# Is there a way to stop Cycles Computing Transparency?

I'm trying out a method of rendering smoke in Blender Cycles through the use of Image Planes and Smoke Textures as Johnathon Lampel shows in his recent tutorial: http://www.blendernation.com/2015/07/04/faking-smoke-with-particles-in-cycles/

This is my current result:

And this is my node set-up:

As you can see, in order to prevent cycles from rendering transparent planes at the back of the particle system as black I've had to bump my Transparency Light Path Bounces up to a Max: value of 56, which in turn takes a while to render (1min 56secs on half-res 10 samples).

I feel that it should be possible for Cycles to simply disregard Transparency, so instead of computing it as a bounce, it just treats it as though it's not there, rendering the smoke image but not the alpha surrounding it. As a result this would drastically save on render times.

Does anyone know if this is possible? :)

Thanks!

• That's.. exactly what it does. It still has to perform the intersection check on the ray in order to know if the ray hits anything, which (AFAIK) is the slow part. – gandalf3 Jul 7 '15 at 0:21
• Thanks @gandalf3 I understand that, but I'm wondering if there's a way to stop it treating something as 'transparent', and instead just treating it as though it isn't there. It's hard to describe exactly what I'm getting at. Basically, how disabling the Camera ray visibilty essentially stops an object being seen and rendered through the camera, is there something similar that prevents transparency from being rendered by the camera? If that makes any more sense? :/ – Hexbob6 Jul 7 '15 at 0:29

• Ah well, thanks for the reply PGmath. I guess it was wishful thinking on my part, but I was wondering if there isn't a setting directly in cycles, whether it could be achieved through some fakery with the Light Path input node, or something along those lines? – Hexbob6 Jul 7 '15 at 12:37