void IrrlichtRenderTarget::unprojectPoint(const GeometryBuffer& buff,
const glm::vec& p_in,
glm::vec& p_out) const
{
if (!d_matrixValid)
updateMatrix();
const IrrlichtGeometryBuffer& gb =
static_cast<const IrrlichtGeometryBuffer&>(buff);
const irr::f32 midx = d_area.getWidth() * 0.5f;
const irr::f32 midy = d_area.getHeight() * 0.5f;
// viewport matrix
const irr::f32 vpmat_[] =
{
midx, 0, 0, 0,
0, -midy, 0, 0,
0, 0, 1, 0,
d_area.left() + midx, d_area.top() + midy, 0, 1
};
irr::core::matrix4 vpmat;
vpmat.setM(vpmat_);
// matrices used for projecting and unprojecting points
const irr::core::matrix4 proj(gb.getMatrix() * d_matrix * vpmat);
irr::core::matrix4 unproj(proj);
unproj.makeInverse();
irr::core::vector3df in;
// unproject the ends of the ray
in.X = midx;
in.Y = midy;
in.Z = -d_viewDistance;
irr::core::vector3df r1;
unproj.transformVect(r1, in);
in.X = p_in.d_x;
in.Y = p_in.d_y;
in.Z = 0;
irr::core::vector3df r2;
unproj.transformVect(r2, in);
// calculate vector of picking ray
const irr::core::vector3df rv(r1 - r2);
// project points to orientate them with GeometryBuffer plane
in.X = 0.0;
in.Y = 0.0;
irr::core::vector3df p1;
proj.transformVect(p1, in);
in.X = 1.0;
in.Y = 0.0;
irr::core::vector3df p2;
proj.transformVect(p2, in);
in.X = 0.0;
in.Y = 1.0;
irr::core::vector3df p3;
proj.transformVect(p3, in);
// calculate the plane normal
const irr::core::vector3df pn((p2 - p1).crossProduct(p3 - p1));
// calculate distance from origin
const irr::f32 plen = pn.getLength();
const irr::f32 dist = -(p1.X * (pn.X / plen) +
p1.Y * (pn.Y / plen) +
p1.Z * (pn.Z / plen));
// calculate intersection of ray and plane
const irr::f32 pn_dot_rv = pn.dotProduct(rv);
const irr::f32 tmp = pn_dot_rv != 0.0 ?
(pn.dotProduct(r1) + dist) / pn_dot_rv :
0.0f;
p_out.d_x = static_cast<float>(r1.X - rv.X * tmp) * d_viewDistance;
p_out.d_y = static_cast<float>(r1.Y - rv.Y * tmp) * d_viewDistance;
}
