[Csgl-users] obscured control and context.ToImage()

[Aron E. <ar...@se...>]

Hi all,

I'm working on a volume rendering application where rendering a frame might
take several seconds. Because of this, I cache the most recently rendered
image as a bitmap (using context.ToImage()) and in OnPaint() I just draw
this bitmap if it is still valid, instead of rendering the whole scene over.

There seems to be a problem when the Control (which is not an OpenGLControl
but a "standard" control containing a ControlGLContext) is obscured by
another window - there will be rubbish in the obscured parts of the window.
So when the front window is moved and my OnPaint() is called and I draw the
bitmap, the part that was not visible before will contain errors.

The two attached images illustrate what happens. In "bad.jpg", the lower
part of the image was obscured by the Task Manager at rendering time.
"good.jpg" shows what it should look like.

Is there any way I can force the whole control to be redrawn, even if parts
of it are not visible?

Thanks for any help! Best regards

Aron Ernvik