Thread: Is there an example of picking objects using mouse?

Hey guys,

I was just wondering if there's an example of picking and dropping objects using mouse in OpenGL? The tutorial # 32 on Nehe isn't that helpful. I know how to rotate an object or zoom etc. using mouse which i learned from Nehe tutorial # 48 and others. However, i couldn't find a good example of how to pick an object and then drop or even better if one could move an object (means translate from one spot to another) using mouse. Any example or ideas would be apperciated. Thanks in advance!!

>> how to pick an object and then drop or even better if one could move an object

The term "picking" in 3D graphics means determining which object (in 3-space) the mouse was pointing at when it was clicked. This is what NeHe's tutorial describes.

Moving the object (or picking it up in plain english terms) is just a matter of translating the selected (picked) object by the amount that the mouse moves.

1. Get the screen coordinates of where the user clicked.

2. Convert those coords to the coordinate system you're using when you draw (may not be needed)

3. Multiply that by camera frame/matrix/orientation/however you like to call it as well as your projection matrix

4. That point and the camera position create a ray for you to use in order to find out what object they clicked.

Give here a spin, and let us know how it goes.