View Full Version : Krakatoa.... again...

05 May 2011, 05:37 PM
Hey guys and girls,

I rendered my PFlow with Krakatoa, very simple setup, the only problem is I can my rendered particles, but there is obviously no alpha - this results in the fact that I can view the rendered file with my windows image preview (black background, colored particles in front) but when I import this file into After Effects, it only shows a black image... and when I check the Alpha button in Krakatoa, it has no alpha at all....

Have I forgotten something important or what? Any ideas? I am using 3ds Max 2010 and Krakatoa 1.6

05 May 2011, 06:49 PM
Have I forgotten something important or what? Any ideas? I am using 3ds Max 2010 and Krakatoa 1.6

Yep, the search function :D

It could be one of or some of many things.

The first and most obvious is the Force Additive mode, you will not get an alpha with this enabled.

Less obvious are certain combinations of KCM's and the emission/absorbtion channels, Bobo would have to give you the lowdown on that as I still haven't gotten my head wrapped around that yet. You are somehow creating an additive setup and invalidating your alpha.

Image format, most support alphas yet some don't, if you are rendering in standard jpeg, for instance, you will not get an alpha.

The hack around if you are using force additive mode is just rerender your particles with Force Additive off an steal that alpha in post. It won't be a perfect match but you will have an alpha to work with.

Other than that you are going to have to supply more specifics about you scene setup.

05 May 2011, 06:59 PM
OK well yeah, the long known search bar... :P

other than that, thank you for the advice on the additive mode.... will try that later and post if this was the problem... for the format: I used to save as TGA since I thought it would be one of the formats supportig alpha and transparency...

well yeah - pretty new to all of this, but seems interesting and will sure keep me busy for quite a while :)

05 May 2011, 08:15 PM
We had a long set of posts in the main Krakatoa thread related to how After Effects expects the input to have NON-PREMULTIPLIED ALPHA. Max by default saves Pre-Multiplied Alpha. In Max 2011 and higher, the ONLY way to save non-premultiplied is the TGA format. In Max 2010 and earlier, the OpenEXR also supported that option.

See this post and the messages before it to get an idea of the possible pitfalls. Since we (Krakatoa developers) have never used After Effects in production (Frantic Films used to be a Fusion house, Prime Focus now uses mainly Nuke), these issues are not really well documented yet.

05 May 2011, 09:15 PM
LOL, that totally didn't register that we just had the exact same discussion last week.

05 May 2011, 08:14 PM
Thanks guys, one step further towards wisdom due to your help =)

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