Artifacts with rendered glass

sk2k · Post by **sk2k** » Tue Sep 25, 2007 11:32 pm

Hi,

i exported a scene from blender with blendigo. The glass ist subdivided and smoothed. The glass looks ok but not the shadows/caustics. I marked the areas where it looks odd.

Anyone knows what's maybe wrong here?

MfG
sk2k

SmartDen · Post by **SmartDen** » Tue Sep 25, 2007 11:44 pm

share your blender file please

sk2k · Post by **sk2k** » Wed Sep 26, 2007 2:55 am

Hi,

i attached the scene file. Maybe it's my fault somewhere because i never used Blender and Indigo extensively before.

MfG
sk2k

Kram1032 · Post by **Kram1032** » Wed Sep 26, 2007 3:51 am

looks like smoothing errors....

Kram1032 · Post by **Kram1032** » Wed Sep 26, 2007 4:13 am

ok... I think, I can see it...
the surface isn't perfectly round... I think....
it ripples.
extremely slightly, but it does.

Heavily Tessellated · Post by **Heavily Tessellated** » Wed Sep 26, 2007 5:22 am

Hmm, I see face banding in the lower left circle you drew - are the faces set solid? If that's the case I have no idea what's going wrong. If it is a smoothing error, let me tell you, me and glass and autosmoothing have had a tough time with Indigo. I highly suggest using the EdgeSplit modifier. (thanks to Big Fan) There are smoothing errors that pop up after I think 25 degrees, so try it set to 25.

There's a thread I started last week like What IS it with me and glass? just below this one, see if following that gives you any insights.

One more thing, Indigo is more physically tied than blender. So if you're working with default blender primitives, you might end up with a glass that's 10 meters tall and 3 meters in diameter - this might account for the optic lens caustics; the walls would be a foot thick in Indigo space. (if this is the case, you can scale the models down, or use the world scale value in Blendigo to export it smaller.)

Kram1032 · Post by **Kram1032** » Wed Sep 26, 2007 6:00 am

I checked the scene, h.t.

It's a well-smoothed glass with smoothing turned on, no need for edge-splitting and auto-smoothing turned off.
But I can see in the "Solid" shader, that the rounding isn't perfect... it's slightly waved...
and then, besides that, I dunno, if it's supposed to be, or not, but it's slightly squared - kinda looks like a glass, that was made by extrude+scale the default cube and subdividing it a few times (subdiv wont give perfect round stuff, but an extremely smoothed square-like shape

)
- if it was done, that way, it doesn't explain the slightly wavy pattern, though...

joegiampaoli · Post by **joegiampaoli** » Wed Sep 26, 2007 6:41 am

Hmmm it does look like smoothing errors, but if you see the glass where the reflection is there is no facets there, maybe something that light amplifies as it goes through the glass and shows it on the ground surface, maybe very subdivided facets that the naked eye can't see

sk2k · Post by **sk2k** » Wed Sep 26, 2007 8:01 am

@heavy
Thanks, i will read your thread and try the edge split modifier.

@kram
You are correct. It's a extruded, scaled, subdivide ordinary cube.

Btw. some days ago i imported a glass (.obj format, modelled in MoI) into Blender and the resulting glass in Indigo was worser then the glass i modelled now. I tried smoothing, sudividing, etc. nothing helped. The faces were clearly visible on the glass.

MfG
sk2k

Kram1032 · Post by **Kram1032** » Wed Sep 26, 2007 8:12 am

very strange....
_____________
I rendered the scene myself now (with water, instead of your material) and it looks just fine...
but my test can't really be counted, as I used far too high values for some of the settings...
which caused (and still causes) a glass, that has a shadow, as if it was solid.
So, you actually can't see the bug in my image (would need to render it for several hours longer xD)
_____________
Hint: You should start from a circle or cylinder and then do exactly the same, as you did, with the cube, to get a better glass^^ (8 - 16 verts might be fine, already...)

sk2k · Post by **sk2k** » Thu Sep 27, 2007 7:44 am

Ok, i think i give up.

Autosmoothing, edge split, etc. nothing fixed the problem.

MfG
sk2k

Heavily Tessellated · Post by **Heavily Tessellated** » Thu Sep 27, 2007 1:20 pm

I don't know, I opened the scene, you have some geometry errors on the glass lip, duplicated verts and overlapping faces, and MAN the density there is insanely high, but even razoring the top of the glass off and making it only one quad across, it still has the same end result.

If you turn off bidir and lower the glass gain, it will probably look fine, sans those beautiful bidir caustics...

Kram1032 · Post by **Kram1032** » Fri Sep 28, 2007 2:57 am

hum... I didn't notice any of these problems O.o
But I had to change the liquid's material

Artifacts with rendered glass

Artifacts with rendered glass

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