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

Chris Hanson xenon at alphapixel.com
Tue Sep 11 12:35:39 PDT 2018

I think some parts were lost in translation. I think the word you want to
use is "eraser" instead of "rubber", though I can see how it could be
mistranslated from another language.

I can think of a way to do this with your current draw order (black line
then green line) by using a shader and a texture holding the background

Otherwise, you'd have to probably change the draw order so that the black
line was drawn later than the green line.

I often recommend users with complex questions "take a step back" and
explain the non-simple-abstract problem. Many times we find people asking a
specific question believing it is the only solution, and finding no good
ways to achieve it, when in fact the same overall goal could easily be
accomplished a different way if we knew what they were really trying to do.

Could you explain more about the real-world problem you're trying to solve,
instead of this simplified abstract summary?

As an example, imagine if someone came to you asking how to safely operate
a flamethrower in their kitchen, and you answered it was impossible. Later
you found out that all they wanted to do was make tea, but had pre-decided
on "flamethrower" as the way to get there, but if they'd just said "I want
to make tea", an electric kettle would have neatly solved the problem.
Don't be the flamethrower tea guy.

On Tue, Sep 11, 2018 at 6:08 PM Christoph Dohmen <christoph.dohmen at cae.de>

> 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.
> I hope that clarified it a bit more?!
> Thank you!
> Cheers,
> Christoph
> ------------------
> Read this topic online here:
> http://forum.openscenegraph.org/viewtopic.php?p=74709#74709
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