[x3d-public] glTF X3D comparison

[Andreas Plesch]

Transformation matrix, units ?

glTF uses meters and radians. There is no way to declare another unit as
scene unit.

Are there any specific glTF constructs that do not map to X3D capabilities
(for example skin)?

These can be mapped but are awkward:

Transforms can be directly given as matrix. Needs decomposition.

Binary buffer concept. Needs conversion.

Extension concept. Needs encapsulation in components.


Is current X3D lighting model incompatible or a subset of advanced features?

>From I could gather following glTF is that the BlinnPhong X3D shading model
is not really compatible with PBR. Both require different shaders and a
scene which uses both is considered to look awkward. One shading model
cannot be considered a subset of the other but people came with formulas to
approximate BlinnPhong with PBR.
Technically, it may not be necessary to introduce a special PBR light node
since the fields translate except perhaps attenuation which seems to work a
bit differently.


Andreas
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