Efficient shader for sky plane

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I am using a flat plane for my sky and have created the following shader for it. How can I have the sky render behind everything?

Setting ZTest to off seems to do the trick, but surely this is rather costly on the iPhone right?

I am after the fastest possible shader that shows a tiled texture on a plane.

 Shader "Sky/Backdrop" {
 
 Properties {
     _MainTex ("Base (RGB)", 2D) = "white" {}
 }
 
 SubShader {
     Tags { "Queue"="Background" }
     
     Lighting Off
     ZWrite Off
     
     Pass {
         SetTexture [_MainTex]
     }
 }
 
 }

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Answer by Jessy · Mar 28, 2012 at 02:04 PM

A fixed function shader is not going to yield the best performance/battery life. The background queue is not a good place for it. Reason being, the whole thing will need to be drawn, instead of just the visible pixels. You've got the right idea, but you need to figure out what will work for your scene. Putting it in the Geometry queue should yield the best performance, but changing to ZWrite Off will incur a performance hit. If you need that, move it into a later queue. But figure out why you need it. It's likely that your scene isn't set up optimally, if you can't have the background writing to the depth buffer.

http://unifycommunity.com/wiki/index.php?title=Texture_Only

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numberkruncher · Mar 28, 2012 at 04:18 PM 0

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Thanks Jessy, that makes a lot of sense. Thanks also for the shader, I haven't got around to learning GLSL yet so that is rather handy!

numberkruncher · Mar 28, 2012 at 05:23 PM 0

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@Jessy I have just compiled my project to iPhone and the sky texture doesn't appear to tile using your shader. Do you know why this might be?

Efficient shader for sky plane

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