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LiamZander

Mesh flickering, need help!

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Hi again! 

Last time You've been really helpful, so I've decided to post with one more thing.

 

I'm having trouble with my meshes flicker out of blue while theyre close to each other, they keep overlapping...

example here: flickering 1.png

 

It shows up as there black spots.

However when I keep zooming away it keeps changing between being normal and showing these black spots, it keeps flickering. 

I've tried various LOD settings, uploading .jpg textures to make sure there's no alpha channel, changing blending mode to make sure theres no alpha...but it keeps happening. 

This is how it's supposed to look like: 

Flickering 2.png

 

 

Sadly nothing helps....

Did anyone experience that before? Is that an issue with model itself? 

I'll be thankful for any advice,

Liam

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This typically happens when meshes are intersecting each other or touching each other. In your case, make sure that the top cards are not actually touching the cards on the next layer down. It also happens on THIN meshes (like windows if they are too close to another surface or slightly touching.  It isn't an alpha issue as it happens with completely solid textures (even NO textures :D).  

 

 

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The flickering itself is unavoidable, except by structuring your meshes in such a way that there's sufficient gap between overlapping triangles. Its caused by the renderer trying to work out which triangle is in front when the distances are too small to calculate accurately.

http://en.wikipedia.org/wiki/Z-buffering

The black marks look like shadows being cast by the top cards, but the renderer is then getting confused as to which triangle is on top.

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I see... Thanks for reply. First thing I was experiencing with was making sure that these cards aren't touching each other... Then I tried making larger gap between them, but I have to move them really far away to make flickering go away. I can't move it too far or it will look terribly unnatural.

So I guess there's no simple solution to that? :/

Liam

 

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There is no simple solution, the phenomenon is called Z-Fighting. Two polygons fight for their position in a place called z-buffer. The larger the scene the worse the z-fighting gets. And as we know, SL scenes are large...

Usually a procedure called z-test returns almost randomly whatever polygon as the topmost.

One solution in your card stack might be to add some more geometry. Maybe twist the cards using a couple of extra edgeloops. (You know, old cards are kinda curved after they have been tortured by players :) ). That might add natural distance between polygons...

 

 

 

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Thanks for reply! I've been testing it for quite a while and I really don't get how it works. Sometimes it works fine couple times when im around it, and then when i relog it starts flickerng. Moreover, I've noteiced it on plenty objects it didn't happen before. At the same time all the people around me say they can't see any flickering. So i'm wondering if it's something individual? Is that because of that random alghoritm? I've tried numering layers of vertices so it renders them in proper order from top to bottom, but that didn't help at all.

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That sounds interesting, and the cause might be in your graphics settings. Does your graphics card have any advanced settings? The z-buffer thingie is usually implemented in graphics card and/or graphics driver software or firmware.

I know some graphics cards do have options to manipulate z-buffer size and handling, but mostly not...

 

 

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I'm not sure right now, maybe that's it. I never had trouble with my meshes and I've been doing similar works as well...this just happened recently. So I'm wondering now.

I know that in past ATI cards ( I have one) have had trouble with rendering with second life, with  newer drivers it got better at some point, maybe they messed up something as well ( I know there has been a lot trouble with OpenGL).

I made my family and my girlfiend today to relog multiple times and tell me if they see any flickering, but they didn't see anything. ..they thought I'm going crazy at some point :P  But then I saw that meshes that weren't having this issue before now do...and some are perfectly fine.

I have no clue what the problem is now.  I even see stuff flicker sometimes when face is facing same direction, but its far from another face facing same way if I zoom out enough ( and once again, it's not LOD issue because I tested it with max LOD).

Changing graphics settings, windlights and stuff doesn't change anything either.

 

I think I will just carry on and see if that occurs more in future...or if anyone reports me flickering of my stuff. It might be just my computer.

Liam

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i think the problem is that mesh in sl sometimes gets stuck in a lower LOD. It seems to happen randomly, if you right click the item like you intend to edit it it mostly reloads to the full LOD and the flickering is gone.

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