Silhouette below 3D model There are some 3D applications which can cast shadow or silhouette below 3D models. They render pretty fast and smooth. I wonder what kind of technology is the standard procedure to get 3D model shadow/silhouette.
For example is there any C++ library like libigl or CGAL to get shadow/silhouette pretty fast? Or maybe GLSL shading is used? Any hint would be appreciated on the standard technology stack.
There is a trick to shadows like this, but only this exact usecase. While you can certainly draw a true shadow using many techniques. The trick is you can just scale the object flat onto the floor plane.
So all you need to do is draw the object 2 times one time with a matrix that is scaled to zero on the floor axis. You can also use this technique to draw shadows that arent entirely top down by adding skew to counter the now rotated shadow.
This is super easy to implement. No extra cameras. But works only on one plane. This is a special case of shadow volumes without the need to draw the volumes.