Do Skew + perspective transform on a rectangle and then check if a mouse cursor is on it

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Mouse picking 3D objects

Inspired by this post, find here a program to detect which 3D object is under the mouse cursor. The idea is to do two render passes. One of them is what the user sees. The other render pass is used internally. It contains the same geometry, but the shapes have been rendered with flat and known colors. Later, we sample the pixel color under the mouse position and use that color to identify the shape under the mouse. In this simple example I’m using the red component of the pixel. Since we use t…