# RealFlow Wisdom

## How to calculate the radius of a particle?

Now in RF5 you can add user attributes to the particles to use in render process, for instance the radius. To calculate you need at least the resolution of the emitter.

`r = 1 / ( 10 x rEmit ^( 1 / 3 ) )`

where:

rEmit is the resolution of the emitter

February 15, 2010

## How to create swell using expresions?

In scenes where you need to simulate shore waves, crest waves or simply breaking waves against the coast or cliffs, it is very useful the use of expressions. Expressions can be added to the  most node attributes  in RealFlow, using them to add cadence of movement or variability.

Imagine we are trying to simulate the coast where waves break against the rocks. You need to move the water or create a similar ocean movement.  Have a look to next video for better understanding of what I mean.

In this set up I used an expression to control the cadence of the waves. Maths are not my forte, 🙂 sorry,  so I´ll try to explain how works the expression I´ve used:

Given the expression

`a*(1-sqrt(tanh(b*(sin(t/c)^2))))`

where:

a was the Force Amplitude that will give the Wave Height

b was the sharpness of the pulse

c was the frequency of the pulse that will produce the Wavelength

This give you a force that produce a wave with a natural cadence. This is not a physically correct formula, if you want to know more about oceans have a look to internet, is full of articles about this field, these ar some of them:

http://en.wikipedia.org/wiki/Wind_wave

February 8, 2010 Posted by | Animaton | , , | 4 Comments

## Visualizing forces from Daemons. 