Mysterious black rendered pixels, but not coplanar geometry?

[crazy homeless guy]

I have been having this problem recently... I am not sure if it has to do with my settings, or the fact that the model originated in Revit.
For some reason I am getting black lines in fine details of me Revit model. I can usually crank my settings, and get rid of them, but that solution does not always work.

I have checked, and there is not coplanar faces.

I usually try and solve the problem by cranking up the Clr thresh, the Nrm thresh, and the Dist thresh in the Irradiance map rollout. This rendering was done with them all set at 0.6, but I still got the problems of the black lines.

I also have my secondary rays bias set to 0.02.

This particular rendering is being rendered at 2000 pixels wide, and the GI passes were calculated at that resolution.

[claude_tnt]

check the smoothing.. somehow or the other some revit faces inadvertantly gets smoothed
claude

[crazy homeless guy]

check the smoothing.. somehow or the other some revit faces inadvertantly gets smoothed
claude

Is this smoothing as a modifer? I tried rendering with a modifer added, and both enabled and not, the results were nearly identical.

If this is how 3dsMax re-evauluates smoothing groups on import via FBX, then it is to late. I have modified the geometry to much to go back.

[Da_elf]

Color threshold (Clr thresh) - this parameter controls how sensitive the irradiance map algorithm is to changes in indirect lighting. Larger values mean less sensitivity; smaller values make the irradiance map more sensitive to light changes (thus producing higher quality images).



Normal threshold (Nrm thresh) - this parameter controls how sensitive the irradiance map is to changes in surface normals and small surface details. Larger values mean less sensitivity; smaller values make the irradiance map more sensitive to surface curvature and small details


from the manual. seems your going in the right direction for dist thresh but the wrong direction for clr and nrm

[skogskalle]

Throw an edit poly on the object, select all polygons, scroll down to smoothing groups and choose "clear all". (will fuck up rounded objects since youll see all the faces instead of a smooth surface, but should work in your case since your object seems to be all flat surfaces and sharp edges anyways)

/k

[crazy homeless guy]

seems your going in the right direction for dist thresh but the wrong direction for clr and nrm

Ahhh. I have only worked witht he distance threshold in the past. I assumed that the Color, and Normal worked in a similar fashion. You know what they say about people who assume.

[crazy homeless guy]

Throw an edit poly on the object, select all polygons, scroll down to smoothing groups and choose "clear all". (will fuck up rounded objects since youll see all the faces instead of a smooth surface, but should work in your case since your object seems to be all flat surfaces and sharp edges anyways)

/k

At first I thought this would woirk, but in the end I still had the odd spots.

One of the wierd things is that they are not consistent. If I change resolution, or move the camera, the location of the black spots will move on that object. This is why I was assuming it had something to do with sampling at the GI level, or possible the DMC/AA level. I just can't seem to figure out the solution.

[crazy homeless guy]

Also, I realized late last night that my problem is not limited to Revit geometry. The specific piece I have circled in my post was constructed in 3dsMax.

[crazy homeless guy]

Ok. I solved the problem. Well... not so much solved it as got it to not do it anymore. I set the rendering engine to scanline, rendered, and then set it back to Vray, and re enabled all my custom settings. No black dots.

So, .....whatever the problem was, it was fixed by resetting Vray.

[beestee]

I think this is caused by the "check sample visibility" setting in the IRR map. It needs to be off to avoid these errors.

Something Mr. Prevost from Solidrocks figured out a while back.

EDIT: Back when I ran into it at first, I just ended up supersampling the crud out of my IRR map to get it to go away...of course this solution was far from elegant due to the skyrocketing render times. I toyed with the CLR and NRM thresholds running up and down the specturm looking for the perfect settings, and I ran into the same issue as you, where it would be good in one area but mess up in another. Annoying little bug this one!

[crazy homeless guy]

That might definitely be it. The image is rendering, so I am not going to check it now, but I typically turn on check sample visibility. I thought that was a good thing. When I reset the scene, I don't think I turned that on.

[beestee]

The VRay default for the setting is off, so resetting VRay would definitely fix it.