I/we need a solution (workaround) for the evil black glass!

Heavily Tessellated · Post by **Heavily Tessellated** » Sat Sep 08, 2007 11:47 am

The first person that says "your normals are reversed" or "you need to turn smoothing off" gets his dad-burned head blasted off!

Obviously light is some complex sh*t. But for me just trying to render a physically accurate light bulb, or anything where light sources exist behind glass is an exercise in RAGE control.

So yea making a correctly illuminating frosted light bulb is bad enough at 250us/sample, but to then eat up 1+M faces and another 20+ minutes on startup because you have to tessellate it to death to get a smooth curved surface with no face smoothing... oops rage control lost! ARGH!!

What are we going to do... or more accurately, what are we going to force someone else do... about it?

zsouthboy · Post by **zsouthboy** » Sat Sep 08, 2007 12:36 pm

....

Uh.

WTF?

http://zsouthboy.com//displayimage.php?pos=-88

No 1+ M faces, no insane tesselation.

Normal smoothing, and edgesplit modifier in blender.

Post by **OnoSendai** » Sat Sep 08, 2007 7:18 pm

Heavily Tessellated wrote:The first person that says "your normals are reversed" or "you need to turn smoothing off" gets his dad-burned head blasted off!

Obviously light is some complex sh*t. But for me just trying to render a physically accurate light bulb, or anything where light sources exist behind glass is an exercise in RAGE control.

So yea making a correctly illuminating frosted light bulb is bad enough at 250us/sample, but to then eat up 1+M faces and another 20+ minutes on startup because you have to tessellate it to death to get a smooth curved surface with no face smoothing... oops rage control lost! ARGH!!

What are we going to do... or more accurately, what are we going to force someone else do... about it?

Can you be more specific about the exact problem please, perhaps you could post some example images?

Kram1032 · Post by **Kram1032** » Sat Sep 08, 2007 8:38 pm

@ zsouthboy: cool bulb

but I think, he talked about a white ("frosted") bulb...

maybe, glossy transparent with low exponent problems?

Zom-B · Post by **Zom-B** » Sat Sep 08, 2007 10:32 pm

Kram1032 wrote:@ zsouthboy: cool bulb but I think, he talked about a white ("frosted") bulb...

maybe, glossy transparent with low exponent problems?

yep.... the only Problem with "black glass" I know seems to appear for glossy transparent mats... here an example (grey one):

suvakas · Post by **suvakas** » Sat Sep 08, 2007 11:04 pm

hmm.. a light bulb.. i never want to go back to that thing again..at least never with Indigo

God knows how many times I've tried to create something similar like on zsouthboy's image, but I still nothing. I cant get the light to shine through the glass.

Kram1032 · Post by **Kram1032** » Sat Sep 08, 2007 11:57 pm

@ zsouthboy - what about sharing it, so that all the ppl, who don't know, what they did wrong, find it out?

The "They have the power" render also worked correctly...

Heavily Tessellated · Post by **Heavily Tessellated** » Sun Sep 09, 2007 10:53 am

That's a nice bulb example. But - How does it look off-axis and wide-angle lens, contained in a box, and without being lit by any scene meshlights, only the "filament" emitter(s)? Looks like pretty thick glass, I'm guessing you'd find black too @ IoR 1.5ish.

What's killing me currently is over in the Blender subforum. A Galilean thermometer. I can never get to see through all the various translucencies (playing with precedence until I want to just reformat my hd and play solitare) but the only time it looks right when backlit is turning all the glass bulbs to solid faces... then of course they reflect angularly and wrong. But without this, the curve edges always get black...

Ah well. Don't sweat it. I post when I'm frustrated.

CoolColJ · Post by **CoolColJ** » Sun Sep 09, 2007 1:25 pm

it could be a shading angle error from the blender exporter

yeah its's a pain, I get this issue with trying to create nice water with geometry in Skinidgo too

Probably easier to use a bump map in my case....

Tys · Post by **Tys** » Mon Sep 10, 2007 12:36 am

It's a bit fake maybe, but I used a transparent diffuse, and it works quite well, see the lampshade.. (idea for the room shamelessly stolen from -- eh, I can't find the originating image anymore, take credit, everyone;))
I did too try to get it working with sss materials, results see below;p

5OnIt · Post by **5OnIt** » Fri Sep 21, 2007 6:17 am

No blacks here that I can tell...

Kram1032 · Post by **Kram1032** » Fri Sep 21, 2007 6:20 am

it's quite strange... some have troubles, some don't....
about the lampshade: it needs far longer to render, I bet, but the SSSversion looks best

DaveC · Post by **DaveC** » Fri Sep 21, 2007 6:28 am

I find a lot of problems are solved by applying any scaling that was performed on the objects in question. And making sure that absorption on clear glass is at zero.

Heavily Tessellated · Post by **Heavily Tessellated** » Fri Sep 21, 2007 6:58 am

Well, no glass is zero absorption... flint glass, crown glass, even crystal... there's so many ingredients that unless you're an incredibly rich optics maker, it's not gonna be 96% clear much less 100%. Kinda like that light filament. Cool render, but, pure white?

Well, in my case nearly every problem can be traced to Blender and autosmoothing. They are all facenormal errors. The renderer is doing exactly what it's being told, however wrong. A couple of them are precedence related, until nik explained that to make it behave you have to intentionally overlap the meshes, not butt them up 0.00001 close.

Kram1032 · Post by **Kram1032** » Fri Sep 21, 2007 7:18 am

why do you still use autosmoothing, then?

you can try to combine it with edgesplit... but never use it alone^^
I wont use it at all...

I/we need a solution (workaround) for the evil black glass!

I/we need a solution (workaround) for the evil black glass!

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