[PD] Gem axis

[Johannes M Zmoelnig]

cyrille henry wrote:
> hello

hi.

just a quick comment, as i believe, from nico's last email, that it is 
not clear why "this works and that does not"

> 
> if
> 
> gemhead
> |
> translate
> |
> rotate
> |
> square
> 
> does not work,

this is *wrong*, it works!!!


> try :
> 
> gemhead
> |
> rotate
> |
> translate
> |
> square
> 

this works "too", but both patches are _different_

> transformation order is important.
> 

this is the magic!


imagine following:
1) you are standing at the "origin"; you turn 90° to the right; you walk 
5 steps forward
2) you are standing at the "origin"; you walk 5 steps forward; you turn 
90° to the right

now think: is the result of 1) and 2) the same ? (this is: after the 2 
"transformations", are you standing at the same spot and are you looking 
in the same direction ?)

this is the way, openGL works


mfg.cas..r
IOhannes