Special Glass rendering

[Bertell Teores]

Hi!

I would like to ask for some help with a project. I am trying out Rhino and v-ray. I have a special artistic glass that I would need to integrate in to a scene, however I met some difficulties. I am already familiar with special glass surfaces, frosted, bumped etc. I tried to make photos of the surface to make the proper bump maps with no avail. This glass material in reality has small bubbles in it, and soft lines on the surface. Do you guys have any Ideas how to recreate it?

Any help appreciated!

[Tom Bussey]

I'm coming from a 3DSMax background here, so I might not be the best to comment, but I love a challenge
There's a few things going on with that material that might require different techniques but I can try and give you some pointers of what to play with:

The bubbles are the main issue, unless I'm mistaken, without a volumetric material this cannot be calculated, and you don't want to do that anyway as it'll be very heavy computation wise. Since it's a product of differences in refraction I'm going to guess something similar could be produces with a map in the Refrection IOR slot. IOR works kind of strangely, and small differences in value will make a big difference in effect, but essential set at 1, light will go straight through without changing path. normal glass is 1.6 which mean it deflects slightly, but not massively noticeable. below is the version I managed using 3DSMax's inbuilt noise map, you might have to experiment with creating maps in photoshop though. Just be aware that small differences in tone will have a big impact in effect. For some reason I think Vray make IOR 1 an RGB value of 255 and IOR 100 a value of RGB=0 so I gues 1.6 would be , but even if you try and be exact you'll have to take account of any gamma correction on the bitmap.

The other method would be to boolean out the holes with a particle system, but I don't think that's possible in Rhino.

Fog colour - for the colouring. Be aware that the opacity of the material will be dependent on thickness, so make sure your mesh is a closed one with a sensible vale to the thickness (whack a shell modifier on it for the easy way)

Refraction glossiness - you can see how the light is more dispersed than the light coming through the clear glass behind it, that's your reflection glossiness, I'd start at a value of about 0.8 to 0.9 at a guess.

There are some straight lines going diagonally across the face of the glass, I can't work out whether that's a surface texture or some kind of crystalisation effect within the glass. Either way you'll need a texture of some kind, either a bitmap/jpeg/tif,. I've used a 3DSmax inbuilt map again.


Basically, it's possible in max to bodge it, but I'm not sure if it really is in Rhino, because of the (possible) lack of inbuilt procedural maps and OSL maps.

temp.tif

[Bertell Teores]

Hi Tom!

I am so grateful for your comment on this. I will continue with experiments based on your suggestions. I think volumetric material could be a perfect solution, however I think it is not available on V-ray for Rhino.

The effect you were referring is caused by tiny embossed hairlines on the glass surface, on one side only. I found an image where I am cutting it. The lines can be seen on top.  I am attaching a closer image of the glass piece as well, since uploading it degrades the quality of the photo. I have also tried to make a "map" by lighting the glass from top and take photo of the shadows. I could not really use that with a result.

Thanks.

 

[Tom Bussey]

Actually one thought just occurred: you could try taking your shadow map there, make it monotone and normalise it to black and white, then plug it in to a bump map. That'll affect your reflections too, so maybe try that on a 2 sided mesh with a smooth glass on the side facing the camera, or on a one sided mesh with a 2-sided material. It'll take some experimenting for sure, but could be fun finding out.

Good luck!