Let's say you have a classic particle (not an nParticle) which will use a ramp to assign it's radiusPP.
You want to add some variation to the ramp but have each particle read a unique value and then travel up the ramp over it's lifespan as usual.
Here are the steps:
1. Create the radiusPP via the Add Dynamics Attibutes button
2. Create the ramp by right-clicking in the RadiusPP box
3. Right-click the RadiusPP box again and hold over the menu item until the second menu appears. Choose Create RadiusUPP
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgzXRwGLkz-PLmsOZAsa7xxA5ZhohvGtlWjEbCpYCIbWnvGxy1qz5SW4p09LVDlUUGPlY80LSKpimvYy5pM_MkE4zEn_kfHGH5Iwu4Q62g01mDG_s5KyAg26lV2_ERyUcRXXJxeyJ_o_iED/s320/radiusUPP_01.jpg)
4. Once you have the RadiusUPP attribute, give it a random value betweek 0 and 1 via the expression editor
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg6OWxm75zxoDKDOzNg_2ktcAaBZXNpFuyfOzUrlrziKJWdzuqZOgNQsdj4I8B0HjpuwkVAZOAI1nY95Jj1xUSsL02VqGr6mBDqEPyqLRYPZZ2up4IFwXu7p7mGaZHqBk9UyjO9iHKrzJhK/s320/radiusUPP_02.jpg)
5. To link the UPP value to the ramp, we need to re-make the array mapper. Right-click on the RadiusPP box and delete the arrap mapper (you will want to rename or check the name of the ramp before you do this)
6. Right-click in the RadiusPP box again and click on the Create Ramp options box. Choose RadiusUPP for the input U, leave input V as Particle's Age and then choose the ramp in the Map To list.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhKOA_Fl4qkiGuk3anQuRuT4Fphq3kCoV-9ten7LutuQRhzV9zUSIHATt3_0W68IktJ_HDPI2FJ3Iw490btfFV_KGQgrvHvDf9JaJFNehjKllXpVXoeIlzOzchqW8nstQEXkIr2LjTVdsDV/s320/radiusUPP_03.jpg)
Now each particle is going to read a value at a random point across the bottom of the ramp and then move up the ramp over it's lifetime. Now we need to add some variation to the ramp. A quick way to do this is to use the ramp's built in noise functions
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg3rpD4F06oGbSDF541Y_WKuRa7GiU7isu8cPGHEzpfvDImfaKWN-gFitdNaTlGb-L_CGVrgoQ6KZfV3G_IJo_1oVVaEf8vYKIxUczloWfGNxkydm5kcVBjcNrgXD_88nBI3HAg1h_Lfg99/s320/radiusUPP_04.jpg)
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