[osg-users] Idea to implement a kind of 'rubber mode'

[Daniel Trstenjak]

Hi Christoph,

On Tue, Sep 11, 2018 at 07:09:26PM +0200, Christoph Dohmen wrote:
> Well, Chris, thanks for the question. It shows that I was not precise
> enough. Currently I'm drawing the black line on top of a quite
> complex background (light blue). And as a second item I draw the quad
> with the red frame showing the green symbol and having transparent
> colour in the background so the scene background hat visible and the
> black line.  My goal is to use the textured quad as a rubber and
> remove the black line but not the scene background like in symbol.png.

are you making some kind of drawing program, and you want to be able
to move the rubber/erasier around and delete the previously drawn lines?

If this is the case, then you most likely don't want to implement the
erasing operation as an OpenGL graphics operation, but as an operation
on your program data describing the lines.

You're modifying the internal program state and then draw this new state.

Greetings,
Daniel