Drawing something (a line) on top of an OpenGlSurface image

I am using the OpenGlSurface control. At certain moment I have a complex image (it took some time to render) and I’d like to draw something (imagine a line) on top of the current image.

If I have to render everything plus the new line again it will take too much time.

Is it a way of drawing something on top of the image?

I though about using the current image as a background and draw on top of it.

But perhaps there is something much simpler to do.

Any help will be welcome

i think because it use double buffer every call to Render
will paint into something new and then this buffer get visible.

can you use Me.MouseCursor = System.Cursors.Wait ?

Thank you very much for your reply…
Yes the cursor works normally over an image on a OpenGLSurface and I’ve made same tests capturing this image in a picture, but I find weird not being able to draw easily something on top of what is displayed. That’s why I have asked the forum.

have you tried what happens if you call render and draw only a 3d line?

On the macOS, you can force layer-backed views, then place a canvas over the top of the OpenGLView and draw what-ever the fudge you want.

It’s how I draw guides in HDRtist NX.