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Messages - pokoy

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1
PNG, JPEG, EXR and TIF all use compression to some degree, plus, HDR formats use more bits per channel than LDR formats.
For rendering, image data will be uncompressed hence a higher RAM consumption.

2
Have loosely followed the thread, so sorry if it's been mentioned and tested already, but could out of core features have something to do with it? They're created only for Corona bitmaps so might be worth trying to disable that feature.

3
Maybe totally unrelated but I recently had a similar problem where exr files would throw an I/O error and not save.
Turns out it was an Umlaut in the path name and the solution was to remove any non-english characters in the path or filename.

4
Here are my tests:

1. Cylinder - original object -> seam visible


2. Cylinder - reconstructed in CAD -> no seam visible


3. Lens - original object -> heavy artifacts visible


4. Lens - reconstructed in CAD, imported as BodyObject, Face Angle 10 -> less artifacts visible


5. Lens - reconstructed in CAD, imported as BodyObject, Face Angle 1 -> no artifacts visible



The cylindric objects - mystery remains but it looks like a clean start resolves the issue.

As for the lens - yes, artifacts will be visible, probably due to the fact that Corona doesn't interpolate explicit normals (like it does for normal smoothing).

The only solution (or rather a workaround, not a solution) I found is to use high tessellation. If you import the original CAD file in an format that Max can read, you can dynamically change the tessellation to whatever is needed.
For this to work: Import file > Convert to Mesh = OFF, this will import the object as a BodyObject where tessellation can be controlled at any time.

Attaching a zip file with the max 2021 scene and the exported IGS CAD objects from MoI3d.

FWIW - @OP, you'll find similar problems with shading for non-transparent objects. Two options to handle this:
- again, high tessellation
- or: Render dialog > 'Development/Experimental Stuff' rollout (might have to be enabled in Corona System setting, enabled by checking 'enable devel/debug mode') > 'Terminator Handling' > set 'Shadow Shift' to 1 (0 by default). This will mostly fix shadowing artifacts on CAD models. Might however introduce shading artifacts on low resolution geometry using standard Max smoothing.

Guess development needs to have a look at properly handling CAD normals sooner or later. We have to use workarounds for quite some time now so please have some mercy devs :D

5
At least for the cylinder, there's a tiny angle at the center. In my CAD test object, there's no seam visible. You probably mirrored one half of the object but there's a tiny angle at the center, resulting in a slight break in surface continuity. Sorry if you feel like I'm stepping on your toe but the tessellation suggests this, too, and I just can't think of any other reason why a cylinder should have a slight angle at its center.
For the lens object - mine looks less mangled but it still displays some clearly visible artifacts at the edges.

In Corona, light/camera normals and surface normals are two different things, similar to how shadows will produce artifacts on the shadow terminator or SSS/absorption will reveal geometry tessellation. On top of that, Corona can't properly handle explicit normals in some cases. At least for the lens object, it's quite inacceptable.

Devs/support should chime in and give their perspective but this is a long standing issue and with the current target audience (archviz/DCC apps not CAD) I guess the priority will be low.

For the record, I totally support this and think that CAD objects should render perfectly in Corona, too.

FWIW, I'm rendering some comparisons and will post images + a max scene.

6
You're right, seeing this one now, too.

An explanation might be that the OBJ exporter does that, or the import does weird things.
Another reason might be that the objects aren't modeled accurately in the CAD app. The tessellation on both objects suggests that there are irregularities in the surfaces itself, these might be a result of manual placing of control points. Especially for the cylindric mesh, the tessellation should be completely regular at the center but it's not, suggesting there actually IS a sharp seam.

I'm currently reconstructing both objects in CAD to check if accurately modeled surfaces would introduce similar artifacts. On a quick cylinder test, I'm not seeing any problems at all.

@OP - if you can, please share both objects in CAD formats, either 3dm, STEP or IGES will do.

7
Oh wait, I'm seeing it now, missed the artifacts on the lens type of mesh. The cylindrical mesh looks good however. It's strange indeed.

@OP - can you post the CAD objects exported to IGES or STEP? Since you can import these in Max it's worth trying going with CAD formats imported directly instead.

8
I'm on max 2021.

Looking at your mesh screenshot, the wire looks identical in both cases (imported, not rebuilt), that's why I was asking.

9
Strange, what do you mean by rebuild? The mesh looks like it's the same...

I'm on Max2021 with Corona 9hf1 so can't open your file. It might be that it's why I'm seeing a different result but I doubt it.

10
The OBJ exports are fine and render perfectly for me, you are probably removing normals either on import or with an operation/modifier in Max.

There's a difference in how surface normals are created in CAD apps vs Max.
In CAD, the surface curvature is typically perfectly described by mathematical functions (yeah, super simplistic way to put it) and for mesh display/rendering, the surface is tesselated, with each triangle/polygon getting a surface normal derived from these functions which is very accurate and independent from mesh resolution. The result is that, even for coarse tessellation, the surface curvature looks good. This is called 'explicit normals' in Max and you should always try to keep them when importing CAD meshes into Max.

In Max, the concept of smoothing means that surface normals are calculated by averaging the face/polygon vertices which is heavily dependent on the tessellation and will be worse than what CAD apps are doing, especially with triangulated meshes (quad meshes are better suited for this).

It looks like you are not importing explicit normals correctly, or removing/invalidating them in Max. Various modifiers will invalidate explicit normals on imported CAD meshes, so will space warps, Booleans (or attaching/detaching mesh elements in earlier Max versions). Once invalidated, Max will fall back to using smoothing groups which will not look well on triangulated meshes, this is what's happening here.

On OBJ import make sure, that in the dialog's 'Normals' section 'Import from file' is enabled.
To check if a CAD imported object has correct normals in Max, use an 'Edit normals' modifier on the object - if it displays green normals, you've imported and kept them, and the object will render fine. If they're blue, it means you have either not imported them correctly, or some operation/modifier has removed them. Unfortunately, there's no way to get them back in Max without re-importing the object.

You may be facing a different issue with CAD meshes further down the road where the shadow terminator may look jagged (with non-transparent materials). This is due to the way Corona handles lighting vs surface normals. Let us know if you see this, there's a way to fix it but it may not be satisfactory. But it's unrelated to the issue you've been running into.

11
We understand that Corona is a physically-based renderer, but you allow little cheats here and there anyway. You also cant Exclude lights and include lights in a real world. I think all people are asking for is more control over the render! There is not photographer that does not photoshop the crap out of their images anyway, so I don't understand the argument about not letting people adjust stuff like this. To each their own I guess. But if it does not work that way under the hood that make sense.
In Corona, it's not possible to completely separate lighting and reflection and control each independently. Same for diffuse vs specular, they can't be separated 'cleanly', that's also why there are some limitations to or artifacts produced by overriding certain 'ray types'.
In Vray, these ray paths are separately calculated and it's possible to just disable them.
So it's not due to a decision by the team but the technique used by the renderer itself.

12
[Max] I need help! / Re: CPU usage drops to ~10%
« on: 2024-05-17, 10:57:34 »
Is fault tolerant heap still a thing? I have no idea if it can cause such an extreme usage drop but I remember it used to be a problem sometimes in the past.

13
[Max] I need help! / Re: Corona Sun doesn't work properly
« on: 2024-05-09, 15:41:44 »
What happens if you let only the sun enabled? Not in Ligthmix but for rendering, with only the sun light enabled? Maybe another light is absurdly strong and MSI is toning down every light in the scene?
Global Volume Mtl by any chance?

14
[Max] I need help! / Re: Corona Sun doesn't work properly
« on: 2024-05-09, 14:15:10 »
Isn't the Highlight Compression operator set to a bit too aggressive value? What happens when you set it to 1.0?

15
The weburbanist link is badly formatted (I had to remove the last few digits), facebook link works now.

In Corona, there's no way to rotate the focal plane against the sensor back,  that's why Tilt/Shift won't get you this effect. But it's perfectly achievable with exaggerated DOF settings, the info I've posted above should be enough to get you started.
If your scene scale is realistic - for example if you look at an area spanning kilometers - you will have to use unrealistically low values for the f-stop value, try going below 1.0, maybe even as low as <0.1 to make sure.
And don't forget to enable 'Depth of Field', otherwise you won't see any effect.

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