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### #ActualGuyWithBeard

Posted 19 January 2013 - 10:09 AM

Consider the following scene:

- A parking lot area, the form of a square, with the world space origin in the middle of the parking lot area.
- A bike parked in the northeast corner of the parking lot.
- A camera which someone has left on a bench in the southwest corner of the parking lot.

Both the camera and the bike have their own local spaces, and any position within their local space can be transformed into world space. First consider the bike. If you were to sit on it, the front of the bike would be facing "forward", and back "backward". You would grab the right part of the handlebar with your right hand, etc. All of these things remain the same regardless of where in the world the bike is. Whether it is upside down or lying on the ground. Its local space remains the same.

To tell your game where in the world the bike is, its vertices have to be transformed, "moved to", world space. At this point it matters where the bike is and how it is orientated. If you move the bike from the north east corner to the northwest corner, the world position (and possibly orientation) of the bike seat changes. However, the local position of the seat is still the same (ie. it has not moved in regard to the other parts of the bike).

Now consider the camera. It is not in the same place as the bike, so moving a position from its local space to world space is a different kind of transform, but the idea is the same.

Now, if you would want to render the bike from the point of view of the camera, you would need to transform all of its vertices (in bike local space) to the space the camera sees them from (the camera local space, sometimes called view space). To do this, you would transform all your vertices like this:

Bike local space -> world space -> camera local space.

You need to pass through world space since you need to consider "where in the world" the bike is. The GPU actually requires you to transform the camera local space coordinates into what is called clip space. This usually happens in the vertex shader.

The different spaces have nothing to do with handedness. Usually you use either left-handed or right-handed coordinate systems, and thus all your different spaces would be left-handed or right handed. This is of course not enforced, but that's usually how it is.

### #1GuyWithBeard

Posted 19 January 2013 - 10:08 AM

Consider the following scene:<br /><br />- A parking lot area, the form of a square, with the world space origin in the middle of the parking lot area.<br />- A bike parked in the northeast corner of the parking lot.<br />- A camera which someone has left on a bench in the southwest corner of the parking lot.<br /><br />Both the camera and the bike have their own local spaces, and any position within their local space can be transformed into world space. First consider the bike. If you were to sit on it, the front of the bike would be facing "forward", and back "backward". You would grab the right part of the handlebar with your right hand, etc. All of these things remain the same regardless of where in the world the bike is. Whether it is upside down or lying on the ground. Its local space remains the same.<br /><br />To tell your game where in the world the bike is, its vertices have to be transformed, "moved to", world space. At this point it matters where the bike is and how it is orientated. If you move the bike from the north east corner to the northwest corner, the world position (and possibly orientation) of the bike seat changes. However, the local position of the seat is still the same (ie. it has not moved in regard to the other parts of the bike).<br /><br />Now consider the camera. It is not in the same place as the bike, so moving a position from its local space to world space is a different kind of transform, but the idea is the same.<br /><br />Now, if you would want to render the bike from the point of view of the camera, you would need to transform all of its vertices (in bike local space) to the space the camera sees them from (the camera local space, sometimes called view space). To do this, you would transform all your vertices like this:<br /><br />Bike local space -&gt; world space -&gt; camera local space.<br /><br />You need to pass through world space since you need to consider "where in the world" the bike is. The GPU actually requires you to transform the camera local space coordinates into what is called clip space. This usually happens in the vertex shader.<br /><br />The different spaces have nothing to do with handedness. Usually you use either left-handed or right-handed coordinate systems, and thus all your different spaces would be left-handed or right handed. This is of course not enforced, but that's usually how it is.

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