Voxel Instancing

Instancing is a dirty trick widely used in computer graphics. We are always trying to push the limits in terms of what we can render on screen. Instancing allows to repeat the same object many times in one scene. The object's model is stored only once in memory and we only need to store addition information for each of its occurrences in the scene. That is, their position and orientation. It makes a big difference. Without instancing most of the richness you see in current game worlds would be gone. Boulders, patches of vegetation, even trees and sometimes entire buildings are heavily instanced.

Instancing is a dirty trick because there is no instancing in the real world. Each pebble in that river bed is unique. We use this shortcut in virtual worlds because somehow it still does the trick. Maybe our brain is not able to detect these are all copies of the same object, or maybe it is something we just forgive because nobody has been able to show us anything better.

To the occurrence of each object we call an instance. The source model for all the same instances we can call a "class". This is pretty much the same concepts you find in object oriented programming.

In most game engines, which store all models as polygons, instancing is done at the polygonal level. In my case I saw the same advantages would apply if you had them in voxel form. Their memory footprint is constant, and they a blazing fast to bring into the world.

Translated to voxels, the class stores the voxel values that define the object. This can be done either in a regular grid, or an adaptive grid like an octree. Or, in any other form that makes sense to you. In my case I store them compressed using some form of Run-Length-Encoding. These classes may take one or two megabytes each, in compressed form. Each instance is a much smaller piece of information. It just needs to record where the instance is and to which class it belongs to.

You have seen a lot of this instancing system already in my videos and screenshots. It is how trees are made. But until now, only trees were using instancing. I had my tree generation tool produce the compressed classes directly.

This weekend I added a new feature to the Voxel Studio tool. It can now load a 3D mesh and create the instance data for it. Thanks to this I can have more interesting instances, like giant boulders, dilapidated houses, ruins, even pine trees!

Here are a few screenshots showing how a few instances can spice up the landscape. The last two show how you can carve and edit the instanced voxels. They are no different than voxels coming from any other source.