# r2y

## Syntax

`int r2y(int d, int m)`

## Arguments

**d**
- An integer value for the 'direction' of a pixel.

**m**
- An integer value for the 'magnitude' of a pixel.

## Return

- An integer giving the cartesian y coordinate for the pixel whose polar coordinates are [d,m].

## Description

- Pixels are usually addressed by their cartesian coordinates [x,y], but FilterMeister also allows the use of polar coordinates, and provides a set of functions for conversion between the two systems. Polar coordinates are expressed as [d,m], where 'd' represents the 'direction' to the pixel from the image's center point, and 'm' is the 'magnitude' of the distance from the center. The r2y() function takes a pair of polar coordinates as arguments, and returns the cartesian y coordinate of the corresponding pixel.

## Example

%ffp
ForEveryTile:
{
int centerX = 100; // distances from the top left corner of the image
int centerY = 100;
int radius = 50;
int angle = 360;
int thd; // angle in degrees
int thk; // angle from -511 to 512
for (thk=0; thk<=angle; thk++) {
thd = (-thk * 1024)/360;
if (thd < -511)
thd += 1024;
for (z=0; z<Z; z++)
pset(r2x(thd, radius) + centerX, r2y(thd, radius) + centerY, z, 0);
}
return true;
}

## Also see

- c2d,c2m,r2x

## Comments

- Everyone can add his comments about his experiences with this function here. Tips for using it are welcome, too.