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What is the logic to having an axis labeled Z and also having Z refer to distance from the camera? It seems like an easy way to confuse people. Is this due to the conjunction of two different lexicons, one from geometry where they have a Z axis and one from photography?

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Quoting from iKlsR's answer:

Blender uses the right hand coordinate system with the Z axis pointing upwards. This is common with the coordinate systems used by most common 3D CAD packages.

However, it's also a standard to use Y up for images (with Z as depth).

To help with getting used to it, you could try a couple things:

  • Imagine you are looking at the image editor top down instead of from the side.

  • Think in terms of the camera's local coordinates (the local Z is always out the front)

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In blender Z is up in world space. In the camera Z is also the distance from the camera. There are many cases where the Z axis are not the same and could potentially confuse you. In this image the object is upside down. In world space Z would be pointing up. In local space it is pointing down.

enter image description here

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When referring to the camera, 'z' is typically the depth buffer.

This used for is determining which objects are in front of other objects and is used to determine what should be drawn.

Without a z-buffer, your GPU would have to draw things based on the order that objects are submitted by the OpenGL or DirectX draw calls instead of drawing based on what fragments(pixels) are closest.

I'm sure that there are many other uses for the z-buffer in Blender or other 3D software.

For instance, you can use the z-buffer(distance to camera) for LOD(level of detail). When an object moves further away from the camera then you can swap it for a model that has less detail and you can switch to a shader that requires less rendering power.

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