Multicolour Point render

[Lummers]

Hey,

I have a smoke trail, using the cigarette preset, coming off a sphere.
How can i change the colour of the trail/particles.
At the moment i can change all the particles to one colour but i want to have a multi coloured trail. Like the emition is red and over time by the end of the trail as the die they go green lets say??
Any pointers on how to do this?
Cheers

[Svetlin.Nikolov]

Hey,

In the Particle Shader, by default, you shade all particles using the same color.

In Phoenix 3.10 we added a Texture map slot you can use to color the particle differently, but it can to so much as a texture allows it to. E.g. a checker won't be too much of a interesting shading, and furthermore, it won't change with time, and even if you animate it, it still won't be able to do much.

So in 3.11 we extended the Phoenix Particle texture. Before, the Particle Tex took the particle positions and created white areas around each particle in 3D space on a black background. Since 3.11, the Particle Tex can color the areas around each particle using a color from a particle channel - e.g. the Age, Position, Speed, or even just the particle RGB. This way you can plug the Particle Texture into the Particle Shader's Color map slot and shade the particles that way.

In your case you would need to use the particle Age and enable the color remap on the Particle Texture, setting the colors near zero (in seconds) to red, and the time corresponding to the particle death (e.g. 1-2 seconds) to the right to green.

One thing you should note is that currently only the Liquid simulator's Liquid, Foam, Splash and Mist particles can have their RGB channel simulated, but the Fire/Smoke Simulator's Drag particles which are used in the Cigarette smoke preset, still don't have RGB channel They do have Age though - you can enable it from the Source.

Another important thing to note is that the Particle Shader still cannot have varying alphas for the particles - this is in the TODO list though.

Cheers!

[Lummers]

Hey,

Thanks for this!

Im having one issue, in the colour from particle channel, when i go to the ... to load up a channel, im getting the error saying 'no particle channel available'?

In the Output of the Sim settings, i have the the age,velocity, RGB, Id all checked on!

How do i get the channels to work to be able to colour the particles??

Cheers

[georgi.zhekov]

Hey,

After you have checked the channels that you need in the Output rollout. You will need to simulate after that so that they will be present in the cache files and to be read by the particle texture.

[Lummers]

Ok, thanks for this. I realised that i hadn't put the particle outputs into the Particle Tex set, so it wasn't able to read!

[Lummers]

Now i have one more issue, when changing the colour in the Particle Tex, as standard it is blue to red, one it doesn't render the new colours, and if i click out of the particle tex and go back into it, the new colours iv put in have disappeared and the blur to red is back??

[georgi.zhekov]

What build of Phoenix are you using and which Maya version? It's best to get a latest nightly build. Here is how to get one - https://forums.chaosgroup.com/forum/...nightly-builds

When remapping the colors - the axis and the range are important. So be sure that you are using correct values.

[Lummers]

Im using Phoenix 3.11 and maya 2017.

Mapping the colour range etc isnt the issue these seem to work, its just actually changing the colours in the colour bar, they just default back to blue and red

When i try to change the colour in the colour bar, i get this error report:

// Error: line 1: setAttr: No object matches name: .partcolor[0].partcolor_p //
// Error: status: (kFailure): Unexpected Internal Failure //
// Error: line 1: setAttr: No object matches name: .partcolor[0].partcolor_p //
// Error: status: (kFailure): Unexpected Internal Failure //

[Svetlin.Nikolov]

Yup, try a latest nightly as Georgi said

[Lummers]

Ok will do!

[Lummers]

Hey,

Ok so this worked which is great thanks.

I have one more question now it works, is it right that when i render the particles with just a flat clour it renders fast, as expected but when i plug in the particle texture the render takes a hell of long time.

I know its working out the colour blend through the particles but i would expect it to render quickly still.

Is there a way to make it render quicker??

Cheers

[Svetlin.Nikolov]

Hey,

How much slower is it? Like 2 times, 10 times, etc? Also, how many particles do you have?

Cheers!

[Lummers]

Hey,

I would say 10 times slower, when rendering a frame in the buffer.
I have about a million and half particles

[Svetlin.Nikolov]

Would it be possible to send a scene and a cache over so we can profile it?

Thank you!

[Lummers]

Wheres best to send to you?