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asam-ev / OpenMATERIAL

3D model exchange format with physical material properties for virtual development, test and validation of automated driving.
https://asam-ev.github.io/OpenMATERIAL/
Mozilla Public License 2.0
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EMP-Schema: Properties #122

Open lyndyRott opened 4 hours ago

lyndyRott commented 4 hours ago

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Problem: Fields for Reflectivity, IoR, transmission,... not found

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Within the emp-schema of the material properties, where do the reflection/transmission, index of refraction propterties are meant to be included? see: "electromagneticProperties" https://github.com/asam-ev/OpenMATERIAL/blob/main/schemas/material_emp_schema.json

ClemensLinnhoff commented 3 hours ago

The index of refraction can be calculated out of permeability and permittivity. Therefore we decided to not add ior explicitly to avoid redundancy in the data. But we should add this to the description so it is clear, along with the equation to calculate it.

What do you mean by reflection/transmission properties?

lyndyRott commented 3 hours ago

For some materials the permeability/permittivity might not be known (in particular some composites), but the reflection-transmission-absorption model is, or can be measured (more easily than the permeability/permittivity).

ClemensLinnhoff commented 2 hours ago

But reflection-transmission-absorption is highly angle dependent. This can then be put into a brdf lookup table.

lyndyRott commented 2 hours ago

I thought that BRFD only covers the reflection part of the material description.

lyndyRott commented 1 hour ago

Maybe we can include Lionel in this discussion on BRDF, BTDF and BSDF? https://optics.ansys.com/hc/en-us/articles/360042213854-Bidirectional-scattering-distribution-function-BSDF @lbennes-ansys

lbennes-ansys commented 8 minutes ago

I agree brdf only cover the reflection/absorbtion. but considering also the btdf is sually only considered in very advanced simulations. To be honest, for optical sensor simulations for automotive, we do not really see the transmission as having a lot of impact on the final result.

btdf can be added as optional maybe.

bsdf is way more complex to manage (spacially varying brdf). On our side, tackling real time simulation, we are using diffuse textures and normal variations to create spacial variability in our surface optical properties. I guess we could derive that from a btdf, but it implies a complex processing.

I would suggest to go for brdf + optional (btdf)