hey
im trying to create a galaxy with krakatoa and heres how its looking, just got the dust pass atm not sure how to create the stars, got any suggestions
no one able to help? any one know how to set up the kcm to use color by density ( orange/ red for denser areas blue for less dense) and random opacity?
This tutorial about using Krakatoa to generate Color based on a particle’s Age is similar in spirit to what you are asking. http://www.thinkboxsoftware.com/krak-magmaflow-fading-by-age/
How are your particles created? Krakatoa uses a per-particle channel called “Density” that is essentially a weight for the particle. You can use that value in a KCM to do pretty much any sort of shading you’d like.
If I understand correctly you are looking to work with a slightly different quantity that I typically call spatial density. This is based on the number of particles per unit volume (ie. the classic meaning of the word density). In areas with lots of nearby particles this is higher than areas with few scattered particles. Unfortunately Krakatoa does not have any tools for working with spatial density. If you can find tools that allow you to compute spatial density (Particle Flow Box #3 comes to mind), you can save that channel and have Krakatoa use it in shading calculations.
This is also a pretty good tutorial for using Krakatoa Channel Modifiers to shade particles with various inputs: http://www.thinkboxsoftware.com/krak-magmaflow-gijoe/
thx for reply,
all my particles are spawned at the same time in a circle emiter so age isnt gona work,
are those tuts the effect they used in gi joe
No, just some effects we demonstrated at Siggraph to show how KCMs work. Basic stuff, really.
The setup for G.I.Joe was significantly more complex 
When you spawn all your particles, how do you decide where they will be placed? If you have some method of determining some sort of weighted random position for where the particle, that weight data can be passed to a Krakatoa Channel Modifier to be used to control particle color or opacity. You could write it to a map channel if you are using Particle Flow, and have the KCM read the values back for processing.
In Krakatoa opacity is related to a per-particle “Density” channel, and color is determined from a per-particle “Color” value.
i use 2 vortexs as a force, they have differnt settings to simulate the gavitational falloff thus making arms
and i simulated it to frame 92 i thnk then saved all the particles with 10 partitions and am using the prt loaded
heres a star pass wip, frankly it sucks lol
I think you need to decrease the integration step in particleflow. It will help with the lines of bunched up particles where the linear integrator doesn’t approximate the circular motion well.
integration step?
PF_Source > System Management rollout > Integration Step group of controls > Render > “1/8 frame” or shorter. Default is 1/2 frame, which means PFlow updates the particle position by adding a fraction the velocity to it 2 times per frame (and of course updates the velocity according to the forces etc.). The shorter the period, the smoother the results at cost of performance.
ah ok thx
mrh vortexs arnt working that great, any one know any alternitives, im trying sperical gravity with a vortex but is their some other way of creating rotation
if its going to be a still and not animation, you can always cheat and use textures to darken / lighten certain parts. I think its easy to get caught up trying to make things as accurate as possible and forget when forging with the computer, you are in control – and thats one of krakatoas strengths is taking ALL of the values you throw at it and give you full control. i say you need to save out your last frame (92) with all of the channels. the more channels the more to play with!