[PD] GEM mapping units to pixels

[altern]

cyrille henry(e)k dio:
> hello,
> 
> altern a écrit :
>> hi
>>
>> do you mean something like the example attached?
> yes, exactly.
> 
>> This doesnt work ok for me, the shape should be 10x10 px and is not, 
> a [rectangle 10 10] should be 20 pixel.

i understand from the rectangle help that [rectangle 10 10] should be a 
10 units width by 10 units height square. I get a rectangle which is 
irregular, check the attached screnshot gif

>> also x and y pos are dont match with window size. Translating to 400, 
>> 300 should place the rect in top right corner but I get that with only 
>> 320, 190,  so the units are not mapped to pixels
> translating to 400 300 should move the center of the rectangle in the 
> top right corner.
> if your rectangle is 100 100, then you just have to move it 300 200 in 
> order to have the corner of the rectangle in the corner of the gem window.
> 
> your patch work that way here.

check the attachment again, the rect is 10x10 and it is located at 
X=307, Y=167. This should be far from 400, 300 which should be the 
top,right location. So the coordinate system is distorted, specially on 
the y axis

I also tried with
dimen 400 400
perspec 0 400 0 400 999 1001
If draw a 1 by 1 rect and i get it to the right top corner by 
translating it 320, 320. So pixels are dont match gl units and moreover 
in the previous example when the gem window is not a square the 
distortion affects differently the X and the Y axis

>>
>> but maybe i am missing something from what you describe?
>>
>> In opengl to achieve this 2D like-pixels to units effect i would
>> set the perspective to be orthographical with glOrtho command, is 
>> something like this possible in Gem?
> yes, insert an [ortho] after the gemhead
> 
> 
> cyrille
> 
>>
>> thanks!!
>>
>> enrike
>>
>> cyrille henry(e)k dio:
>>> hello,
>>>
>>> i tried with :
>>> dimen 400 300
>>> view 0 0 1000 // 1000 is in order to put the camera far from the view 
>>> point, to reduce space distortion
>>> perspec 0 400 0 300 999 1001 // 999 and 1001 limit the render to 
>>> primitive position is between -1 and 1 (because camera is at 1000)
>>>
>>>
>>> and everything is working as expected.
>>> i just have 1 strange thing : i need to set the [dimen<, [create<  , 
>>> then [reset< and last [view< and [perspec< if i did not do a reset, a 
>>> square is not rendered as a square but a rectangle.
>>>
>>> anyway, it's working.
>>>
>>> cyrille
>>>
>>>
>>> altern a écrit :
>>>> i tried to pass different view values to gemwin. I can see that in 
>>>> order to be able to specify location or with with pixels i should 
>>>> set view to
>>>> view 0 0 2
>>>> but as soon as i set that the shape is not there any more. This is 
>>>> an example i am using to test. If i ser view to
>>>> view 0 0 2.01
>>>> it is almost there but if i set it to 0 0 2 it is not there any 
>>>> more. I guess it might be because it is either beyond the back limit 
>>>> y or behind the camera?
>>>>
>>>> thanks
>>>>
>>>> enrike
>>>>
>>>>
>>>> altern(e)k dio:
>>>>> hi
>>>>>
>>>>> I am trying to map GEM units to pixels so that i can position some
>>>>> videos in the GEM window using pixels values. For this I understand 
>>>>> that
>>>>> i must match the projection values with the window size. So i am doing
>>>>>
>>>>> dimen 400 300
>>>>> perspect 0 400 0 300 1 20
>>>>>
>>>>> and i render all objects at z position 1
>>>>>
>>>>> translateXYZ 100 100 1
>>>>>
>>>>> However I am getting a weird result, the units are far smaller that
>>>>> pixels, so to move a video 100px in the x i need to change it x 
>>>>> position
>>>>> by 300 units or something like this. So I am not sure about what i am
>>>>> doing wrong, I am familiar with OpenGL but i never played too much 
>>>>> with
>>>>> GEM before so I am still getting into it.
>>>>>
>>>>> Another small issue is that I would also like to reverse the Y so that
>>>>> upper left is 0,0 and bottom left would be 0,200 for example, not sure
>>>>> about how to change this. I guess it is to do with the gemwin settings
>>>>> but i dont get it right.
>>>>>
>>>>> thanks
>>>>>
>>>>> enrike
>>>>>
>>>>>
>>>>
>>>>
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>>>>
>>>>
>>>
>>
>>
>>
>> ------------------------------------------------------------------------
>>
>> #N canvas 393 156 429 320 10;
>> #X obj 84 210 gemwin;
>> #X obj 245 163 gemhead;
>> #X msg 173 82 create \, 1;
>> #X msg 293 106 0 \, destroy;
>> #X floatatom 309 164 5 0 0 0 - - -;
>> #X floatatom 347 164 5 0 0 0 - - -;
>> #X floatatom 288 215 5 0 0 0 - - -;
>> #X floatatom 332 215 5 0 0 0 - - -;
>> #X obj 245 190 translateXYZ 10 10 1;
>> #X msg 215 50 dimen 400 300;
>> #X msg 48 73 view 0 0 1000;
>> #X msg 9 48 perspec 0 400 0 300 999 1001;
>> #X msg 110 99 reset;
>> #X obj 50 -8 bng 15 250 50 0 empty empty empty 0 -6 0 10 -262144 -1
>> -1;
>> #X obj 50 13 t b b b b b;
>> #X obj 245 234 rectangle 10 10;
>> #X connect 1 0 8 0;
>> #X connect 2 0 0 0;
>> #X connect 3 0 0 0;
>> #X connect 4 0 8 1;
>> #X connect 5 0 8 2;
>> #X connect 6 0 15 1;
>> #X connect 7 0 15 2;
>> #X connect 8 0 15 0;
>> #X connect 9 0 0 0;
>> #X connect 10 0 0 0;
>> #X connect 11 0 0 0;
>> #X connect 12 0 0 0;
>> #X connect 13 0 14 0;
>> #X connect 14 0 11 0;
>> #X connect 14 1 10 0;
>> #X connect 14 2 12 0;
>> #X connect 14 3 2 0;
>> #X connect 14 4 9 0;
>>
> 

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