DepthBuffer
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Below has not been tested properly, and may have mistakes
// //-- Stuff for reading depth buffer // //-- Reading depth buffer supported by: //-- NVidia - from GeForce 6 (2004) //-- Radeon - from 9500 (2002) //-- Intel - from G45 (2008) // //-- Sources: //-- http://obge.paradice-insight.us/wiki/Internals_%28Effects%29 //-- http://www.gamasutra.com/blogs/BranoKemen/20090812/2725/Logarithmic_Depth_Buffer.php //-- http://mynameismjp.wordpress.com/2009/05/05/reconstructing-position-from-depth-continued/ //-- //-- These two are set by MTA texture gDepthBuffer : DEPTHBUFFER; matrix gProjectionMainScene : PROJECTION_MAIN_SCENE; sampler SamplerDepth = sampler_state { Texture = (gDepthBuffer); AddressU = Clamp; AddressV = Clamp; }; //--------------------------------------------------------------------- // Structure of data sent to the pixel shader ( from the vertex shader ) //--------------------------------------------------------------------- struct PSInput { float4 Position : POSITION0; float2 TexCoord0 : TEXCOORD0; }; //----------------------------------------------------------------------------- //-- Get value from the depth buffer //-- Uses define set at compile time to handle RAWZ special case (which will use up a few more slots) //----------------------------------------------------------------------------- float FetchDepthBufferValue( float2 uv ) { float4 texel = tex2D(SamplerDepth, uv); #if IS_DEPTHBUFFER_RAWZ float3 rawval = floor(255.0 * texel.arg + 0.5); float3 valueScaler = float3(0.996093809371817670572857294849, 0.0038909914428586627756752238080039, 1.5199185323666651467481343000015e-5); return dot(rawval, valueScaler / 255.0); #else return texel.r; #endif } //----------------------------------------------------------------------------- //-- Use the last scene projecion matrix to linearize the depth value a bit more //----------------------------------------------------------------------------- float Linearize(float posZ) { return gProjectionMainScene[3][2] / (posZ - gProjectionMainScene[2][2]); } //----------------------------------------------------------------------------- //-- Name: PS_Example //-- Type: Pixel shader //-- Desc: Calculates the pixel color based on texture lookup and interpolated vertex color //----------------------------------------------------------------------------- float4 PS_Example( PSInput In ) : COLOR { float BufferValue = FetchDepthBufferValue( In.TexCoord0.xy ); float Depth = Linearize( BufferValue ); //-- Multiply Depth to get the spread you want Depth *= 0.1f; //-- Show depth as green float4 OutColor = 0; OutColor.g = Depth; OutColor.a = 1; return OutColor; } //----------------------------------------------------------------------------- //-- Techniques //----------------------------------------------------------------------------- // //-- Use any readable depthbuffer format // technique yes_effect { pass P0 { PixelShader = compile ps_2_0 PS_Example(); } } // //-- If no depthbuffer support, do nothing // technique no_effect { pass P0 { } }