SSAO and skybox artifact

Jake S. Del Mastro · 2012-12-08T19:49:26

I'm running into an ugly artifact with my SSAO where when geometry against the skybox is being occluded by the skybox and vice versa, I was able to fix the skybox being occluded by simply skipping the ssao calculation as soon as I know that the pixel is a skybox. I still have the problem with the skybox occluding my geometry creating an ugly dotted line, the skybox is black in the gbuffer and at depth 1.0 but after trying uselessly to skip sampling the skybox using a step function, I decided to ask here. Anyway here is my glsl shader code based heavily on code from here: uniform sampler2D depth_texture; uniform sampler2D color_texture; uniform sampler2D normal_texture; uniform float scr_w; uniform float scr_h; uniform vec3 pSphere[10] = vec3[]( vec3(-0.010735935, 0.01647018, 0.0062425877), vec3(-0.06533369, 0.3647007, -0.13746321), vec3(-0.6539235, -0.016726388, -0.53000957), vec3(0.40958285, 0.0052428036, -0.5591124), vec3(-0.1465366, 0.09899267, 0.15571679), vec3(-0.44122112, -0.5458797, 0.04912532), vec3(0.03755566, -0.10961345, -0.33040273), vec3(0.019100213, 0.29652783, 0.066237666), vec3(0.8765323, 0.011236004, 0.28265962), vec3(0.29264435, -0.40794238, 0.15964167)); varying vec2 vTexCoord; #define STRENGTH 0.09 #define FALLOFF 0.0 //0.00002 #define RAD 0.006 #define SAMPLES 10 #define INVSAMPLES 1.0/SAMPLES vec4 height_normal(in vec2 texcoord) { vec4 normaltexel; normaltexel.rgb = (texture2D(normal_texture, texcoord).xyz * 2.0) - vec3(1.0); normaltexel.a = texture2D(depth_texture, texcoord).x; return normaltexel; } void main(void) { // get a random normal vec3 fres = normalize((texture2D(color_texture, vTexCoord * (scr_w / 64)).xyz * 2.0) - vec3(1.0)); //grab depth and a normal vector vec4 currentPixelSample = height_normal(vTexCoord); vec3 samplepos = vec3(vTexCoord.xy, currentPixelSample.a); float blacklevel = 0.0; float depthDiff; vec4 occluderFragment; vec3 ray; if(length(currentPixelSample.xyz) <= 1.0) //dont calculate ssao because the pixel is in skybox { for(int i = 0; i < SAMPLES; ++i) { // trace a ray from a random normal to a random position ray = (RAD / samplepos.z) * reflect(pSphere, fres); occluderFragment = height_normal(samplepos.xy + (sign(dot(ray, currentPixelSample.xyz)) * ray.xy)); //get the position of the occluder depthDiff = samplepos.z - occluderFragment.a; blacklevel += step(FALLOFF, depthDiff) * (1.0 - dot(currentPixelSample.xyz, occluderFragment.xyz)) * (1.0 - smoothstep(FALLOFF, STRENGTH, depthDiff)); } } // output the result gl_FragColor = vec4(vec3(1.0 - (blacklevel * INVSAMPLES)), 1.0); } attached is a picture of my problem the the offending pixels circled. Anyone know how to fix this?

Graphics and GPU Programming Programming

Started by ic0de December 06, 2012 03:59 AM

10 comments, last by MJP 11 years, 4 months ago

CryZe

773

December 08, 2012 01:04 PM

[quote name='CryZe' timestamp='1354868138' post='5008035']
A warp consists of either 16 or 32 threads grouped together.

I think you mean "32 or 64"

[/quote]

I thought a Wavefront on AMDs architecture consists of 16 execution units. Or am I wrong? (I just used warp as a general term, because I like it more

)

MJP

20,295

December 08, 2012 07:49 PM

[quote name='MJP' timestamp='1354934346' post='5008334']
[quote name='CryZe' timestamp='1354868138' post='5008035']
A warp consists of either 16 or 32 threads grouped together.

I think you mean "32 or 64"

[/quote]

I thought a Wavefront on AMDs architecture consists of 16 execution units. Or am I wrong? (I just used warp as a general term, because I like it more

)
[/quote]

Nah there's 64 threads in a wavefront. In their latest architecture (GCN) the SIMDs are 16-wide, but they execute each instruction 4 times to complete it for the entire wavefront (so a single-cycle instruction actually takes 4 cycles to execute).

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