[x3d-public] ideal points in IndexedFaceSet

[Andreas Plesch]

Another option to consider is the infinite perspective projection:

https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#infinite-perspective-projection

AFAIK it favors precision at large distances at the expense of precision at
zNear distances. Here is a discussion:

https://github.com/mrdoob/three.js/issues/11755

Infinite perspective could become a boolean field for Viewpoint:
infinite='true'

-Andreas



> Message: 2
> Date: Fri, 16 Feb 2018 13:13:05 -0800
> From: Andrey Filippov <andrey at elphel.com>
> To: GPU Group <gpugroup at gmail.com>
> Cc: "X3D Graphics public mailing list" <x3d-public at web3d.org>
> Subject: Re: [x3d-public] ideal points in IndexedFaceSet
> Message-ID: <161a076a591.d7ceb8a145606.5200096282464602015 at elphel.com>
> Content-Type: text/plain; charset="utf-8"
>
> Doug,
>
> Yes, I meant w=0. I thought that switching to MFVec4f would be too big of
> a change, and the only value of interest may cause div by zero. This is why
> I thought about a boolean finite/ideal. In my everyday job I'm rather far
> from CG, so maybe it is not easy to implement with existing shaders. Or
> maybe there are other equivalent solutions to handle faces with points at
> infinity. But at the first glance it could be a more elegant way than the
> Background node.
>
> In our particular application I needed non-uniform grid at infinity. We
> use frequency-domain processing for image aberration correction and stereo
> matching, and it is only shift-invariant, not scale-invariant. So using
> that we are camera manufacturers we pre-select lenses to have the same
> focal length (to ~1%), then individual lenses/sensors are mechanically
> adjusted to have the same optical axes and roll. Then we find common radial
> distortion approximation common for all 4 images, and only correct (in
> frequency domain) residual distortion. As a result the generated textures
> have (known) radial distortion that I take into account by correcting the
> 3d coordinates when generating x3d models IndexedFaceSet. For Background
> node I would need to apply full rectification to the image. When using
> 10,000 m flat "wall" I make it as a non-uniform grid, the same would be
> true if the fancy IndexedFaceSet was available.
>
> Andrey
>
>
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