Glass Help

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Glass Help

Post by Post » Wed Jun 25, 2008 2:29 am

I have received a sample of glass for a project I'm working on. I have been having trouble trying to match it close enouh in skindigo. I hoping that some of you met give me some suggestions on which materials to use to give me a better quality result. The first 3 images have figure prints (oily marks) which will not be on the final product. All the photos were shot at the same time.

I have tryed the preset - frosted glass for the sand blasted area and the a transparent glass with a colour blue but the transparent rendered clear and the frosted glass was grey/black on all angles.

I look forward to you comments and thanks for any suggestions that you can offer.
Attachments
1.jpg
Real photo
1.jpg (233.87 KiB) Viewed 3773 times
2.jpg
Real photo
2.jpg (249.27 KiB) Viewed 3773 times
4.jpg
Real photo
4.jpg (161.56 KiB) Viewed 3773 times
3.jpg
Real photo
3.jpg (157.08 KiB) Viewed 3775 times
im1214314248.jpg
rendered image
im1214314248.jpg (104.46 KiB) Viewed 3776 times

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zsouthboy
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Post by zsouthboy » Wed Jun 25, 2008 2:51 am

Create only one material, and make a high-frequency bump map to "frost" the areas you want frosted.

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Post by Post » Wed Jun 25, 2008 3:25 am

I have not played around with bump maps yet. Still learning what materials do what.

One material for the whole piece? Should the "image" (clear glass area) be rendered with this material too? Or should I have to materials, one with the bumpmap and the other without?

Thanks for your help.

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zsouthboy
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Post by zsouthboy » Wed Jun 25, 2008 3:37 am

I'm not a Sketchup user, so I can't give you specific instructions on how to do this (I hear UV mapping is limited in Skp :(), but yes: create one material for the glass.

The "clear area" should be bump mapped with a non bumpped area of the map (so light is unperturbed), the rest of the front of the glass should be mapped to the high frequency bump of your texture.

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zsouthboy
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Post by zsouthboy » Wed Jun 25, 2008 3:51 am

Here's an example I threw together. The plane has thickness, and I've applied the bump map to the front of the plane (so that the other side is not blurred when viewed through)

Suzanne in shiny red is behind the glass.
Attachments
frosttest.png
The bumpmap i used
frosttest.png (957.09 KiB) Viewed 3726 times
im1214321901.png
2 minute render.
im1214321901.png (282.77 KiB) Viewed 3726 times

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OnoSendai
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Post by OnoSendai » Wed Jun 25, 2008 8:24 am

The other way to do it would be to use a glossy transmitter, and use an exponent map. zsouthboy's way might be easier tho.

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zsouthboy
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Post by zsouthboy » Wed Jun 25, 2008 8:30 am

hmm. I'll try that too. I've been mulling the idea over a bit to see how I would most closely get to the reference photos (It's tough to make the "frosted" part appear to absorb enough light to be convincing. Might end up modelling the damn thing.)

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OnoSendai
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Post by OnoSendai » Wed Jun 25, 2008 8:35 am

Actually, having said that, I never got round to enabling exponent maps on the glossy transparent object. So forget that :)

Although another way would be two blend two glossy transparents of differing exponent together, which would actually probably be easier.

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cpfresh
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Post by cpfresh » Wed Jun 25, 2008 9:01 am

... i tried the modelling method, it looks ok.
Attachments
im1214338941.png
im1214338941.png (480.23 KiB) Viewed 3637 times

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Post by Post » Wed Jun 25, 2008 9:31 am

Thanks for all the tips... Tomorrow morning I'm going to try and figure out how to do the suggestions. I wish I had more experience on skindigo … I guess that comes with time…This is my first major project and there is never enough time to fully learn the program that make outputs look the best. </Rant>

cpfresh nice render of a clear glass with a light sandblasting. I'm aiming for a blue glass with a more opacity to the sand blasting, similar to the photos at the top of the thread. Did you use zsouthboy’s suggestion for the clear area?

Thanks.
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cpfresh
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Post by cpfresh » Wed Jun 25, 2008 12:03 pm

thanks post. nah i modelled a thin layer of sandblasting and stuck it on top of the normal glass solid ... physically incorrect but it looked close.

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cpfresh
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Post by cpfresh » Thu Jun 26, 2008 4:23 am

ok so i tried blending two glossy transparent textures and this is the result. the difference is barely visible (but it is there if you look close)

my exponent settings were 100 for frosted glass and 1,000,000 for the normal glass.
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im1214354891.png
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zsouthboy
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Post by zsouthboy » Thu Jun 26, 2008 4:39 am

Exponent for the glossy glass should be lower than 100 for a contrasty result - try 1 instead.

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cpfresh
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Post by cpfresh » Thu Jun 26, 2008 5:08 am

trying exponent 0 now ... allowed? dunno. but indigo accepted it. will post render in a few moments. another thing i forgot to mention, the two materials are sharing one internal medium name, which i never thought of looking at until Ono suggested it.

*edit* zsouthboy, show show!!! :P
Attachments
im1214412738.png
im1214412738.png (465.87 KiB) Viewed 3494 times
Last edited by cpfresh on Thu Jun 26, 2008 6:09 am, edited 1 time in total.

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zsouthboy
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Post by zsouthboy » Thu Jun 26, 2008 5:52 am

I got it!

Testing now :D :D

EDIT: Yes! It matches the reference almost exactly. I'll let it clear up a bit then upload and explain.

EDIT2: Okay images are attached.
Here's how to do it:
Glass pane:
Specular, 1.5 IOR, a little absorption of green.

Create a plane (1 sided, normal pointing towards camera) slightly INSIDE (but greater than ray_nudge_distance) the front of the pane of glass.

3 materials needed:
A)Diffuse
B)Blend of (A) and null using imagemap (attached)
C)Blend of (B) and null (I used 0.1 as the blend factor - adjust to taste)

Use (C) as the material for the plane.

Adjust the closeness of the plane to the outside of the pane to taste.
Attachments
frosttest.png
Imagemap
frosttest.png (30.43 KiB) Viewed 3497 times
im1214416127.jpg
Render result
im1214416127.jpg (49.54 KiB) Viewed 3497 times

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