Hi Steve,
On 6 June 2018 at 03:42, Steve Hardy <[email protected]> wrote:
> Problems remaining:
>
> 1. the aspect ratio does not adjust properly on window size changes, so that
> the scene just stretches like rubber.
> ....
> For (1), I was assuming that
>
> camera->setViewport(new osg::Viewport(0,0,width,height));
> camera->setProjectionMatrixAsPerspective(30.0f, 1.*width/height, 1.0f,
> 10000.0f);
>
> on the slave and main (?) cameras would fix that up, but no. Maybe there's
> something cached somewhere, even though I am completely reconstructing the
> slave camera on each resize.
>
> Any suggestions where to look?
>
In osg::Camera there is support for adjusting the projection matrix to
track changes in he viewport:
enum ProjectionResizePolicy
{
FIXED, /**< Keep the projection matrix fixed, despite
window resizes.*/
HORIZONTAL, /**< Adjust the HORIZONTAL field of view on
window resizes.*/
VERTICAL /**< Adjust the VERTICAL field of view on window resizes.*/
};
/** Set the policy used to determine if and how the projection
matrix should be adjusted on window resizes. */
inline void setProjectionResizePolicy(ProjectionResizePolicy
policy) { _projectionResizePolicy = policy; }
/** Get the policy used to determine if and how the projection
matrix should be adjusted on window resizes. */
inline ProjectionResizePolicy getProjectionResizePolicy()
const { return _projectionResizePolicy; }
> 2. there is a truly horrendous amount of copying data.
> ....
> For (2), after the hardware renders the scene, and the PBO is mapped back
> into userspace RAM, the following copies occur:
>
> - memcpy to the osg::Image data
> - image->flipVertical() since 2D library has Y inverted w.r.t GL.
> - copy to a new Python string object
> - copy to a new GdkPixbuf object
> - copy to the cairo context (that's the Gtk 2D graphics engine).
To avoid the flip you could flip the projection matrices y axis so
that the it renders upside down,
> I think a lot of this could be eliminated by creating the GdkPixbuf directly
> from the PBO map, flipping the row order in this copy. Although it performs
> OK, we have to run on low-end systems.
Another approach might be to look at trying to use a GL context for
the actual window and see if you can keep the data resident in
graphics memory and copy it across without doing the round trip to the
CPU.
Robert.
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