OpenGL / C++ - How do you fill an area surrounding a point on a mouse click?

Question

Hi all,
I've got the mouseclick handler correctly set up. I have a drawing with some shapes. Is there any way for me to fill the surrounding part of a point until it hits a polygon boundary. Something like Microsoft Paint's "fill" command.

Thanks!

Answer 1

Using opengl? I seriously doubt that ... What you can do ist to detect the shape selected by the mouse click and draw this shape in a different color.

Answer 2

Consider using OpenGL selection capabilities with glSelectBuffer.
Refer to this chapter of the red book for explanation.

Answer 3

What you're looking for is called a Flood Fill and it's a per-pixel algorithm; which means you're going to want to look at either Frame buffer objects with shaders or use the (very slow) glDrawPixels.

Answer 4

The advice to use glSelectBuffer is pretty good. Once you've read that chapter, however, look for the "Now that you know" chapter, and look for a section named "Object Selection Using the Back Buffer" -- it's a lot simpler, and usually entirely adequate.