I'm trying for a few days removing my position texture from my deferred system. To achive this I have to reconstruct pixel position from depth value.

I spend some days now (many houres) tring to solve the problem without luck, so I'm somehow frustated.

Let's see if someone with better math can help me

First how i fill my old position texture (geometry pass). [With this texture the lighting works fine.]

Geometry pass - Vertex: vsPosition = ( ModelViewMatrix * vec4(in_Position, 1.0) ).xyz; Geometry pass - Fragment: fsPosition = vsPosition

Where ModelViewMatrix is ViewMatrix * ModelMatrix.

From here all work, and accessing pixel position in the light pass is trivial.The problem occurs when I try to compute pixel position with depth value.

I tried many things (many...), and what I have at the moment is:

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; }

Where InvProjectionMatrix is the inverse of the projection matrix, and Texture4 is depth texture.

The strange thing is that if I output the absolute diference from both (using texture and using depth), i see black output (no diferences).

Following code outputs black screen: (Texture0 is position texture)

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.);

Here is my point light calculation: (With pixel position from depth doesn't work)

uniform struct { vec3 diffuse; vec3 specular; vec3 ambient; float constantAtt; float linearAtt; float quadraticAtt; float spotInnerCutOff; float spotOuterCutOff; float spotFallOff; vec3 position; // For Point light. Computed as ViewMatrix * light_position vec3 direction; // For Spot and Directional lights int type; // 0-> Point, 1-> Spot, 2-> Directional } Light; ... 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; }

I will apraciate any help, so feel free to answer

Sorry for my bad English and thanks in advance.

**Edited by junkyska, 27 November 2012 - 02:07 PM.**