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Thread: COLLADA 1.5 Camera Orientation

  1. #1

    Question COLLADA 1.5 Camera Orientation

    Hi,

    I came here from: https://forums.khronos.org/showthrea...ra-orientation

    But COLLADA 1.5 says:
    The camera is defined such that the local +X axis is to the right, the lens looks towards the local -Z axis, and the top of the camera is aligned with the local +Y axis (also see the <lookat> element). This orientation is affected by the <asset> elementís <up_axis> value.

    I'm confused a bit, camera element has it's own asset element and there is a global <asset> too.
    Does camera element/orientation inherit the global (document) or any parent <asset><up_axis> if <camera> doesnt have one?

  2. #2
    Senior Member
    Join Date
    Mar 2016
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    106
    The orientation of nested assets overrides those of the parent. They are not in terms of the parent's parameters. This is covered first thing in <asset> section of the 1.5 PDF specification. That's the first place you should look for semantics.

  3. #3
    Thanks, now I see the statement:

    Details
    In the case of hierarchical <asset> elements, where both the parent and child assets supply a value for the same metadata, such as for <unit>, the child assetís value supersedes the parentís value within the scope of the child element. This applies recursively.


    But if camera always loking toward -Z (https://forums.khronos.org/showthrea...ra-orientation)
    then, Does <up_axis> meaningful for <camera>? There are lookat and other transform elements in <node> which are define camera orientation/rotation

  4. #4
    Senior Member
    Join Date
    Mar 2016
    Posts
    106
    I don't know. I don't have any real experience with the semantics. If there was good software that implements COLLADA you could see what they do. These things can get very complicated.

    The <up_axis> is mainly for numbers inside the element. So if <lookat> is inside the <camera> then it's in terms of the camera. It's for if you link to a document that uses different conventions.

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