ELI5: Explain Like I'm 5

Projection plane

Have you ever drawn a picture on a piece of paper or a whiteboard? Did you notice that your drawing looks flat, like it's on a flat surface? That's because you drew it on a projection plane!

A projection plane is like a special surface where things can be projected onto. When we draw or take pictures of 3D objects, we need to flatten them onto a 2D surface so we can see them properly. This is done by projecting the 3D object onto the projection plane.

To give you an example, imagine you have a toy car that you want to draw. If you look at the toy car from the side and draw it on a piece of paper, you are essentially projecting the toy car onto the paper. The paper is your projection plane!

The projection plane is usually a flat surface like a piece of paper or a screen, and it is usually perpendicular (straight up) to a line of sight. This line of sight is like an imaginary line that connects your eyes to the object you are looking at.

When we project the object onto the projection plane, it can result in different types of projections. For example, a perspective projection looks like what we see in real life, while an orthographic projection looks like a technical drawing.

Projection planes are used in a lot of different fields like architecture, engineering, and art. They help us see 3D objects in 2D spaces so we can understand them better.
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