View Full Version : Crap Glass....

02 February 2003, 11:32 AM
Ok. Here is a small scene i've been working on. Its really simple, mainly to test rendering techniques and glass textures. First off, the chair is from a tut i found on here, and i made the table my self. And, as you can see, the glass texture on the table is a little funky. Its grainy as hell, and i don't know why. I just used the preset glass texture in LW. I didn't try and make my own or anything. So, my question is, how can i make my glass look more realistic. I have searched around, but couldn't find much. Most was for jars and stuff, which really didn't fit what i'm trying to do, which is just a plain flat piece of glass. The table top is just a plain disc, i didn't do anything fancy, just popped it on the top. Any help would be very much appreciated.

[Side Question]

Those chairs are supposed to be a light blue color, kinda like in the tutorial. But when i use this render technique (the one found here ( I am using the last image in the tut to render) the chairs don't come out with the color. Well, they do, kinda, but to see even a hint of blue i have to take the .jpg and juice up the brightness alot. So, my question is, how can i use that same technique, but get the damned color on my chairs to show up?

[/Side Question]

02 February 2003, 01:04 PM
to get rid of the grain you have to increase the gi sampling rate.

For a more realistic glass, add the fresnel shader or use a gradient based on incident angle in the reflection and transparency slot. Glass (and lots of other materials) changes its reflection and transparancy based on the incident angle.


02 February 2003, 01:31 PM
In addition to the suggestions above - for the glass - make sure you bevel the top and bottom polys - give yourself just a bit of edge area for specular reflections. And check out Coffee - you can find it on Flay. It's a "thickening" plug-in (best description I can think of). It'll add just a hint of color in the thicker areas of glass, while leaving the thinner areas more transparent.

The graininess in the glass could be a couple things. As Limbus said, you can increase the GI sampling rate. Or, you can turn on "Shading Noise Reduction" (Global Illumination panel). Or, check to see if there are any bumps in the glass - you can turn them down just a little. And finally, make sure the glass has something to reflect - be it either actual models or a reflection image, or both.

AS for the chairs - check the diffuse channel. I sometimes get strrangely dark colors when using GI as well - haven't tinkered with the settings enough to know exactly why or how to fix them. Sorry. :shrug:


02 February 2003, 02:19 PM
use more points for the glass top, you can see the poly's

02 February 2003, 02:58 PM
Also, you are using a very simple scene setup. It's doubtful that a room is that empty. The point is, the glass has nothing to reflect which makes it look less like glass.

(Photographers also sometimes has to "fake" those reflections to make glass look more belivable)


02 February 2003, 08:52 PM
Good suggestions there.

There are two other things that cause grain on a transparent object in LW other than plain GI.

Lights. Move any lights if you have any on in the scene and see if the grain changes.

Polygon errors. Double sided polygons do this a lot as do subD's that are merged.

Also I would recommend looking at Savinoff's glass tutorial if you haven't. You can find it at the LW tutorials on the web page.


02 February 2003, 10:31 PM
Originally posted by Arte

Also I would recommend looking at Savinoff's glass tutorial if you haven't. You can find it at the LW tutorials on the web page.

Couldn't find that. You have a link?

And thanks for the suggestions all. At the moment i'm trying out all posibilities and techniques. Thanks...

02 February 2003, 07:51 AM
here's the link to Savinoff's tutorial:
tutorial (


Mike RB
02 February 2003, 07:57 AM
give your table somthing to reflect, put in some large white polygons out of the camera frame with 100% luminosity, they will reflect like windows.


02 February 2003, 11:15 AM
Ok, thanks for all the help guys. And as far as my chairs rendering all dark, all i had to do was flip my polys. Here is my best guess as to what happened. When the polys are flipped, you are in reality rendering the backside first. And the backside is in shadow, hence the unison dark colour. :cool: Thanks alot for the help guys. :airguitar

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