View Full Version : Diffuse + Transparency: Something EVERYONE needs to know!

01-19-2009, 08:57 AM
Despite using LightWave for years now, I never knew about this!

Essentially, if you're using transparency AND diffuse (for say glass) you will incur a massive render hit. This is probably more noticeable for scenes with Global Illumination, I've not tried it with non-GI yet.

But it's such a slow down that you NEED to be aware of it!

I'm told it's something that is NOT unique to LightWave either.

I'm sure many might have known about this (if so, why didn't you tell the rest of us!) :D But many may not be aware, I know I wasn't!

Anyway, watch the video to see the issue.

Quicktime H.264 (6mins, 6MB RAR Archive)
Video Tutorial: Diffuse Transparency Slowdown (www.creactive-design.co.uk/lightwave/tutorials/Diffuse_Transparency_Slowdown.rar)


01-19-2009, 09:01 AM
Just want to point out, the slowdown may not be as pronounced on some scenes, just so happens with the Preset Standard Scene it was very obvious!

01-19-2009, 09:35 AM
It makes sense when you think about it. It's more difficult to calculate both light reflecting and penetrating the surface.

However, I haven't experienced any major issues with using both. It's slower but, hey, that's why we are buying hardware :)

Thanks anyway!

01-19-2009, 12:23 PM
Hmmm...haven't noticed this problem,yet. Thanks for the heads up!

01-19-2009, 12:38 PM
Not a problem if you aren't using GI, but as soon as you use it, boom.
It accounted for why one of my scenes seems to go glacial for no obvious reason.
I dropped the diffuse off it before and the speed up was very noticeable.