[Sidefx-houdini-list] Spare ramp param question

Stephen Tucker stucker at allegrodigital.com
Tue Jul 20 18:50:50 EDT 2010


ramps map values between 0 and 1,
so for example if you wanted to map the Alpha of a particle over it's lifespan, in a point sop you could use:

chramp("rampparameter", $LIFE, 0)

where:
- rampparameter is the path to your ramp parameteter
- $LIFE is the normalized age/lifespan attribute that you get for free with particles
- 0 is the index of the ramp (rgb = 0,1,2)

If you want it to map with Time, which maps between 0 and 1 over the course of the first second and afterward will give you bogus values as far as your ramp is concerned... you need to find a way of normalizing your time to be in the range of 0 to 1, by using another expression such as $T/$TEND as your seed.

Hope that helps




> From: alex at franktheplumber.com
> To: sidefx-houdini-list at sidefx.com
> Date: Tue, 20 Jul 2010 22:41:01 +0000
> Subject: Re: [Sidefx-houdini-list] Spare ramp param question
> 
> Thanks Steve and Alex, that was quick!
> I guess my question might not be as simple as I thought...I was under the
> impression I could simply refer the External Force to the Ramp, and it would
> evaluate it over time..But it looks like chramp() only takes one particular
> position on the given Ramp?
> 
> Thanks
> Alex
> 
> 
> On 7/20/10 3:31 PM, "Alex Lim" <list at poh-yee.com> wrote:
> 
> > Hi Alex. Perhaps chramp() is what you're after?
> > 
> > Cheers, Alex
> > 
> > 
> > 
> > On 7/20/2010 3:28 PM, Alex Czetwertynski wrote:
> >> Hello
> >> 
> >> I'm trying to create a simple channel reference to a spare ramp param I
> >> created in a POP SOP.  I basically am linking the External Force to a ramp I
> >> created and using ch("./myramp") in the Y value of the External Force.
> >> What I can see is that the value I'm getting out of that is 2, which I
> >> assume it is getting from the number of points in my ramp, not the ramp
> >> values....What am I doing wrong?
> >> 
> >> Thanks
> >> Alex
> >> 
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