changing the camera upvector lets visual objects disappear about vsgexamples

[robertosfield]

On Fri, 18 Mar 2022 at 10:20, Rainer Gericke ***@***.***> wrote: Hi Robert, for project::chrono we need an optional upvector (0,1,0) for backward compatibility to older model files. Changing the upvector in vsg programs let all visual objects vanish yet. vsgskybox is a good example for testing this. I guess it is not intended. Could you provide a modified example to illustrate the problem and the

settings you are using. Is it possible to share the problem data?

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Message ID: ***@***.***>

[rainergericke]

Yes here is it. It is just the standard vsgskybox example. With upvector (0,0,1) it works, building with upvector (0,1,0) it shows nothing but the background.

Both versions have been started with (on MacOS 12.3)

upvector models/teapot.vsgt --skybox textures/skybox.dds

Upvector.zip

[rainergericke]

Oh, maybe I know, what happend. The line of sight is parallel to y, when y is used as an upvector, a singularity occurs.

[rainergericke]

I am going to implement a test for colinearity between line of sight and upvector in my software, that should do it.

[robertosfield]

Good to hear you've found a way to resolve the issue. It might be that the vsg::LookAt code needs a review to see if can do a better job at handling the look vector and up vector being aligned. I presume this is the root of the problem from your description. There is only so much one can do though with invalid combinations of inputs. Message ID: ***@***.*** com>

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