[PD] [Gem] changed [ortho] behaviour

Jack jack at rybn.org
Sun Sep 10 23:34:54 CEST 2017

Hello Roman,

Le 10/09/2017 à 22:34, Roman Haefeli a écrit :
> On Sam, 2017-09-09 at 18:50 +0200, cyrille henry wrote:
>> Le 09/09/2017 à 12:44, Roman Haefeli a écrit :
>>> On Sam, 2017-09-09 at 12:37 +0200, cyrille henry wrote:
>>>> hello,
>>>> yes, the ortho was buggy and fixed. But the old behaviours is
>>>> still
>>>> possible if you send a "compat" message.
>>>> See help file.
>>> I see, thanks. I should have checked the help file in the first
>>> place.
>>> But how can someone use the full window area with the new default
>>> mode?
>> changing the windows perspective!!!
>> (using the perspec message to gemwin, see help file)
> Sorry, I don't understand. Maybe I simply don't understand which
> question this answers. 

I guess Cyrille want to say that you can manage the clipping of ortho
with the message 'perspec'. 'perspec' seems to work for the frustum
(with perspective) and ortho (orthographic mode).
I can't test here because, like you in your video, [ortho] not work
properly on my system with a recent Gem (ver: 0.93.git 10759c2).
Using [ortho] on a square in the center of my gemwin, move this square
elsewhere. I can also confirm that message 'compat' do nothing here.

However, you can simulate [ortho] if you need it now with :

[GEMglOrtho -1 1 -1 1 1 20]

With these objects, you reset the projection and use orthographic
projection for your geo. -1 1 -1 1 1 20 are the clipping volume in ortho

Don't forget to use just after your geo (if you want your perspective
come back) :

[GEMglFrustum -1 1 -1 1 1 20]

Hope it helps.


>>> Why is there a limit?
>> what limit?
> What I am experiencing when using [ortho] is that only the lower left
> 500x500 pixels of the gemwin can be used for rendering. Also, the
> center seems to be in the middle of this 500x500px area. This is with
> current master (cc0d464a) on Ubuntu 16.04 with a Intel graphics. Please
> check this screen recording:
> http://netpd.org/~roman/ramsch/ortho_limit.mkv
>> "ortho" change the way objawayect appear smaller far away.
> This I understand. All parallel lines appear parallel in orthographic
> projection. 
>>  It also use to change the perspective and was in conflict with the
>> gemwin "perspec" message.
> This I don't understand.
>> the conflict have been removed.
> I'm a bit confused whether I hit a bug or if there is some big
> misunderstanding on my part. Can you check the above video and tell me
> if you get the same?
> BTW: the 'compat' method does not work for me. No matter whether I send
> 'compat 0' or 'compat 1', the rendered output looks exactly the same.
> Roman
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