View Full Version : Help with Glass

11-18-2011, 10:13 AM
I'm building a news open which has glass panels as part of the elements. I've attached my PhotoShop Design Comp and a test render.

Refraction and the background:
I'm not clear why the glass is not showing the background image through it and/or refracting it.

I've used Robin Woods tutorial on setting up glass surfaces http://www.robinwood.com/Catalog/Technical/LightwaveTuts/LWTutSet.html which uses fast fresnel as well as flipped duplicate geometry for refracting but I'm getting the black background the scene is built over through the glass and not the background image placed there.

Do i need to map my background on a piece of flat geometry for the glass to react to it? Also what do I need to adjust to make the glass clear like the design. I've tried it wih 0 blurring and there's still this bump effect (bump is off (0) too).

Increased Refraction:
On my PS comp I've designed a serious refraction. Is this achieved by settings or position of the glass further from the model to refract? These are time consuming render tests so I'm hoping to tap into the community for shortcuts rather than extensive render testing.


11-18-2011, 10:30 AM
to be honest it might just be faster if you do the glass refraction effect in AE, im sure theres a way to achieve it in lightwave but it sounds like you dont have that kinda time to trouble shoot it.

Oh try checking off noise reduction and set it to final gather if you havent already. may help, the blurring in your glass looks like its a radiosity issue.

im assuming you want the glass to kinda look like this link here

11-18-2011, 10:40 AM
Use the Dielectric material?

11-18-2011, 11:10 AM
Agree with dielectric material. (Robin Wood tutorial was written before material nodes, I believe.)

Also, your ray recursion limit must be at least 1+the number of transparent polygon layers (double sided Ithink counts as two) for light to travel through them. Otherwise, those polys behind all the layers of transparency will render black, but you probably knew that.. Not sure if that pertains to your scene.

11-18-2011, 11:14 AM
Use the Dielectric material?

dielectirc node : add small roughness select you Ri 1.2 upwards and absorption is done on scale I believe ,be using nodes you will way more control over the materials and render times will be just that little bit faster

11-18-2011, 11:38 AM
I'm at a pretty high proficiency level with After Effects and am seriously considering doing it that way. This is for an internet news program and they want it real short so 3D wouldn't be insane (~5secs.). The thinking is it would get pretty redundant if it was longer and preceded each news brief.

Still building the whole animation in 3D and just rendering the glass planes and their bevel separately would match the moves with the logo which could then be used as mattes in AE to matte in larger versions of the 3D and some highlights. Could be pulled off that way.

I think I'll experiment with some of the suggestions and make the call after I see what I get.

I am by the way using doubled up glass geometry with a copy having normals facing out and the other with normals facing in for the refraction (all covered in Robins tut).

Thanks for the feedback.

11-18-2011, 12:12 PM
I am by the way using doubled up glass geometry with a copy having normals facing out and the other with normals facing in for the refraction (all covered in Robins tut).

That technique is redundant now that we have dielectric. It does all the work for you without the need for double sided polygons and 'air' geometry.

11-18-2011, 01:58 PM
Who new, I'm still figuring LW out. THANKS!


11-18-2011, 02:11 PM
In fact, if Iīm not wrong the doubled polygons and "air" technique is redundant, not because of the dielectric material (which is great, if a tad slow at rendering) but because of the VStack changes which make now LW interpret transparent objects as "filled/solid", unless Double sided is checked (in which case it acts as if it had "paper-thin" thickness)

11-19-2011, 06:16 AM
Hmm, wasn't aware of that, good to know.

11-21-2011, 03:10 PM
here it is again.

1.) why is it that when I use geometry to texture map a background the transparent geometry reacts to it but when I use the background image option my transparent geometry doesn't allow it to be seen through? I've posted images of both render settings.

2. Can any experienced node LW user check my glass node settings and tell me if these look like they could improve my glass any more?

Thanks to all in the community that helped me get this animation this far. I've learned a lot.


11-22-2011, 03:21 AM
1) Iīm afraid you donīt understand properly what the "Background Image" option does. When you put an image there, it is NOT interacting with the 3D scene at all. Objects will not reflect/refract anything you put there, nor radiosity color will be affected by that background.
Itīs meant just for compositing purposes.

2) Well, my first question regarding the node setup you got there is,...do you really need all that? :D I mean, it looks ok, but just a dielectric material, should give you quite a nice refraction effect. I would only tinker with the nodes to imitate glass if I couldnīt use dielectric because of render times or something similar.

11-22-2011, 03:29 AM
What version of LW are you using, DI?

It looks like you're still faking Volume Stacking.
You only need to apply the dielectric material these days. Additional nodes are only required for advanced reflection options etc.
For realistic glass, the material does it all.

11-22-2011, 09:04 AM
Thanks for the response. The version I am on is LW10

I didn't properly understand what the background was for - makes sense and will adjust accordingly.

The nodes setup I'm using is from a tutorial on how to make glass using dielectric. Good to know it isn't that complex - I was thoroughly confused.

What's the best method to texture map text onto a flat rectangular piece of geometry and what file type should my texture map be. I'm using a 32bit TGA file (white text on black in the alpha channel and a white RGB). Not getting the results I'm looking for using either Alpha or PS Screen mode with either planar or flat with automatic sizing.


11-22-2011, 09:41 AM
What's the best method to texture map text onto a flat rectangular piece of geometry and what file type should my texture map be. I'm using a 32bit TGA file (white text on black in the alpha channel and a white RGB). Not getting the results I'm looking for using either Alpha or PS Screen mode with either planar or flat with automatic sizing.

What results are you looking for and why are you disappointed?
A TGA or PNG used as you've described should work fine but without knowing more its difficult to advise.

11-22-2011, 12:33 PM
If you go to my initial post there are two images. The first is my design and you'll see text that says things like investments, annuities etc.

My desire is to texture map this text onto a flat rectangular piece of geometry and have just the text visible. Simple task in other three D programs I've used but haven't figured out the best method for doing it in LW.

Everything that seems to be a logical way to do this from my experience doesn't seem to work. Like I would think mapping flat, edge to edge with auto size to the geometry using a 32 bit image with a white RGB channel and the text white on black in the alpha. Using the alpha mode should work fine. I'll try just white text on black in the RGB channel and use the PS Screen method but I suspect a PNG with no background would result in the geometry still being visible.

Thanks for any help you can offer.

11-22-2011, 02:01 PM
I'm not sure I understand, but I'm the dumb bunny of the group. To do what you describe, I would type my text in PS on a transparent bkgrd...any 32 bit format, I think. Then put it on my poly with the attached setup. Forget screens and channels.

11-22-2011, 03:35 PM
I'll give this a shot. I'm still trying to do everything the old way (before Nodes) because I don't really understand them yet.

Your arrangement looks correct but (and this is a newbie speaking) Why would you even address the alpha if one doesn't exist in a PS document that has no alpha?

A PS doc with text on a blank background requires no alpha because it isn't being keyed. The white of an alpha is the cookie cutter that punches out whatever is in the rgb channel in the same place as the alpha. A PS file (or png) is self keying by the very lack of a background. What you see is what you key to put it simply.

Thanks and I will try your technique. If it works I'll be even more confused because it will further make no sense "to me" (being really well schooled in alphas).


11-22-2011, 03:37 PM
As a slight aside, MGImagesToPlanesMD (http://www.mikegreen.name/Lscripts.html) is one of my favourite Lscripts and will automatically make a plane to the dimensions of your image - MASSIVE time saver!

I've run into fringing problems with Rabbitpenny's solution. There was a post that works a lot better with a simple tweak, I'll try and hunt it down..

Edit: here's the thread, check out post 5, works a treat.

Ps. Sorry, I have just re-read your post and not sure it's what you're after but it's useful to know :)

11-22-2011, 04:11 PM
and Penny, I'll try this.


11-22-2011, 04:17 PM
If I understand, you might be looking for Clip Maps. It works like alpha mapping but masks unwanted geometry more efficiently.

The function is found in the Properties (under the Render tab) of an object.

11-22-2011, 05:03 PM
I forgot to mention, if you have spec, gloss, reflec, etc., applied to your image, you'll have to zero those out using the alpha channel.

Notice, by the way, the image node starts with a backgrd color (default Black). In other words, there's never nothing there. The image's alpha channel is used to remove that background info. At least I think so.

In this circumstance, either the node solution or clip map should work.

11-22-2011, 06:20 PM
This is exactly what I'm trying to do and what is relatively simple in other 3D apps. Remove unwanted geometry with the black portion of either the texture map (as in Screen Mode in After Effects) or with an alpha channel like in PS.

I'm just trying to familiarize myself with the features and terminology that do the same thing in LW.

I'll get it.

11-22-2011, 06:27 PM
Yes Clip Map is what I was looking for, Just did a quick test and got the result I was looking for.

Thanks you Thank you - Moving forward again.

11-25-2011, 12:27 PM
BTW Happy day after Thanksgiving to those who celebrate it.

Is there a way to solo a single piece of geometry so in one click you tell the render to ignore all other geometry in the scene to speed render testing?

If not that would be a great feature. Just turn off the geometry you don't want to render and leave what you're working on. I'm aware of turning off the camera for each piece but it would be easier to just select a piece of your model and say ignore everything else.


11-25-2011, 12:29 PM
Yes, just select that object and press F11.

11-25-2011, 12:53 PM
And yes the liver is naughty for sure. Bad liver! Take That! snort.