Thread by @delaneykingrox

Quick #gamedev #gameart lesson.

Interpenetration is when you stick an element of an object through another. In some cases it can be handy, but it isn't always the best idea.

In the early days of 3D, interpenetrating geo saved us a lot of polygons. But engines worked differently then... polygons where expensive.
In this example, if I welded the beam into the block, it would increase the polycount by whopping... wait for it... 6 whole triangles.

But the rules are different now, 3d cards use a whole new set of rules.

The texture takes up more memory than the mesh you save, so if you bake like this, some of the texture will be wasted.

Either way, the saving isn't as big as it used to be.

Now lets say we bake a high poly model onto this, the bake will have artefacts. You have two polys with vastly different normals- so the bake draws the stud details from two angles.

Now look at this bake. Mmmm... looks nice. This is an example of the different between interpenetrating geo and cut in.

By cutting in here, I have four vertices with normals at the point where the beam meets the stone. That changes the bakes normal, resulting in a bake that appears to be organic. That extra geo pays its rent.

Even when you have an object that needs to stick in like this, I will still slice the sticking through part close to touching the face. This puts the vertices in a place I can use them. You can often bend the normals to help blend the object into the other.

I cover this and all the other techniques from decades of polygon and pixel witchery in my forth coming book.

Stay tuned, poly pushers x.

And in the meantime buy me a coffee!

ko-fi.com/dellak