It's a subtle change, but it means in the common case of rendering a glass cup with a two pass material if there are two cups that overlap it'll render the "inside" of both of them, then the "outside" causing the outside of one glass to appear between the inside and outside of the other, where as before they would appear properly as separate cups. It used to be when multiple objects using multi-pass materials were rendered they'd work like this: Other notes on option 2: As of Unity 5.6 they've changed the way multi-pass shaders are handled. Some people do something similar by using a dot product between the surface normal and the view direction, but this method both produces wrong results and is much more expensive! If you're using a single texture for both sides there's no reason not to use this option apart from most people don't seem to know about it. This is the method I use the vast majority of the time, and is by far the fastest as it doesn't double the geometry and requires very little shader work to implement. Single pass shader with culling off and using VFACE to flip the normal. However this is still doubling the rendered geometry so all of the negatives of option 1 still exist with basically none of the benefits.ģ. Basically you generally want the inside to render before the outside so they visually sort nicely, and you can get this with method 1 too if you control the triangle order carefully, but that's not something easily exposed in a lot of modeling tools. Two pass shaders are nice for transparent objects like glass cups as you can guarantee the order the order of rendering. Yes it doubles the vertex count, but that's not usually a limiting factor when it comes to rendering performance unless you're using rediculously high poly geometry, or on seriously old hardware or doing VR on mobile.Ģ. It also means it can be easily batched with "single sided" geometry. Manually doubling the geometry in the mesh with flipped normals has the benefit of potentially reducing draw calls as the mesh is only rendered once. There's basically three ways to do double sided.ġ.