Hi,
i just start with krakatoa in Maya and wonder if there is any tricks to create an amount of particles in krakatoa within the radius of the particle in maya, in order to keep the renders looking the same whether the camera is close from the particle system or far.
thanks
Hi!
The original concept of Krakatoa when it was started was that a particle is a point with no size, and you need millions of these to produce the output image.
This was relatively easy to do in 3ds Max since it can produce large numbers of points without much set up. But I can assure you that from day one, people started asking for variable-sized particles. The trouble is that each possible solution (and we have discussed and even implemented a bunch of them) has its pros and cons.
It seems that most people expect us to draw a camera-oriented disk of particles, similar to how facing particles are drawn using cards/sprites. This would require very few particles to be calculated and a lot of pixels to be drawn at render time, so it would be fast, but it would be incorrect lighting-wise.
The alternative would be to produce spherical particle clouds around the central particle, thus defining a volume the light can pass through and get correctly attenuated. But for this to work, all these new particles would have to be created and processed in memory, so it would be much slower than the above approach. We have done this to some extent in two ways - Krakatoa SR and Krakatoa MY now include the particle multiplication option that produces a blob-mesh-like volume with new particles distributed in the volume. When two particles come very close together, they don’t overlap, they merge without producing double the density in the overlapping region. This could be good in some cases, but bad in others. Another thing we have tried is the so-called PRT Cloner in Krakatoa MX (coming to KMY, too) which lets you replace each particle in one cloud with the particles of one or more other clouds. So making a spherical cloud and replacing each particle of a base system with it while respecting the Scale channel produces a similar result to what you asked for.
Another thing we did recently was allowing the Bilinear Filtering of a single point to be spread over multiple pixels. Obviously this is not a direct solution to the above problem because the Filter Size is not view-dependent. But we got immediately requests from beta-testers to provide a channel to control this. Similarly, the DOF feature can draw a single particle as a diffused disk in screen space. This is view-dependent, but based on focal distance and f-stop. So we got requests to allow this to be controlled by a Radius channel to abuse as particle size 
Finally, in version 1.5 of KMX we added the voxel renderer, and in 2.0 we also added an atmospheric effect that works in 3ds Max’s Scanline renderer as well as VRay, Brazil and finalRender to ensure that flying through a dense cloud will produce dense results instead of dissipating into single dots. Krakatoa MX/SR have the voxel rendering mode, but there is currently no way for a single particle to affect more than a single voxel. So a proposal has been made to support the Radius channel and allow a particle to behave as a Sphere that would distribute its Density to all voxels enclosed in its volume.
We are having a discussion about all the various approaches for Krakatoa v3.0 (which would affect all implementations including MX, MY and SR) and we will see which ones produce the best results.
Thanks for asking! 
thanks for that answer, brilliant software. cheers