Selection/Picking question---help?

how will selection/picking work for an imported drawing…e.g. i want to slect/pick drawing in my application that was created in another software such as AutoCad or Paint


Define drawing, picking operates on geometry.

If you want to select rendered image portions you would need to render outlines of those selectable portions as geometry.

To pick stuff in a 2D 3D scene, you set the viewport to the pick region, then draw the scene. As you draw the scene you set a unigue hit identifier for each pickable object in the scene. If the objects are visible they will leave a hit code in the pick buffer.