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

[cyrille henry]

hello,

i don't understand the question, but :
tan (angle) = size of the window / distance of the camera.
(so, you don't nead unit).

otherwise, a good openGL book with a clear graphic of what exactely 
perspec and view message are is the only thing you nead...

cyrille


B. Bogart a écrit :
> 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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>>
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> 
> 
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