My current situation with Cycles nodes:
I'm trying to make particles turn from dark to bright in time. So the Particle Info node has output "Age". But Sticking that value into Mix node produces no or complete change in the mix. So I start trying to math-fix it. I found out I can divide the value and that makes it work, but the particles turn from one to the other too fast, I can only control how far off they suddenly change.

How am I supposed to understand the values? Is trial and error the only way?

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    $\begingroup$ possible duplicate of "Map Range" node equivalent for Material nodes? $\endgroup$ – zeffii Sep 13 '13 at 18:37
  • $\begingroup$ I realize the wording you use is different, but the answer I gave to this question answers this question directly. (ie, How to make particles turn from dark to bright in time.) $\endgroup$ – zeffii Sep 13 '13 at 18:38
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    $\begingroup$ @zeffii, yes your answer does the trick, but I think he asked more about how to "visualize" the values of a node's output (and understand it). I can't figure out how to, though... $\endgroup$ – Polosson Sep 14 '13 at 22:33
  • $\begingroup$ could you visualize it with a combiner node to produce a color? $\endgroup$ – 3pointedit Sep 15 '13 at 6:54
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    $\begingroup$ Just connect it to an emission shader. This acts as a sort of viewer node - it has no shading on it and is quick to render. Possible duplicate of blender.stackexchange.com/questions/1691/… $\endgroup$ – Greg Zaal Sep 16 '13 at 9:20

The Age output of the Particle Info node is measured in frames (like the particle setting itself). So the simplest way of normalizing the value (get it into 0..1 range) is to divide by the Life setting of the particle system: enter image description here

You can also divide by the Lifetime output of Particle Info, giving the relative age for each particle: enter image description here

Note however that the Lifetime value can vary for each particle depending on the Random factor in particle settings:

Divide by constant:

enter image description here

Divide by Lifetime (with Random = 0.75)

enter image description here

  • $\begingroup$ Ok, but in general, how do we know the output range of a node? $\endgroup$ – endolith May 11 at 11:13

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