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#236698 - 04/05/08 06:05 PM Screen-Space Ambient Occlusion
Leadwerks Regular Contributor Registered: 03/11/07 Posts: 410 Loc: California	The results of this effect are pretty awesome, and it seems like a self-contained post-processing effect. Has anyone done any work with this, or are there any GLSL examples around?: http://www.gamedev.net/community/forums/topic.asp?topic_id=463075
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#236700 - 04/05/08 06:34 PM Re: Screen-Space Ambient Occlusion [Re: Leadwerks]
sqrt[-1] Frequent Contributor Registered: 06/05/02 Posts: 910 Loc: Australia	Also read this for lots of useful links: http://levelofdetail.wordpress.com/2008/02/10/2007-the-year-ssao-broke/ You can have a look at the Crysis Cg shader source if you have the game (or demo)
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#236702 - 04/05/08 11:32 PM Re: Screen-Space Ambient Occlusion [Re: sqrt[-1]]
havokentity Newbie Registered: 10/31/05 Posts: 26 Loc: Chennai, Tamil Nadu, India	Yes, I've done some experimentation. I've got good results that work over 60 fps on a 8600 GT but with ugly outlines, so I stuck with the standard way of doing it. In my first experiment, I tried it with a gaussian blurred texture, taken from the bloom pass. If anyone has any success with a gaussian blurred texture without outlines of objects, please tell me how you removed the artifacts. I've posted a small post about SSAO on my blog: http://rajeshdmonte.blogspot.com/2008/04/experiments-with-ssao-screen-space.html _________________________ -Rajesh http://rajeshdmonte.blogspot.com/
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#236718 - 04/06/08 01:42 PM Re: Screen-Space Ambient Occlusion [Re: havokentity]
elvis Newbie Registered: 03/11/08 Posts: 7	I've been made an implementation about this technique. check out my blog: http://gamedusa.blogspot.com For some GLSL code you can go to RGBA homepage of Iñigo Quilez.
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#236719 - 04/06/08 01:43 PM Re: Screen-Space Ambient Occlusion [Re: havokentity]
elvis Newbie Registered: 03/11/08 Posts: 7	I've been made an implementation about this technique. check out my blog: http://gamedusa.blogspot.com For some GLSL code you can go to RGBA homepage of Iñigo Quilez.
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#236738 - 04/07/08 02:25 PM Re: Screen-Space Ambient Occlusion [Re: elvis]
Leadwerks Regular Contributor Registered: 03/11/07 Posts: 410 Loc: California	Iñigo's code looks good, but he uses an extra render target to output a linear depth, which I think is completely unnecessary. I want to write a shader that will just work on any generic depth buffer...then people can just plug it into their engine, and BOOM! instant real-time GI (sort of). $;\)$ Edited by Leadwerks (04/07/08 02:26 PM)
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#236743 - 04/07/08 02:45 PM Re: Screen-Space Ambient Occlusion [Re: Leadwerks]
Leadwerks Regular Contributor Registered: 03/11/07 Posts: 410 Loc: California	Well, here's code to convert the exponential depth to a linear value (thanks Humus): // Convert exponential depth value to linear depth float f=1000.0; float n = 0.1; float z = (2 * n) / (f + n - texture2D( texture0, texCoord ).x * (f - n)); I am afraid I do not understand the rest of his shader...so it's either a matter of copying everything exactly, or implementing my own method from scratch. http://rgba.scenesp.org/iq/computer/articles/ssao/ssao.htm Edited by Leadwerks (04/07/08 02:46 PM)
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#236746 - 04/07/08 04:11 PM

Re: Screen-Space Ambient Occlusion [Re: Leadwerks]

Leadwerks Offline

Regular Contributor

Registered: 03/11/07
Posts: 410
Loc: California

Well, right now this is basically just a soft outline shader:

Code:

uniform sampler2D texture0;
uniform vec2 camerarange;

varying vec2 texCoord;


float readDepth( in vec2 coord ) {
	return (2.0 * camerarange.x) / (camerarange.y + camerarange.x - texture2D( texture0, coord ).x * (camerarange.y - camerarange.x));	
}


void main(void)
{	
	float depth = readDepth( texCoord );
	float d;
	
	float pw = 1.0 / 800.0 * 2.0;
	float ph = 1.0 / 600.0 * 2.0;

	float ao = 0.0;
	
	float aoMultiplier=1000.0;

	float depthTolerance = 0.001;
	
	d=readDepth( vec2(texCoord.x+pw,texCoord.y+ph));
	ao+=max(0.0,d-depth-depthTolerance) * aoMultiplier;

	d=readDepth( vec2(texCoord.x-pw,texCoord.y+ph));
	ao+=max(0.0,d-depth-depthTolerance) * aoMultiplier;

	d=readDepth( vec2(texCoord.x+pw,texCoord.y-ph));
	ao+=max(0.0,d-depth-depthTolerance) * aoMultiplier;

	d=readDepth( vec2(texCoord.x-pw,texCoord.y-ph));
	ao+=max(0.0,d-depth-depthTolerance) * aoMultiplier;
	
	ao/=4.0;
	ao=min(ao,0.25);
	
	gl_FragColor = vec4(1.0-ao);
}

Here it is multiplied by 0.5. The problem is that in very corners, the sample right next to one surface is the same depth, so it doesn't detect a difference, and it makes the corner bright.

Edited by Leadwerks (04/07/08 04:46 PM)

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#236751 - 04/07/08 08:21 PM

Re: Screen-Space Ambient Occlusion [Re: Leadwerks]

Leadwerks Offline

Regular Contributor

Registered: 03/11/07
Posts: 410
Loc: California

Here is it, the shader you have been waiting for, perhaps dreaming of.

vert:

Code:

varying vec2 texCoord;

void main(void) {
	gl_Position = ftransform();
	texCoord=gl_MultiTexCoord0.xy;
	gl_FrontColor = gl_Color;
}

frag:

Code:

uniform sampler2D texture0;
uniform sampler2D texture1;

uniform vec2 camerarange;
uniform vec2 screensize;

varying vec2 texCoord;


float readDepth( in vec2 coord ) {
	return (2.0 * camerarange.x) / (camerarange.y + camerarange.x - texture2D( texture0, coord ).x * (camerarange.y - camerarange.x));	
}


void main(void)
{	
	float depth = readDepth( texCoord );
	float d;
	
	float pw = 1.0 / screensize.x;
	float ph = 1.0 / screensize.y;

	float aoCap = 1.0;

	float ao = 0.0;
	
	float aoMultiplier=1000.0;

	float depthTolerance = 0.0001;
	
	d=readDepth( vec2(texCoord.x+pw,texCoord.y+ph));
	ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

	d=readDepth( vec2(texCoord.x-pw,texCoord.y+ph));
	ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

	d=readDepth( vec2(texCoord.x+pw,texCoord.y-ph));
	ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

	d=readDepth( vec2(texCoord.x-pw,texCoord.y-ph));
	ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);
	
	pw*=2.0;
	ph*=2.0;
	aoMultiplier/=2.0;

	d=readDepth( vec2(texCoord.x+pw,texCoord.y+ph));
	ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

	d=readDepth( vec2(texCoord.x-pw,texCoord.y+ph));
	ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

	d=readDepth( vec2(texCoord.x+pw,texCoord.y-ph));
	ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

	d=readDepth( vec2(texCoord.x-pw,texCoord.y-ph));
	ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

	pw*=2.0;
	ph*=2.0;
	aoMultiplier/=2.0;

	d=readDepth( vec2(texCoord.x+pw,texCoord.y+ph));
	ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

	d=readDepth( vec2(texCoord.x-pw,texCoord.y+ph));
	ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

	d=readDepth( vec2(texCoord.x+pw,texCoord.y-ph));
	ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

	d=readDepth( vec2(texCoord.x-pw,texCoord.y-ph));
	ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

	pw*=2.0;
	ph*=2.0;
	aoMultiplier/=2.0;

	d=readDepth( vec2(texCoord.x+pw,texCoord.y+ph));
	ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

	d=readDepth( vec2(texCoord.x-pw,texCoord.y+ph));
	ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

	d=readDepth( vec2(texCoord.x+pw,texCoord.y-ph));
	ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

	d=readDepth( vec2(texCoord.x-pw,texCoord.y-ph));
	ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

	ao/=16.0;
	
	gl_FragColor = vec4(1.0-ao) * texture2D(texture1,texCoord);
}

Uniforms:
vec2 camerarange - near and far camera range
vec2 screensize - screen width and height

Edited by Leadwerks (04/07/08 08:22 PM)

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#236786 - 04/08/08 10:55 AM Re: Screen-Space Ambient Occlusion [Re: Leadwerks]
Vexator Regular Contributor Registered: 07/11/05 Posts: 274 Loc: Germany	mh all i get are black outlines around my meshes. how do you render texture0? i pass -(gl_ModelViewMatrix*gl_Vertex) to the fragment shader and output its length. what's texture1 supposed to be? the original scene? what about the normal map Quilez uses? do i need to perform a blur pass afterwards? _________________________ www.wunderwerk.blogspot.com
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