[GEM-dev] How to change perspective Angle in Gem : WAS gemwin "view" message

B. Bogart ben at ekran.org
Mon Apr 3 21:31:29 CEST 2006


hi Cyrille,

Thanks!

seems a little obvious now, I think I was trying to change the perspective
angle by trying to move the Z planes, not the XY planes!

So the question is:

I know what angle I need, or what size and position I want the gemwin to
be, but I don't know how to map this to the units of perspec.

What do the perspec units mean?

I'll keep messing around...

Thanks for the tip!

.b.

On Mon, April 3, 2006 3:06 pm, cyrille henry said:
> hello,
>
> i think you should use more the perspect message than the view message.
>
> try by example :
> perspect 0 2 -1 1 1 20
> and
> perspect -2 0 -1 1 1 20
> to create 2 screens that perfectilly connected.
>
> you can also try :
> perspect  0 $1 -1 1 1 20
> to adjust the lens...
>
> Cyrille
>
>
>
> B. Bogart a écrit :
>> Hey all,
>>
>> Anyhow I tried another approach to my setup so that all the three
>> virtual
>> cameras require the same lens, but alas it still does not work since the
>> default lens of the camera does not match what I would like.
>>
>> A quick run down of what I'm doing:
>>
>> I have a (physical) space with three rear-projection screens. I want to
>> have three gemwins (on different machines) that each sees the gemworld
>> from the view of each of these physical screens. They are fixed in
>> space,
>> surrounding a room at angles (see attached filen which shows the view of
>> the room from the top). Basically the virtual gem-space is then mapped
>> into the physical space on multiple screens. (cave-like, but of course
>> not
>> a cube of screens)
>>
>> So its easy enough to get the camera to point at the center of each
>> virtual screen, but the edges of the screen don't match the edges of the
>> gemwin. (in the attached OOo diagram we should see only the red square
>> in
>> screen 2, and the green square in screen 3, but both the red and green
>> squares are visible in both screen 2 and screen 3.
>>
>> Method-A and Method-B slides show the two options for the camera views,
>> in
>> option A the camera plane is parallel to the screen plane, but the
>> distances  from camera to screen are different. In method-B the camera
>> is
>> the same distance from all the screens, but for screen 2 and 3 the
>> camera
>> plane is not parallel to the screen plane.
>>
>> Also I included a few attached patches:
>>
>> virtual-camera-test2 is method-A
>> virtual-camera-test3 is method-B.
>>
>> I'd really like to get this resolved, since we're hoping to do many
>> gem-projects in this space with these three screens...
>>
>> Thanks all,
>> .b.
>>
>>
>>
>>
>>
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