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bfe
09-19-2004, 09:02 AM
Hi,

How do you set up a light in XSI which has a constant circular cross-section (i.e. not focussing or defocussing), and travels a set distance, then stops? I've looked everywhere in the XSI docs for this sort of light and nothing seems to work. Spotlights can't be set without expanding. Infinite can't be set for a fixed distance, and light box, neon and point don't seem to be much use either. All I want is a cylinder of light. There must be something really obvious that I'm missing. That's where you come in...

Thanks in advance,

Ben E

Atyss
09-19-2004, 04:07 PM
Hi,

How do you set up a light in XSI which has a constant circular cross-section (i.e. not focussing or defocussing), and travels a set distance, then stops? I've looked everywhere in the XSI docs for this sort of light and nothing seems to work. Spotlights can't be set without expanding. Infinite can't be set for a fixed distance, and light box, neon and point don't seem to be much use either. All I want is a cylinder of light. There must be something really obvious that I'm missing. That's where you come in...

Thanks in advance,

Ben E
Coming from 3ds max, heh? You can't do that, period.


Cheers
Bernard

bfe
09-20-2004, 02:01 PM
Okay Atyss, good guess.....

In that case, how the heck would you model a laser in XSI? (I mean a constant beam of light travelling between two points, not a star wars-type pulsed effect). Don't tell me that of all the people using this software, there isn't a single one of them who has wanted/needed this sort of capability. Ideally, I'd like to use the raytracing capability of the renderer to set up basic optical systems (e.g. laser source, hits mirror, bounces, passes through lens, focusses, etc), though the impression I get is that to do that sort of thing I would have to write my own software/plugin.

Any help that you can provide would be useful,

Ben E

erebos
09-20-2004, 02:10 PM
why not just use a cylinder with a transparent material with a static blur node and some well tweaked glow settings? then use self-illumination properties to make it give off some light.


That's how i'd do it anyway.


Cheers,
Erebo

Atyss
09-20-2004, 04:18 PM
bfe, if you are into XSI for physics simulations, you are in for a cold shower. Bouncing light on mirror surface is possible only with caustics, same goes for focusing light with lenses. Then you will see that render time can go quite high for anything of that sort that requires precision.

As far as laser beam goes, if you are looking for laser through smoke, you could also create a cylinder and fill it with a volume_effects.


Cheers
Bernard

bfe
09-20-2004, 05:49 PM
Erebos: thanks, I hadn't thought of that particular method. I've been using cylinders with semi-transparent materials applied, but I'll have a go at yours later.

Atyss: Yeah, I know that physics sims are going to be troublesome, but I (personally at home) want to do more general 3d stuff as well and XSI has a good feature set and an outstandingly good student licensing system! Now if only they'd like to deliver the software sometime this year...
I haven't played with the caustics yet, but I know from reading tutorials that the render times are pretty high. The good news is that we're getting a seriously fast dual-opteron computer at uni to run this on, and if I need more power than that, I can connect to a 36CPU cluster that we use for big physics problems.
However, there may be a simpler solution. There's a program called ZEMAX which we use for optical design, which basically does snazzy ray-tracing, and a few other more complex techniques. It has been suggested by my phD supervisor that I try and interface ZEMAX with XSI. (Could be interesting!)
The thing is that we want to be able to do reasonably accurate optics sims (which XSI doesn't like, and can be done in other programs very well), but we want to be able to combine them with decent animation (which XSI is great for, and other programs can't handle).
For example, the first thing I did with XSI (after the tutorials) was to model an optical disc player, starting from the outside, pulling apart the casing and electronics and zooming in to the optical system, then showing the optical stuff. The only problem is the optical stuff.

If you, or anyone else, has any good ideas on alternative techniques, programs, etc, then I would love to hear them...

Thanks in advance,

Ben E

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