Alpha with X-Particles

[anon54601079]

Hello

I’m new to Krakatoa so forgive me if this seems obvious.

I’m generating particles using X-Particles. I have an image sequence which I’m using as a plate to emit from. In my emitter I have the ‘Emit Channel’ set to Alpha, so particles are only emitted from the white of the Alpha Channel and in my ‘Colour Channel’ I have the RGB of the plate.

Using the Krakatoa X-Particle Source I get what I expect, particles with the correct colours and emission only from the white areas of the plates alpha.

However once I partition out a sequence and load it back in with the Krakatoa PRT Loader, particles are emitted from the black areas of the plate, which is wrong. So the whole frame emits particles, these particles appear grey in colour.

In my X-Particles source I have:

Velocity/Age/Colour/ID/ Age/ Normal/ Transparency/ Birth Position

In my ‘Save Particles’ dialog in the render settings I have:

Position/Velocity/Colour/Density/ID/Normal/Emission/Age/TextureCoord/Birth Position

---- I just did another test and only selected Position/Velocity/Colour Float and I get the same results—

I have to admit I’ve enabled some channels I probably don’t need to try and figure out what is going on.

In my partitioning I have save multiple partitions selected- Total Partitions 10, sub range 1 to 2. Increment Emission Random seeds is checked.

I have a Channel Set tag on my PRT loader with a float value of 1 for the density, as I wasn’t getting any density information before this.

I’d be very grateful for any help with this.

Thanks
Stephen

[Bobo]

Hi!

This is very strange, it sounds like the X-Particles starts ignoring the Alpha as soon as the scene is saved for Partitioning.
Normally, Krakatoa should be saving exactly what it is rendering (in other words, saving particles is a form of “rendering to disk”).
Btw, are you using the Render Queue or Deadline for Partitioning?

Can you please try using the Save Particles To File Sequence option of the renderer to produce ONE sequence without Partitioning?
Just switch to Save mode and hit the render button to produce a PRT sequence.
Then load with a PRT Loader and compare to what you are getting when rendering directly, and to the PRT sequences from Partitioning.

If the sequence is ok, then we will have to figure out whether the temp files saved for partitioning have changed somehow - you could load the scene files we send to the queue and see how they would render in interactive mode.
If the sequence is also wrong, we will have to figure out why the renderer would get different particle distribution when saving vs. when rendering directly.

Thanks for your feedback and sorry for the inconveniences!

[anon54601079]

Thanks for the very very quick reply, Bobo.

I think I might have solved it. In the X-Particles emitter is a contrast slider, I upped it a little and it looks like it’s solved the problem. It is strange though since I checked the RGB values in after effects and they were definitely black. Could it be a gamma thing?

Will post anything else I find here!

Cheers

Stephen