Texture on a single plane: How to deal with back-face culling?

I'm made a very simple plant with just textures on simple planes, so I can save on performance. But back-face culling kinda ruins it. How to I counter this?

 

You could use a shader which doesn't use backface culling, but that's not always a good solution. I think it's more common to copy the model in your modelling software and simply flip the directions. This way you'd have more polygons in your scene, but it's most-likely the better solution as far as i know as only one of both sides can be visible at once anyways.

 

Are you talking about flipping the normals?
--------------EDIT--------------
Nevermind, found a way.

 

Yes, the normals.

Any other way that you found out?

 

Flipping the normals would still keep a single normal. Extruding the vertices creates two normals, at the expense of a couple of tris.

 

Extruding also adds polygons between both sides, which are most-likely pretty small in your case and cannot be seen by the user, but they're still there for the engine.

What i meant is duplicating your leaves, keep one as it was before and flip the other one. This way you don't have the extra polygons connecting both sides with each other. That should work, i've already used that method in blender and exported everything to Unity.

 

Extruding slightly is the way I would go... simply flipping and keeping the two models at the same location may cause z-fighting issues as you'll have two polys at the same location... although if they're backface culled it may not. Only way to know is to try it. The other benefit you get of extrusion is when viewing from a grazing angle or a distance from an angle it would probably look more accurate.

 

Back face culling is a rendering optimization. If you don't want it, just turn it off by adding two words; "Cull Off" to your shader.

Making duplicate polygons with reversed vertex normals is a waste of processing power for unnecessary culling calculations and waste of memory and disk space to store unnecessarily doubled mesh data.

 

That's true. However, if i'm not mistaken there's still the problem with incorrect lighting then. It rather depends on the situation.

 

Correct, using "cull off" results in incorrect lighting on the opposite side. While occasionally this can actually be what you want, in most cases you should just duplicate and flip normals (don't offset, there's no z-fighting since you can only ever see one side or the other)...it's not like GPUs have difficulty rendering polygons.

That won't necessarily save on performance; there's a reason Unity Pro has the option to have tight-fit mesh sprites rather than quads. If you have large empty areas, the GPU still has to render all those transparent pixels, so having more complex meshes that better fit the texture can be faster even though there are more polygons.

--Eric

 

If lighting is a consideration then you are right. Actually lighting problem can be solved with a two-pass shader, but having a second pass most probably makes things less efficient then having duplicate faces.

 

I see, but wouldn't occlusion culling fix that problem?