Projection matrix

Imagine you are looking at a picture, but instead of seeing it on a flat piece of paper or screen, you are seeing it on the side of a big box. The box has a special window that lets you look inside and see the picture in 3D, like you are actually there.

But how does the picture get inside the box? That's where the projection matrix comes in. It's like a magic spell or a secret code that takes the picture on the flat paper or screen and turns it into something that can be projected onto the inside of the box.

The projection matrix is a set of rules or instructions that tell the computer how to take the 2D image and make it look like a 3D object inside the box. It uses math and geometry to figure out where each point in the image should go and how big or small it should be to look right inside the box.

So when you look into the box, you are seeing a 3D version of the picture, even though it was originally just a flat image. And that's all thanks to the projection matrix!