3 replies to this topic

[JPulham]

How do I get the scene depth into a texture using GLSL? I've tried using a varying 'veiwVec' and dividing by far clip plane and I've tried gl_FragCoord.z, but no matter what I seem to get 'banding' or a plain white screen. I have a A8R8G8B8 texture that I'm encoding the float value to. cheers.

[__sprite]

If my somewhat messily scribbled notes from the orange book are correct, you want something like this:

// VERTEX
uniform vec3 CamPos, CamDir;
uniform float DepthNear, DepthFar;

varying float CameraDepth;

...
    vec3 offset = (gl_Vertex.xyz / gl_Vertex.w) - CamPos;
    float z = -dot(offset, CamDir);
    CameraDepth = (z - DepthNear) / (DepthFar - DepthNear);
...

// FRAGMENT
varying float CameraDepth;

...

    gl_FragColor.xyz = vec3(CameraDepth);
    // Or whatever you want exactly here...
    gl_FragColor.w = 1.0;
...

[edit:] Oh, just read your post more carefully. How are you encoding the float value? [/edit]

[JPulham]

I am encoding to float<->RGBA8 using the code in this topic:
http://www.gamedev.net/community/forums/topic.asp?whichpage=1&pagesize=25&topic_id=463075
I think its 15th down, by Ysaneya.

/// Packing a [0-1] float value into a 4D vector where each component will be a 8-bits integer
vec4 packFloatToVec4i(const float value)
{
	const vec4 bitSh = vec4(256.0 * 256.0 * 256.0, 256.0 * 256.0, 256.0, 1.0);
	const vec4 bitMsk = vec4(0.0, 1.0 / 256.0, 1.0 / 256.0, 1.0 / 256.0);
	vec4 res = fract(value * bitSh);
	res -= res.xxyz * bitMsk;
	return res;
}

/// Unpacking a [0-1] float value from a 4D vector where each component was a 8-bits integer
float unpackFloatFromVec4i(const vec4 value)
{
	const vec4 bitSh = vec4(1.0 / (256.0 * 256.0 * 256.0), 1.0 / (256.0 * 256.0), 1.0 / 256.0, 1.0);
	return(dot(value, bitSh));
}

I can't test this right now as I'm am at school at the mo.. but thanks for the reply anyway

[JPulham]

I've tested it now and it does work :D
thanks for your help