Rendering models (or part of) as glass

CD Xbow | 2012-02-12 22:48

Somewhere I have seen a discussion in one of the cube related forums about trying to use the glass material in a curved fashion; it seems you can't. It is the Cube engine after all.

My interest is mainly to do with recreating those round glass transport tubes you see often in scifi imagery of the surface of Mars. Using RE I used the translucent entity property applied to a hollow model , didn't look right, then I thought maybe I could use a custom shader on the model. I looked to see if someone had done a glass model shader but could find none. I experimented for a long time (had a lot of fun) but didn't get anything to look how I wanted. So my questions are:
1. is it possible?
2. has anyone done it? (and know a link)
3. if it can be done, but hasn't, can anyone point me in the right direction.

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Suicizer | 2012-02-12 23:14

Perhaps here is some useful information about it...

Generally, the envmap shader is used to reflect the outside, just like glass does often. The transparency can be caused by using a skin which is in a .png-format, while using the alpha-channel.

There once were some models which were appearing to be glass. It's just right over here.

typhoon | 2012-02-12 23:25

The alpha material should do the job. Otherwise, what Suicizer said.

CD Xbow | 2012-02-12 23:39

Thanks a lot. I've loaded them up and they look pretty close. I will try them on a tube later and see how they look. Certainly a lot easier than a custom shader.

Suicizer | 2012-02-13 17:45

Well, the benefit of a custom shader would be that it could be used for anything. Like if you would be able to let the reflectivity shader of water also work on textures, then your problem is finished (as it's reflecting it's environment "real-time").

CD Xbow | 2012-02-20 05:10

The effect looks more like a force field rather than glass, useful still. In a cylinder, the strobey effect was prominent. I rendered the horned dude from saeur(?baull), it gave a nice, ghosty effect, bit like cortana from Halo. I think using a shader may be required to get a more convincing effect.

Suicizer | 2012-02-20 17:21

Keep in mind when using a custom shader and releasing it officially (like for a a release of Sauerbraten), it should also be compatible with glsl-rendering. So people won't get nasty looks when checking out the geometry which the shader is assigned to.
For anything else like that, it's irrelevant...

restcoser | 2012-02-20 21:36

I tried a cuved glass effect, it actually works, but requires much tweaking.

Please notice I did this in Cube 2, not RE, but I don't think that's much of a difference.

1. I took a texture with shader bumpenv*, for testing the texture trak5/glass.jpg worked fine, but you might want to create your own, preferably a plain white texture

2. I used /vscale 30 to make the glass appear uniform.

3. I set /vshaderparam envscale 1 1 1 for a good reflection effect

4. I used alpha-material for the geometry

5. I added lights and an envmap

6. I tweaked /valpha. Everything between 0.4 to 0.7 looked acceptable.

7. /remip;calclight;recalc

Suicizer | 2012-02-20 22:10

This technique already has been used in some maps, like Fatal Instinct. Thanks anyway for notifying the rest of the community.
The only difference is the alpha material though...

RaZgRiZ | 2012-02-20 23:32

Actually the scale can only go up to x10, so a value of x30 doesn't actually exist :P

restcoser | 2012-02-22 12:04

good to know :)
so it resets to 10 then?

RaZgRiZ | 2012-02-22 12:32

10 is just the max, even if you use 10000, it will be clamped to 10 :P

Suicizer | 2012-02-22 18:41

No, as it's capped till 10. Any higher values will just have the same result.
An example on that is like "/fullbrightlevel 28354169". It will just be executed with it's maximum value of 255, but the only difference is that it will turn up an echo which says "valid range for fullbrightlevel is 0..255". This isn't happening on vcommands (yet?).

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