Facet artefact when render imported obj mesh

[Oxide]

Hi, Everyone, new to luxcore here.

Luxcore is a very great render, especially for caustics and dispersion, as a jewelry designer I would like to use luxcore to visualise my works. My work flow basically is modelling in Rhino and exporting model to other program to render like keyshot or blender.

Recently, I met a facet render artefact when I tried to render model imported from rhino into blender. Image below is rendered by luxcore all default settings.


The model is highly smoothed mesh, and didn`t show facet artefact when rendered by eevee, cycles and octane(all default settings in these three renders as well with the same HDRI).

rendered by eevee


rendered by cycles


rendered by Octane


Not sure if it`s a bug or caused by my wrong settings, I would like to ask for some help.

Many thanks

[Dade]

What is the scale/size of the object in Blender ? Do you get the same problem both with CPU-only and GPU-only rendering ?

I have also some vague memory of problems with normals of imported objects from external CADs, some people here may be able to add some more details.

Are you using LuxCoreRender v2.3 or under development v2.4 ?

[Oxide]

What is the scale/size of the object in Blender ? Do you get the same problem both with CPU-only and GPU-only rendering ?

I have also some vague memory of problems with normals of imported objects from external CADs, some people here may be able to add some more details.

Are you using LuxCoreRender v2.3 or under development v2.4 ?

Hi Dade,

thanks for replying so soon.

I`m using Luxcore 2.3.

Object diameter is around 18mm orinally in Rhino, but it became 18m after imported into blender, all scale keep default and render shows artefact.

I`ve tried to set unit scale to 0.001 to make 1 unit equals to 1mm or set object scale to 0.001 and keep unit scale to 1, but the artefact keeps still under both condition, And keeps appearing under both CPU and Opencl mode as well.

And also I followed advises from luxcore wiki to set min epsilon larger (tried 0.00001, 0.0001, 0.001, 0.01 and 0.1) but it`s not working as well.

For more information:

Blender version - 2.82a
Operation system - win 8.1 64bit
CPU - i7 2.5GH
GPU - Geforce 860M

[Dade]

I`m using Luxcore 2.3.

Object diameter is around 18mm orinally in Rhino, but it became 18m after imported into blender, all scale keep default and render shows artefact.

You should try to use v2.4, as far as I remember v2.3 didn't had the support for Blender split normal, or something like that, and they were pretty common in models imported from external sources.

Can you also post a test scene showing the problem ?

[Oxide]

I`m using Luxcore 2.3.

Object diameter is around 18mm orinally in Rhino, but it became 18m after imported into blender, all scale keep default and render shows artefact.

You should try to use v2.4, as far as I remember v2.3 didn't had the support for Blender split normal, or something like that, and they were pretty common in models imported from external sources.

Can you also post a test scene showing the problem ?

Thank you for your advise, I`ll try 2.4 to see how it works. The attachment is my scene file, it is a bespoke piece so I have to modify it a bit, but I kept the main part of ring to demonstrate the artefact.

[kintuX]

Basically, you have double vertices, split faces in your geometry with "Custom Split Normal data", that's why shading visually breaks...

To fix, go into edit mode and Merge By Distance with "Unselected" checked (ex "Remove doubles")
after, "Clear Custom Normals"
et voila.


BTW
And yes, to have predictable, correct lighting you'll still need to set proper Unit scale (0.001).


Have a great day and experience with LuxCore.

[Oxide]

Basically, you have double vertices, split faces in your geometry with "Custom Split Normal data", that's why shading visually breaks...

To fix, go into edit mode and Merge By Distance with "Unselected" checked (ex "Remove doubles")
after, "Clear Custom Normals"
et voila.


BTW
And yes, to have predictable, correct lighting you'll still need to set proper Unit scale (0.001).


Have a great day and experience with LuxCore.

Thanks Kintux, I`ll put this on my note, It·s solved.