
float tmin = -FLT_MAX;
float tmax = FLT_MAX;
v4 nmin;
v4 nmax;
const v4 p = a_mat_transform.w - v4(m_pos,1.0f);
for ( size_t i=0; i!=3; ++i )
{
v4 box_basis_vector = a_mat_transform[i];
const float e = dot( box_basis_vector, p );
float f = dot( box_basis_vector, v4(m_dir,0.0f) );
if ( fabs(f) > EPSILON )
{
f = 1.0f/f;
float t1 = ( e + halfsize[i] ) * f;
float t2 = ( e - halfsize[i] ) * f;
float flip = 1.f;
if ( t1 > t2 )
{
// swap
float tmp = t1;
t1 = t2;
t2 = tmp;
flip = -flip;
}
if ( t1 > tmin ) { tmin = t1; nmin = a_mat_transform[i] * flip; }
if ( t2 < tmax ) { tmax = t2; nmax =-a_mat_transform[i] * flip; }
if ( tmin > tmax ) return false;
if ( tmax < 0.f ) return false;
}
else if ( ( ( -e - halfsize[i] ) > 0.f ) ||
( ( -e + halfsize[i] ) < 0.f ) )
{
// ray parallel to the stab
return false;
}
}
if ( tmin > 0.f )
return NewHit( tmin, nmin.xyz() );
return NewHit( tmax, nmax.xyz() );
}
bool Ray::IntersectTri( v3 a_pt0, v3 a_pt1, v3 a_pt2 )
{
v3 tri_normal = cross( a_pt1 - a_pt0, a_pt2 - a_pt0 );
const float vdotn = dot( tri_normal, m_dir );
// the ray direction is parallel to triangle plane, return no intersection
if ( fabs(vdotn) <= EPSILON )
return false;
// signed distance to intersection point
const float sd = dot( a_pt0-m_pos , tri_normal ) / vdotn;
if ( sd < 0.f )
return false;
const v3 i = m_pos + m_dir * sd;
if ( dot( cross( a_pt1-a_pt0, i-a_pt0 ), tri_normal ) < 0.f ) return false;
if ( dot( cross( a_pt2-a_pt1, i-a_pt1 ), tri_normal ) < 0.f ) return false;
if ( dot( cross( a_pt0-a_pt2, i-a_pt2 ), tri_normal ) < 0.f ) return false;
return NewHit( sd, tri_normal );
}
bool Ray::IntersectQuad( v3 a_pt0, v3 a_pt1, v3 a_pt2, v3 a_pt3 )
{
v3 normal = normalize( cross(a_pt1-a_pt0, a_pt2-a_pt0) );
const float vdotn = dot(m_dir, normal );
// the ray direction is parallel to triangle plane, return no intersection
if ( fabs(vdotn) <= EPSILON )
return false;
// signed distance to intersection point
const float sd = ( ( dot( a_pt0 - m_pos, normal ) ) / vdotn );
if ( sd < 0.f )
return false;
const v3 i = m_pos + m_dir * sd;
if ( dot( cross(a_pt1 - a_pt0, i - a_pt0 ), normal ) < 0.f ) return false;
if ( dot( cross(a_pt2 - a_pt1, i - a_pt1 ), normal ) < 0.f ) return false;
if ( dot( cross(a_pt3 - a_pt2, i - a_pt2 ), normal ) < 0.f ) return false;
if ( dot( cross(a_pt0 - a_pt3, i - a_pt3 ), normal ) < 0.f ) return false;
return NewHit( sd, normal );
}
bool Ray::IntersectPlane( Plane a_plane )
{
v3 normal = a_plane.GetNormal();
const float vdotn = dot( m_dir, normal );
if ( fabs(vdotn) <= EPSILON )
return false;
return NewHit( - dot( m_pos - m_pos, normal ) / vdotn, normal );
}
bool Ray::IntersectDisk( v3 a_center, float a_radius, v3 a_normal )
{
const float vdotn = dot( m_dir, a_normal );
// the ray direction is parallel to triangle plane, return no intersection
if ( fabs(vdotn) <= EPSILON )
return false;
// signed distance to intersection point
const float sd = ( dot(a_center, a_normal) - dot(m_pos, a_normal) ) / vdotn;
if ( sd < 0.f )
return false;
const v4 i = m_pos + m_dir * sd;
if ( lengthSqr( i - a_center ) > a_radius*a_radius )
return false;
return NewHit( sd, a_normal );
}
bool Ray::IntersectSphere( v3 center, float radius )
{
// http://wiki.cgsociety.org/index.php/Ray_Sphere_Intersection
v3 ray_pos_transformed = m_pos - center;
// Compute A, B and C coefficients
float a = dot(m_dir, m_dir);
float b = 2 * dot(m_dir, ray_pos_transformed);
float c = dot(ray_pos_transformed, ray_pos_transformed) - (radius * radius);
//Find discriminant
float disc = b * b - 4 * a * c;
// if discriminant is negative there are no real roots, so return
// false as ray misses sphere
if (disc < 0)
return false;
// compute q as described above
float distSqrt = sqrtf(disc);
float q;
if (b < 0)
q = (-b - distSqrt)/2.0f;
else
q = (-b + distSqrt)/2.0f;
// compute t0 and t1
float t0 = q / a;
float t1 = c / q;
// make sure t0 is smaller than t1
if (t0 > t1)
{
// if t0 is bigger than t1 swap them around
float temp = t0;
t0 = t1;
t1 = temp;
}
// if t1 is less than zero, the object is in the ray's negative direction
// and consequently the ray misses the sphere
if (t1 < 0)
return false;
float t;
// if t0 is less than zero, the intersection point is at t1
if (t0 < 0)
{
t = t1;
}
// else the intersection point is at t0
else
{
t = t0;
}
v3 sphere_pos = ray_pos_transformed + m_dir*t;
v3 normal = normalize(sphere_pos);
return NewHit(t, normal );
}
HitData *GetNextHit(HitData *hit)
{
if(hit->next == NULL)
hit->next = NewHit();
return hit->next;
}
