Help Mixing Fluids

[josemendez]

I got to ask, why isn't there a proper fluid mixing scene which is 3D?

Because in 3D color mixing is much harder to appreciate. As light travels trough fluids, it gets absorbed by them which means you won't be able to see much going on inside of a thick fluid volume. This being said, 2D can be switched to 3D by simply changing the solver's 2D/3D mode.

Also, because each sample scene tries to showcase one specific use case in the purest/clearest way. There’s no scenes that feature adhesion & rolling contacts, or advection & color mixing, or viscosity in 2D either. If I had to create one sample scene for each possible combination of features there would be thousands!

I appreciate your answers, however using the options that you've listed, it seems that my yellow liquid turned  dark blue and my red liquid has turned turquoise kind of color.   I am using the values from your Diffusion manual, yet for some reason I cannot get the same result. 

That's really strange. Blue (0,0,1) is the exact inverse of bright yellow (1,1,0), and red (1,0,0) is the exact inverse of turquoise (0,1,1). This cannot be a coincidence:
there must be something in your setup inverting the colors, my guess would be either incorrect blending modes or incorrect passing of diffusion data to particle colors.

How are you writing the diffusion user data back into the particle's color channels? I used the sample code in the manual:

Code:

void LateUpdate()
    {
        for (int i = 0; i < solver.userData.count; ++i)
            solver.colors[i] = solver.userData[i];
    }

These are the results I get (red+yellow = orange):

 I really wish there was more documentation for this.

What exactly are you missing or wish to see explained more in-depth? Documentation regarding rendering and diffusion is very detailed imho, each parameter is explained and there's usually screenshot comparisons of different values. It also includes code samples for typical use cases.