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View Full Version : Alpha problem in 8.2



NigelH
04-05-2005, 08:05 AM
I've found that LW 8.2 will render a degree of alpha transparency onto a referactive object when 'raytrace refraction' is turned on - even if it isn't required. I know that's pretty vague, so to illustrate, I have rendered an object in both LW 8.2 and LW 7.5 (below). LightWave 7.5 renders the alpha correctly while 8.2 insists on adding transparency on the three lenses where none is necessary.

In the case below, if 'raytrace refraction' is turned off, the alpha for the lenses returns to normal (i.e. blocked by the alpha for the character's head).

In this case, my solution is simply to render the animation from Lightwave 7.5. In other situations, the solution may not be so simple. Can anyone replicate this, explain why this happens or tell me I'm doing something wrong? Or should I add it to the 8.2 bug list (if it's already there, I must have missed it)?

I'm using LW8.2 on MacOS 10.3.5, by the way.

Celshader
04-05-2005, 08:12 AM
I do not know if this is the best solution for 8.2, but you can mark the refractive surfaces with constant Alpha Channel values of 255. The option to do so is in the Advanced Tab of the Surface Editor. Choose "Constant Value" from the "Alpha Channel" drop-down list, and set it to 255. Then the lenses will always show up as white in the alpha channel.

NigelH
04-05-2005, 08:23 AM
Thanks, I just checked that, and it works. But what happens if you have a transparent, refractive object and an opaque object passes behind it? Happily, that's not the case here, but I certainly hope it's something that's being looked at for the next revision of LightWave.

eblu
04-12-2005, 10:31 AM
i would render a second pass, with the background Object as the only object in the scene, and then composite the whole thing myself.
easy to do actually.

when your ready to render that second pass, change the save to file options (so that you don't overWrite the original render) select the background Object, and then hit the F11 key. it renders only what is selected. if your lucky, you only need to render a few frames.