hi all,

i was watching this tutorial “fire and smoke technical evening” by Mario Marengo. i was wondering and guessing what was the expressions he put on the isooffset node that make the sphere volume goes from 0 to 1, and from 1 to 0?

i saw him put this one on the volumemix2 node:

1-smooth(length($X,$Y,$Z), ch(st … something)

though i notice he has new parameter in the volumemix2 node too.



and for the volumemix1 node:

max (0,$V/0.916852)


i wanna know the expression there, so perhaps if anyone knows it, it would be really helpful.


Thanks in advance for the help!

San

From Mario himself :-

Mario Marengo pyro shader master class question


“Early on in the section about volumes and your base set up. You talk about using a volume mix for the temperature volume , using the function max(0,$V/0.999)”


Answer:-


Hey Rob,

I was just normalizing the range to (though I agree that 0.999 seems awfully close to 1.0 already, so it was probably there mostly to remove negatives more than to fit the top end – are you sure it read 0.999?).

Anyway, what I was trying to show was that, given some generic volume, you can use the volumemin() and volumemax() expression functions to find out the extents of the raw incoming values and then fit them to an exact range (assuming this is desirable). And one way to do this would be to divide the volume values ($V) by the reported MAX value (reported by volumemax(), that is), then discard the negatives, which can be done with that expression “max(0,$V/MAX)”.

Of course, you could always use the fit*() functions if you want more specific control.

That's all I was trying to convey there.


Hope that makes sense.

Cheers!


You might also want to grab yourself my read volume data tool from the exchange !

Rob

Hi Rob,

sorry for the very very late reply…
oh, so that's it for the expression max (0,$V/0.916852) ?
it's kind of make more sense to me now.


but what about the other expression:
1-smooth(length($X,$Y,$Z), ch(st … something)

do you know what is that he is channelling to? regarding I see ch() expression there…


Thanks a lot!

San