Polypainting?

[CalciumZero]

Hello I am a student who has been studying C++ for about 9 years (since I was ten)
I work pretty hard but now I have come across a problem. I am trying to write a C++ library for functions to help poly-paint an obj file once rendered in opengl. I usually just look at math and interpret it as a coded version. But I have looked for quite some time but I can't find anything on poly-painting or any examples of it in C++ or any kind of formula really. Is their any basic code out their that I could work with on poly-painting with colors or textures in OpenGL C++? Some help to get me started would be pretty nice!I hope I get help soon.
(Programs like Zbrush and sculptris does this But I'm not sure how)

[CalciumZero]

Hello anyone?
Please I could really use some help!
Also would bullet physics be great for generating tree's from premade models?(Just randomizing the structure)

[Moooce]

I'm not sure, but is it this kind of thing you're trying to do?

http://stackoverflow.com/questions/8803917/realtime-object-painting

Maybe that will point you in the right direction?

[CalciumZero]

Yes actually. I am trying to paint with certain texture patterns on obj files. like if I select the grass texture option wherever i left click and hold down the mouse It would paint a texture within a certain radius and opacity and can be erased later on.(one step at a time though just simple texture painting for now with a fixed radius and full opacity. a bool would represent true then the painting function begins until the mouse is no longer held down. Is there anymore research on this sort of thing though? I am trying to incorporate it into my engine but I'm not really very well understanding the math behind it with just this. But thank you this could come in handy. But I would like to know If anything more in depth could be explained.

[Moooce]

I know less than you about this, but maybe searching google for things like world to texture coordinates or transforms may help you find some code to convert your screen coordinate from the mouse into a texture coordinate of the texture.

[CalciumZero]

Thanks I'll try that and let you know how it goes.
But still if any help comes along I would be glad to know!