[osg-users] Read number of Pixels an object takes up

[Ulrich Hertlein]

Hi Paul,

On 3/7/09 5:57 PM, Paul Martz wrote:
>   Ulrich Hertlein wrote:
>> While we're on the subject: for simple objects, say a sphere or an
>> AABB, shouldn't it be possible to do this calculation quicker on the
>> CPU without going to the GPU? Isn't something like this done for small
>> feature culling?
> Host computation has (by definition) no access to the depth buffer.

Certainly not.  Sorry, I should've been clearer.

What I'm basically after is "how big (in pixels) is this box/sphere in screen space" 
without taking occlusion, clipping, or such into account.  Given projection and modelview 
matrix that should be doable, right?

Cheers,
/ulrich