Lookup in VOP spline ramp

[loudsubs]

I'm trying to create an effect with some boxes copied onto particles and scale the copies using the life attribute. The trick is, I want the scale of each box to start at zero, then grow to one about midway through the particle's life, then scale back down to zero before dying.

I was able to accomplish this using the color pop with a lookup of $LIFE, and then stamping $CR into the scale of each box being copied.

Purely for learning purposes, I'm trying to do the exact same thing in SOPS using a vopsop spline ramp to control the scale using the life attribute as a "lookup". Creating an attribute out of this and using the point ID, and then stamping it to each copy.

I'm really just trying to figure out how to make a lookup input for a spline ramp, similar to the color pop.

I've attached my hip file. The "first try" object shows what I'm trying to accomplish, the "2nd try" obj is where I'm stuck using vops.

Thanks in advance for any advice

pop_box.hipnc

[mightcouldb1]

The life attribute in a vop sop is not normalized. You will have to use age/life and feed that into the ramp lookup. All you have to do after that is multiply a scalar value by the spline ramp output. If you multiply the values, you can have a scale of 40 when the ramp is at 1 and so on.

[mawi]

I'm trying to create an effect with some boxes copied onto particles and scale the copies using the life attribute. The trick is, I want the scale of each box to start at zero, then grow to one about midway through the particle's life, then scale back down to zero before dying.

I was able to accomplish this using the color pop with a lookup of $LIFE, and then stamping $CR into the scale of each box being copied.

Purely for learning purposes, I'm trying to do the exact same thing in SOPS using a vopsop spline ramp to control the scale using the life attribute as a "lookup". Creating an attribute out of this and using the point ID, and then stamping it to each copy.

I'm really just trying to figure out how to make a lookup input for a spline ramp, similar to the color pop.

I've attached my hip file. The "first try" object shows what I'm trying to accomplish, the "2nd try" obj is where I'm stuck using vops.

Thanks in advance for any advice

In SOP land you can divide Global Life by Age to get a value 0-1 over life.

Also, the copy-SOP will catch the attributes pscale, rot and orient so you dont have to stamp them.

http://www.sidefx.com/docs/houdini11.0/copy/instanceattrs

At the moment my son is in my knee watching Pingu so i really cant make you an example.

Edit: Late as always.

Edited September 11, 2010 by mawi

[loudsubs]

thnx guys, age divided by life did the trick.