Blend 2 Textures by Lightmap Alpha

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Revision as of 22:19, 12 November 2009 by Jessy (Talk | contribs)

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Author: Jessy

Description

A textured quad that uses this shader.

This shader blends between two tiling textures based on a greyscale "splatmap", and uses a lightmap instead of real-time lighting.

Usage

In your modeling app, you create two UV maps - one for Texture 1 and Texture 2, and another for the lightmap and splatmap. The idea is that you will either extend the UVs of the model outside the 0-1 range, overlap them, or both, in the first map, and not do any of that in the second - standard lightmapping practice. By default, this means that your two main textures will tile at the same "rate", but you can use the Offset and/or Tiling controls in the Material, if you think it will add visual interest.

The splatmap is stored in the alpha channel of the lightmap. The two textures mix as if, in Photoshop, you had Texture 1 in a layer above Texture 2, and Texture 1 used the splatmap as a layer mask. i.e. white = Texture 1, black = Texture 2. In my usage so far, I've found that it's important to have the lightmap/splatmap be at a high resolution, to preserve the shape of fine splat details, but that it's okay to use PVRTC 2 bpp compression, as the color detail is mainly coming from Texture 1 and Texture 2.


Click here for a zip file that includes this shader.

ShaderLab - Blend 2 Textures by Lightmap Alpha.shader

<shaderlab>Shader "Blend 2 Textures by Lightmap Alpha" {


Properties { _MainTex ("Texture 1 (RGB)", 2D) = "" _Texture2 ("Texture 2 (RGB)", 2D) = "" _LightMap ("Lightmap (A = Splat)", 2D) = "" }

// iPhone 3GS and later SubShader { Pass { BindChannels { Bind "Vertex", vertex

// 1st UV - tiling textures Bind "texcoord", texcoord0 Bind "texcoord", texcoord2

// 2nd UV - lightmap and splatmap Bind "texcoord1", texcoord1 Bind "texcoord1", texcoord3 }

// tile Texture 2 SetTexture [_Texture2]

// put the splat map into the alpha channel SetTexture [_LightMap] { combine previous, texture }

// tile Texture 1 and combine it with Texture 2 based on the splat map SetTexture [_MainTex] { combine texture lerp(previous) previous }

// apply the lightmap SetTexture [_LightMap] { combine previous * texture } } }

// pre-3GS devices, including the September 2009 8GB iPod touch SubShader { Pass { BindChannels { Bind "Vertex", vertex Bind "texcoord", texcoord0 Bind "texcoord1", texcoord1 }

// tile Texture 2 SetTexture [_Texture2]

// apply the lightmap to Texture 2 SetTexture [_LightMap] { combine previous * texture } }

Pass { Blend SrcAlpha OneMinusSrcAlpha

BindChannels { Bind "Vertex", vertex Bind "texcoord", texcoord0 Bind "texcoord1", texcoord1 }

// tile Texture 1 SetTexture [_MainTex]

// apply the lightmap to Texture 1 // and blend in the result, using the splat map SetTexture [_LightMap] { combine previous * texture, texture } } }


}</shaderlab>

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