View Full Version : Ray Traced Transparency destroys stars?

02-26-2004, 07:33 PM
OK, I'm having a serious render problem that smacks of bug. I wonder if anyone else has run into this (using 7.5c).

Open up a starfield of single-point polys. Place an object in front of it with any of the following properties (individually or in combination):

-dissolve above 0% but below 100%
-surface with any transparency above 0
-surface with additive transparency above 0

Render the scene with render options set to NOT ray-trace transparency. The stars show through as expected.

Now set it to ray trace transparency. The stars behind the object disappear.

I've tried tweaking anything I could think of (ignored by rays, resetting the alpha channel in both surface and object properties, etc.) and the stars are zapped every time.

I'm wondering if it might be related to another thread from the fall. (http://vbulletin.newtek.com/showthread.php?s=&threadid=8390&highlight=ray+trace+transparency)

Any insights welcome!

02-26-2004, 09:02 PM
Are you sure it's not something really simple, like turning off the "Receive Shadow" option on the starfield object? Just curious...

02-26-2004, 10:37 PM
Raytrace transparency or refraction makes the alpha channel solid, it's a bug that was introduced I think with 7.5.

You could render a separate pass without raytracing and use it's alpha channel -

02-26-2004, 11:44 PM
Thanks for the confirmation, Toby. I suspected it was a known bug, but it's nice to know. I'd kind of figured I'd have to composite a double-render, but it's unfortunate since it involves volumetric hypervoxels <sigh>.

02-27-2004, 12:17 AM
There is easy way to 'fix'

Download demo of G2

Add it to the object
click on it in dropdown
read the wording, click ok (don't try to put numbers or you will be trying to crack it and that's not good). You'll get an error that says number is wrong (cuz you didn't put one there) but that's ok cuz your NOT trying to crack it, now click cancel, cuz you don't need to run it (there will be no interface to run anyways) but it has to be loaded on the line.
Somehow just having it in there fixes the transparency thingy, dunna know why but it does.


Found this by accident when G2 first came out.

Did wine glass tut here;realistic soft drink sweat
to get HVs to render thru wine and a glass.

02-27-2004, 02:42 AM
single point polygons (and two point polygons for that matter), could _never_ be raytraced in LW. After all, the have no real size, so a ray will never be able to hit them.

Try small sprite HVs as a workaround.