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Mesh alpha acting like invisiprims

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Thank you!  This bug has been driving me crazy with a new project I'm working on.  I had multiple rigged meshes layered with all but one set to 100% transparency at a time but the invisible meshes occluded the visible one, however only meshes with an alpha were affected.  The developer viewer posted works as expected. 

A possibly related bug was also fixed where any rigged mesh with transparency would disappear when you turned on Lighting and Shadows.

Is there an ETA on when this fix might make it into the official viewer?

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Charlar, the only way you're going to be able to really squash both issues at once is to fix the alpha sorting glitch.

 

Yes, that one. Since I'm hearing that's something that's existed long before SL even came about, that's not in the cards, and thus what I have will be broken and can't be fixed.

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Tiberious Neruda wrote:

Charlar, the only way you're going to be able to really squash both issues at once is to fix the alpha sorting glitch.

 

Yes, 
that
 
one. Since I'm hearing that's something that's existed long before SL even came about, that's not in the cards, and thus what I have will be broken and can't be fixed.

Wait a few more years for hardware to catch up. Solutions (yes there are more than one) to alpha sorting have been around for a while (decades in some cases), however the amount of processing and memory they require is quite high and scales with the amount of alpha content visible (which is way too much in sl). The current best solution that I know of has unbounded memory requirements, it would need close to 500MB of vram to render the average forest sim in sl, that's just for sorting all the alpha fragments.

Many professionally made games are already using these solutions, but well, they have professional artist that know what they're doing or get fired if they don't. We don't have such luxuries in sl where any one can upload anything, thus we have to wait for hardware fast enough to handle our user made (amature) content.

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leliel Mirihi wrote:

Many professionally made games are already using these solutions, but well, they have professional artist that know what they're doing or get fired if they don't. We don't have such luxuries in sl where any one can upload anything, thus we have to wait for hardware fast enough to handle our user made (amature) content.

Or those professionals work with the issue rather than using real fixes. I'm not entirely sure, but in my experience SL does a pretty good job on alpha sorting when the objects aren't too close together. The problem occurs when you have (various sized) objects close together and/or intersecting. For example a big dome with an alpha channel will give issues with hair because the centerpoint of the dome is used for reference and it can be closer to the camera than the hair. Then the background will show. Or three planed trees where the centerpoint of all planes is in exactly the same place.

In games the camera position is very limited so the designer of the scene can avoid a lot of issues.

With mesh you can determine the alpha sorting, I think Drongle posted some good information about this, at least within an object. As I recall it and as I have seen it myself (I didn't really take a good look, let alone doing serious testing) All faces in a mesh behave the same way from any given angle. 3 planed mesh trees behave worse from some angles and better from others because of this.

I wouldn't wait for a solution made available by better hardware aswell. Even if the hardware is ten times as powerful, programs and users will stretch the limits again, so you'll have the same issue. So for SL it would take hardware that could handle the geometry of let's say 9 sims, with 15 000 prims in sight on all of them, all faces with unique 1024x1024 textures etc and then some power to spare for the alpha sorting. I'm afraid that will never happen... As you said, in any way not soon.

 

 

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Yes you're right that many games just work around it instead of solve it, it's a lot of extra work tho. The whole point of order independent transparency is it makes the problem a nonissue from the artist's point of view, they don't have to think about or even know about it. Maybe you're right that hardware will never be fast enough due to ever increasing demands, but we can dream can't we.

Maybe this year I'll take a crack at adding A-buffer support to the viewer. Of course once I see the performance in sl I'll probably run for the hills screaming. o.O

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I just tried a viewer with this fix in it, and I'm pleased to note my fears were unfounded.

The fix only takes effect when a face on the mesh is set to 100% transparency via either LSL or the Edit window. Until that point, even if set at 99%, the old behavior is preserved. This means that if you use a texture with alpha, it will still act like an invisiprim to 32-bit textures behind it, even if it's TEXTURE_TRANSPARENT, so keep that in mind.

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