Understanding the sprite sheets

[catmorbid]

I've been trying to work out how to add simple animated particles/projectiles, and there's some things I don't understand regarding the .xml file used for the sprite sheet.

Let's take for example the particle greysmoke:

<sequence name="particles/greysmoke/greysmoke.xml" source="./smoke*.png">   <img regx="46" regy="71" name="greysmoke" w="0" h="0" />   <framelist>       <frame regx="47" regy="99" x="191" y="381" w="92" h="126" name="smoke0000.png" xform="1.000000 0.000000 0.000000 1.000000 0.000000 0.000000" />       <frame regx="47" regy="99" x="191" y="508" w="92" h="126" name="smoke0001.png" xform="1 0 0 1 0 0" />       <frame regx="48" regy="99" x="381" y="127" w="93" h="126" name="smoke0002.png" />       <frame regx="48" regy="99" x="475" y="127" w="93" h="126" name="smoke0003.png" />       <frame regx="47" regy="99" x="285" y="254" w="92" h="126" name="smoke0004.png" />       <frame regx="48" regy="99" x="191" y="254" w="93" h="126" name="smoke0005.png" />       <frame regx="48" regy="98" x="475" y="381" w="93" h="125" name="smoke0006.png" />       <frame regx="49" regy="98" x="378" y="254" w="94" h="125" name="smoke0007.png" />       <frame regx="48" regy="98" x="475" y="507" w="93" h="125" name="smoke0008.png" />       <frame regx="49" regy="98" x="473" y="254" w="94" h="125" name="smoke0009.png" />       <frame regx="49" regy="99" x="192" y="0" w="94" h="126" name="smoke0010.png" />       <frame regx="49" regy="98" x="285" y="381" w="94" h="125" name="smoke0011.png" />       <frame regx="49" regy="99" x="287" y="0" w="94" h="126" name="smoke0012.png" />       <frame regx="49" regy="98" x="285" y="507" w="94" h="125" name="smoke0013.png" />       <frame regx="49" regy="98" x="380" y="381" w="94" h="125" name="smoke0014.png" />       <frame regx="49" regy="98" x="380" y="507" w="94" h="125" name="smoke0015.png" />       <frame regx="49" regy="99" x="382" y="0" w="94" h="126" name="smoke0016.png" />       <frame regx="49" regy="99" x="477" y="0" w="94" h="126" name="smoke0017.png" />       <frame regx="49" regy="99" x="96" y="127" w="94" h="126" name="smoke0018.png" />       <frame regx="49" regy="99" x="96" y="254" w="94" h="126" name="smoke0019.png" />       <frame regx="49" regy="99" x="96" y="381" w="94" h="126" name="smoke0020.png" />       <frame regx="50" regy="99" x="0" y="0" w="95" h="126" name="smoke0021.png" />       <frame regx="50" regy="99" x="0" y="127" w="95" h="126" name="smoke0022.png" />       <frame regx="50" regy="99" x="0" y="254" w="95" h="126" name="smoke0023.png" />       <frame regx="50" regy="99" x="0" y="381" w="95" h="126" name="smoke0024.png" />       <frame regx="50" regy="99" x="0" y="508" w="95" h="126" name="smoke0025.png" />       <frame regx="50" regy="99" x="96" y="0" w="95" h="126" name="smoke0026.png" />       <frame regx="49" regy="99" x="96" y="508" w="94" h="126" name="smoke0027.png" />       <frame regx="49" regy="99" x="191" y="127" w="94" h="126" name="smoke0028.png" />       <frame regx="49" regy="99" x="286" y="127" w="94" h="126" name="smoke0029.png" />   </framelist>

Can someone explain what regx and regy do? the x and y seem to be the actual x and y coordinates for the sprite (probably top left) and together with height (h) and width(w) you reasonably have the area around the sprite. But the regx, regy and xform are a mystery to me. If someone has figured this out, I'd appreciate it I know how to get the actual atlas together, I just need to know how to set up the configuration file

[Sentelin]

I believe that regx and regy are registration points of each sprite. (It will take me sometime to right more detail explanation since I am struggling to find words and terms).Nah If I try to explain with my own words it will just get you confused,here is copy/paste explanation from my digital book:

What is a registration point? Do you know what I am talking about? Simply put, a registration point is the default location of an object from which an object's x and y co-ordinates are determined. More simply, it is the crosshair that appears in the center or corners of your object after you convert it into a movie clip, graphic, or button. .

Edited June 28, 2014 by Sentelin

[catmorbid]

Ah, like pivot points. Yes yes, I get it now, thanks!

[Max_Caine]

To expand on Sentelin's comments. regx and regy mark the reference point on the ground combat tile where your smoke will appear. x and y are the lookup point for your particle effect in the spritesheet.

EDIT: Assassinated by the op!

Edited June 28, 2014 by Max_Caine

[Mikhail Ragulin]

It's possible to just point the projectile towards an animation sequence - I just tried it, renaming robbanas\explode to the name of the projectile, and it came out in a fully animated stream of glory.