// static
Box3f Box3f::united( const Box3f& b0, const Box3f& b1 )
{
Vector3f unitedMin = libcgt::core::math::minimum(
b0.leftBottomBack(), b1.leftBottomBack() );
Vector3f unitedMax = libcgt::core::math::maximum(
b0.rightTopFront(), b1.rightTopFront() );
return{ unitedMin, unitedMax - unitedMin };
}
bool intersectLine( const Box3f& box,
const Vector3f& rayOrigin, const Vector3f& rayDirection,
float& tNear, float& tFar )
{
assert( box.isStandard() );
assert( !box.isEmpty() );
// Compute t to each face.
Vector3f rcpDir = 1.0f / rayDirection;
// Three "bottom" faces (min of the box).
Vector3f tBottom = rcpDir * ( box.origin - rayOrigin );
// three "top" faces (max of the box)
Vector3f tTop = rcpDir * ( box.rightTopFront() - rayOrigin );
// find the smallest and largest distances along each axis
Vector3f tMin = libcgt::core::math::minimum( tBottom, tTop );
Vector3f tMax = libcgt::core::math::maximum( tBottom, tTop );
// tNear is the largest tMin
tNear = libcgt::core::math::maximum( tMin );
// tFar is the smallest tMax
tFar = libcgt::core::math::minimum( tMax );
return tFar > tNear;
}
// static
bool Box3f::intersect( const Box3f& b0, const Box3f& b1, Box3f& intersection )
{
Vector3f minimum = libcgt::core::math::maximum(
b0.leftBottomBack(), b1.leftBottomBack() );
Vector3f maximum = libcgt::core::math::minimum(
b0.rightTopFront(), b1.rightTopFront() );
if( minimum.x < maximum.x &&
minimum.y < maximum.y &&
minimum.z < maximum.z )
{
intersection.origin = minimum;
intersection.size = maximum - minimum;
return true;
}
return false;
}
bool carefulIntersectBoxRay( const Box3f& box,
const Vector3f& rayOrigin, const Vector3f& rayDirection,
float& t0, float& t1, int& t0Face, int& t1Face,
float rayTMin, float rayTMax )
{
assert( box.isStandard() );
assert( !box.isEmpty() );
t0 = rayTMin;
t1 = rayTMax;
t0Face = -1;
t1Face = -1;
// Compute t to each face.
Vector3f rcpDir = 1.0f / rayDirection;
Vector3f boxMax = box.rightTopFront();
for( int i = 0; i < 3; ++i )
{
// Compute the intersection between the line and the slabs along the
// i-th axis, parameterized as [tNear, tFar].
float rcpDir = 1.0f / rayDirection[ i ];
float tNear = rcpDir * ( box.origin[ i ] - rayOrigin[ i ] );
float tFar = rcpDir * ( boxMax[ i ] - rayOrigin[ i ] );
// Which face we're testing against.
int nearFace = 2 * i;
int farFace = 2 * i + 1;
// Swap such that tNear < tFAr.
if( tNear > tFar )
{
std::swap( tNear, tFar );
std::swap( nearFace, farFace );
}
// Compute the set intersection between [tNear, tFar] and [t0, t1].
if( tNear > t0 )
{
t0 = tNear;
t0Face = nearFace;
}
if( tFar < t1 )
{
t1 = tFar;
t1Face = farFace;
}
// Early abort if the range is empty.
if( t0 > t1 )
{
return false;
}
}
return true;
}