complementing thetha is azimuth and zenith is the other angle...
On Sun, Jul 6, 2008 at 1:05 PM, Pablo Carneiro Elias <[EMAIL PROTECTED]>
wrote:
> Jung,
> the mapping from world to screen is always possible within the camera's
> frustum, but the inverse is not true. It means that not every pixel of the
> screen has a map into world coordinates. Even if a point within the screen
> coordinates has a world mapping point, you can't actually know exactly which
> point it is if you don't constrain the Z value of the point in world. Thats
> because infinity points in world can map to a same point within the screen
> coordinate. So, if you're trying to make some sort of "Arcball" or Trackball
> feature using screen coordinates I can say that you don't need to convert
> those screen point into world points.. you just need a map from screen space
> to a open ball in R^3 using (centered at origin 0,0,0), for example,
> spherical coordinates (two angles)....
>
> to map from x,y into two angles (azimuth and zenith) you can do something
> like this:
>
>
> azimuth = ( 2*( x / screen_width ) - 1 ) * PI
> zenith = ( 2*( y / screen_height ) - 1 ) * (PI / 2)
>
> I've just came up with this mapping now, the're are many ways to build a
> trackball feature, thats just only an idea... to map the two angles above
> into a world vector within the open ball you can use:
>
> where r is an arbitrary ray of the ball (the biggest the ray the smallest
> is the rotation sensitivity)
>
>
> Hope it helps....
>
>
> On Sat, Jul 5, 2008 at 3:06 AM, Jung Lee <[EMAIL PROTECTED]> wrote:
>
>> Dear OpenSG Users,
>>
>> I found most of the solutions for my problems with OpenSG in this user
>> forum! Thank you!
>> However, there is one thing still couldn't find a way - how to convert
>> 2D mouse coordinates into OpenSG world coordinates. Pablo helped me
>> understand it, but I couldn't implement it yet. I found there was one
>> method which translate the world coordinates into screen coordinates
>> in OpenSG (getWorldtoScreen). My questions is that there exists sort
>> of getScreentoWorld function in OpenSG. If not, how can I convert
>> mouse's x,y coordinates into world coordinates (x, y, z)?
>>
>> Thank you always!
>>
>> Jung
>>
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