Help needed -compression, xrel, yrel

[chrisgrant]

Can anyone please explain what the compression, xrel, yrel properties
of a regular (non-pseudo) sprite mean?
I've checked through the Graphics forum and I've read through WIKI
but still have no idea. Other than that I'm getting the hang of NFO files
and everthing seems to work, but when my sprites appear in the game
weird and wonderful things happen!
Any help would be much appreciated.

[BobDendry]

Hmmm...
Xrel and Yrel are determined by a base equation of Xrel=-Xsize/2 and Yrel=-ysize/2 respectively.
Compression is how many pixels shorter the mdoel is, i think. not sure about it.

[DaleStan]

x/yrel define how far right and down[0] to move the sprite before drawing it. Another way of putting this is that x/yrel define the "center" of the sprite--the point the sprite rotates around. This may or may not actually be at the center of the sprite rectangle.

compression is poorly understood; check about two thirds of the way down the Action 1 page for what we do know about its meaning. Set it to one of 01, 03, 09, or 0B. I almost always use 01.

[0] Hence the negative numbers, usually you want to move the sprites left and up instead.

[Siema]

See also:

Format of a GRF file

EDIT: Thing is quite easy: for vehicle sprites in views '_' '|' compression is 01 and for views '\' '/' it is 09. yrel and xrel is ysize/-2 and xsize/-2, as WhiteHand wrote, but mostly you must figure out by trying which position is good (look good in game).

and pic by eis_os:

(edit by eis_os)
Look here: http://www.tt-forums.net/viewtopic.php?t=8083 It would be nice if people would look before reattaching the same thing several times, thanks...

Sorry for that...

[Korenn]

as a guideline for compression, I use the same compression as used in the original ttd files for a comparable sprite.

that way you don't have to know how it works

[eis_os]

Useing undefined compression code can result in breakage of TTD, so use only the ones TTD (trg1) use for the sprite type you are creating

[chrisgrant]

Thanks for the tips. I think 've got the basics of NFO's figured out, so now
all I have to do is come up with some decent graphics and I can post my vehicle in the newbie thread.