Hi everyone,

I'm making changes to my deferred system. I want to delete the position texture (too much expensive GL_RGB32F) so in the light pass I have to reconstruct the pixel position from depth.

I tried for a few days without luke, so now I'm some how frustated.

What works (old position texture):

Geometry pass - Vertex:

Geometry pass - Fragment:Code :vsPosition = ( ModelViewMatrix * vec4(in_Position, 1.0) ).xyz; ... gl_Position = MVP * vec4(in_Position, 1.0);

This is how I store old pixel positions on geometry pass.Code :fsPosition = vsPosition;

So next is to figure how to get this without the texture. I tried MANY things that I found around the net (without luke...), what i have now is:

Light pass - fragment:

Code :vec2 calcTexCoord() { return gl_FragCoord.xy / ScreenSize; } vec3 positionFromDepth() { vec2 sp = calcTexCoord(); float depth = texture2D(Texture4, sp).x * 2.0 - 1.0; vec4 pos = InvProjectionMatrix * vec4( sp*2.0-1.0, depth, 1.0); return pos.xyz/pos.w; } vec3 computePhongPointLight() { vec3 color = vec3(0.0); vec2 texCoord = calcTexCoord(); //vec3 position = texture2D( Texture0, texCoord ).xyz; vec3 position = positionFromDepth(); vec3 difColor = texture2D( Texture1, texCoord ).xyz; vec3 specColor = texture2D( Texture2, texCoord ).xyz; vec3 normColor = texture2D( Texture3, texCoord ).xyz; vec3 lightDir = Light.position.xyz - position; vec3 lightDirNorm = normalize( lightDir ); float sDotN = max( dot(lightDirNorm, normColor), 0.0); float att = 1.0; float distSqr = dot(lightDir, lightDir); float invAtt = (Light.constantAtt + (Light.linearAtt*sqrt(distSqr)) + (Light.quadraticAtt*distSqr)); att = 0.0; if (invAtt != 0.0) att = 1.0/invAtt; vec3 diffuse = difColor.rgb * Light.diffuse * sDotN; vec3 ambient = difColor.rgb * Light.ambient; // Cheat here vec3 vertexToEye = normalize(position); vec3 r = normalize(reflect(lightDirNorm, normColor)); // SpecularPower vec3 specular = vec3(0.0); if ( sDotN > 0.0 ) { specular = Light.specular.rgb * specColor * pow( max( dot(vertexToEye, r), 0.0), 60.0 ); // Change specular here!!!! value 60 must be an uniform } return (diffuse + specular + ambient)*att; }

Where Texture0 is old position texture, Texture4 is depth texture, InvProjectionMatrix is the inverse projection matrix, and Light.position is computed as ViewMatrix * light_position.

I did some debug and I output the absolute diference:

Code :vec3 pos1 = positionFromDepth(); vec3 pos2 = texture2D(Texture0, calcTexCoord()).xyz; fragColor = vec4(abs(pos2.x-pos1.x), abs(pos2.y-pos1.y), abs(pos2.z-pos1.z), 1.);

The output is all black minus empty zones that are white.

I think it's space error, something like: light position in view space and pixel position is in other space so "vec3 lightDir = Light.position - position" give bad results. But I can't figure what's happening, and how to solve it...

I will really apreciate any help (cause I don't know what more to do), and I hope that someone with better math can help me

Sorry for my bad English and thanks in advance.