# Code Snippets

## Rotating 360 degrees NonPhys

Awhile ago I stumbled upon Slerp, and I wanted to make a way to generate a list of rotations for doing a complete rotation.

### First Trial

(this is some of the UGLIEST code I have ever written, but it seems to work. Do not rely on it if you need precision.) <lsl> list GenerateRotationList(integer num) {

```   list RotationList = [];
rotation a = ZERO_ROTATION;
rotation b = llEuler2Rot(<0,0,180> * DEG_TO_RAD );
float interval = 2 / (float) num;
float i = interval;
for(; i <= 1; i += interval)
RotationList += slerp(a,b,i);

if(num % 2)
i = 1 - i + interval;
else
i = interval;
b = llEuler2Rot(<0,0,180.001> * DEG_TO_RAD );
for(; i <= 1; i += interval)
RotationList += slerp(b,a,i);
return RotationList;
```

} </lsl>

### Common Sense Prevails

After a little debating it hit me that their is no point in calculating the individual positions if it starts with the same origin every time, doh. So now we have a function that is much cleaner and is a bit more understandable.

<lsl> list GenerateRotationList(integer num) {

```   list RotationList = [];
float increment = 360 / (float) num;
vector Rot = <0,0,0>;
while(~--num)
RotationList += llEuler2Rot( (Rot += <0,0,increment>) * DEG_TO_RAD );
return RotationList;
```

} </lsl>

## SLURL Raster Image URL Generator

I was rather interested in the raster images provided within SL and SLURL.com so I decided to figure out how to replicate it in such a way that it could be incorporated into tools and/or services outside the standard fair offered by Linden Labs. At some point I may rewrite it to use PHP or offer tips to incorporate it into something like the WMS provider in MapGuide.

### PseudoCode

```
//grab the region coordinates and store them
\$RegionPos;

//1 Tile = 256m
\$TilePos = \$RegionPos/256.0;

//Fix the offset in the service
\$TilePos.y = 1279.0 - \$TilePos.y;

//genrate the URL, the 0 on the end may be a switch for gif/png, need to read up more on the SL map API
\$mapURL = "http://secondlife.com/apps/mapapi/grid/map_image/" \
+ Floor(\$TilePos.x) + "-" + Floor(\$TilePos.y) + "-1-0"
```

### LSL

<lsl> //SLURL Tile URL Generator - By Kerik Rau

//Based on the javascript from SLURL.com, merely an adaptation in LSL //It should only take a minute or 2 to export this into PHP or other languages

//SLURL uses WMS, I still want to look at incorporating it into something like Mapguide //I will need to look at the implementation to see if this would be easy or a pain

vector genTileVec(vector RegPos) {

```   //tiles are in a grid based on the regions, so 256m = 1 tile
RegPos /= 256.0;

//offset provided in the javascript, really 1278 + 1 (probably 0 -> 1 index difference?)
RegPos.y = 1279.0 - RegPos.y;
```
```   return RegPos;
```

}

string genMapURL() {

```   vector TilePos = genTileVec(llGetRegionCorner());

//should look like http://secondlife.com/apps/mapapi/grid/map_image/x-y-zoom-0
string mapURL = "http://secondlife.com/apps/mapapi/grid/map_image/";
mapURL += (string) llFloor(TilePos.x);
mapURL += "-";
mapURL += (string) llFloor(TilePos.y);

//the 3rd value is something to do with zoom, but only 1 seems to work with this
//the 4th value is undefined, omitting it works but I leave it in to match SLURL
mapURL += "-1-0";
return mapURL;
```

}

default {

```   state_entry()
{
llSetText("SLURL Raster Image URL Generator\nOpens the image of the current sim\n(in a browser)", <1,1,1>, 1);
}

touch_start(integer numdet)
{
integer i;
for(i = 0; i < numdet; ++i)

}
```

}

</lsl>

# Running SL Cahce in Linux RamDisk

## General Idea

Fedora generates 16, 16MB ramdisks upon bootup that are not in use. Basically my idea is to use Linux's LVM to initialize and span these drives together automatically and mount it to the location of SLs rather ugly cache to improve speed.

## Issues

• Parted doesn't recognize the ramdisks (/dev/ram0 -> /dev/ram15) as a drive and refuses to open it.
• cfdisk doesn't seem to be useful outside of the interactive shell
• fdisk requires a user to manually do the job, yuk
• sfdisk seems to be solution but it is rather ugly
• Using LVM to span the drives may have performance implications
• The data in the partition will be lost every time the machine shuts down

## Workflow

• Format each drive to type 8e (Linux LVM)
• Add the drives into a spanning group
• Format the LVM group with an EXT2 partition (with "-m 0" so no space is reserved for root)
• mount the partition to the ~/.secondlife/cache directory

## TODO

• Get around to working with sfdisk and finish writing the INIT script