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Topics - pokoy

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This one popped up some years ago during an online discussion and I had some funky results myself. Recently, I was using a dome-mapped environment with a ground plane with a ShadowCatcherMtl and realized that a reflective surface was reflecting something that was *behind* it which was clearly wrong. I decided to find out why that happened, turns out there's a bug when an environment is using dome mapping and is then used on a geometry with ShadowCatcherMtl.

In order to have a ground truth reference to test against I modeled simple test case scene - 4 different textures for the ground with 4 lights with some reflective objects. I then rendered a spherical panorama of that scene (with the reflective objects disabled for the pano). The Camera's Z-pos is at 5 meters.

Here's what the reference renderings looks like, one with spheres for lighting and reflections, another one with a box for flat reflections.

2 - VALIDATION - using the rendered pano as an environment in Dome mode
This is the scene using the reference panorama rendered before. It's set to dome mapping, 'Camera Height' is set to 5 meters to match the camera's height used to render the pano.
So far this looks good - except for the blurry environment, which is due to the low resolution of the environment map, so it's expected. Other than that, it matches the 'ground truth' reference renders from step 1.

This however is missing shadows since we don't have a ground plane. So let's add that...

3 - VALIDATION - add a ground plane with ShadowCatcherMtl (this is where the BUG is)
Now let's introduce a ground plane with a ShadowCatcherMtl using the environment map in its 'Enviro/Backplate' Slot and 'Projection mode' set to 'Enviro projection' (the correct way).

Have a look at the images, you can clearly see that reflections and GI are way off.
Notice the strange GI on the white sphere and the wrong reflections on the metal sphere.
Notice how the reflections on the metallic box are wrong. We should never see the red area of the ground being reflected since it's *behind* the box, and why is the reflected environment mirrored in a strange place? Nothing here makes sense.

This is clearly a bug. We're all using dome mapping with a ShadowCatcherMtl on some geometry in order to get shadows. Dome mapping alone works fine, but as soon as a ShadowCatcherMtl is used (and uses the same environment) it's doing something unexpected.

Luckily there's a simple workaround but it may not be applicable in all cases.
Instead of using the environment's dome mapping mode in the ShadowCatcherMtl, we can reproject the panorama on the ground plane, and this reprojected panorama will then be used.
To do this, use a UVW Mapping modifier on your groundplane, set it to spherical (since our environment is a spherical pano), set the modifier gizmo to Z=5 meters (or the height that your panorama was taken at) and rotate if needed to align with your background/reference. In the ShadowCatcherMtl, set 'Projection Mode' to 'Do not alter projection' - that way, we're using the UVs from the UVW modifier, not the environment map's mapping.

However, for this to work, the ground plane (or whatever you want to use as ground geometry) needs high tessellation, otherwise UVs will stretch quite a bit. In this case, the ground plane needs 80 segments in length and width.

Here are the images, GI and reflections are now correct.

@Corona Team - this is a long standing bug and it's amazing to me this was never reported or validated/caught internally. I'd really expect this to work, hopefully it'll be fixed soon.
I'm attaching the zipped scene+environment map. Scene is from Max 2021 with Corona 9HF1 but I'm pretty sure the bug is present in recent Corona versions.

[Max] Feature Requests / No motion blur with Distance Maps
« on: 2021-10-01, 10:49:46 »
I hit a roadblock due to this limitation yesterday - distance maps will not work with transform motion blur (camera motion blue works fine) - and in my case the workaround is a really painful one - instead of just using the Distance Map I need to bake color maps for 100 objects.
Hopefully, this limitation can be lifted since using distance maps solves a lot of work in some cases.

Attaching an image showing the problem and a scene - max 2021, Corona 7.

[Max] Feature Requests / CIE - a few requests
« on: 2020-10-15, 21:03:51 »
I couldn't find the original CIE request thread, it's been probably moved, so here are a few things I have already requested in the past hoping they could make it in at some point.

1. Better post denoising options
- With 'Gather data for later ' we can include the data needed for either AI or Corona denoisers. If possible, please add an options to include all options (AI and Corona), so we can decide which one is best later in post.
- Sometimes a denoiser set to 0.5 is all I need - but I still may have some fireflies. Right now, I can only either denoiser OR remove fireflies. Please make fireflies removal an extra option, so it can be accessed and used in addition to the denoiser.

2. TIF + Alpha should keep pixels outside of alpha
Currently, including alpha in a TIF will remove all pixel information outside of alpha. It forces us to save two files, one without alpha and another with alpha, if you want to use the TIF and alpha in PS for example. Please improve this by making sure TIFs with alpha have all pixels preserved.

3. Include Scene Stats in CXR
I would really love to be able to see the render time, camera name, cache type, noise level etc. All this info is not kept in the CXR but it would be sometimes very useful to have this data stored along with it. I know we can currently include the Render Stamp but it needs some manual setup for some of the info first. Would be much better if it was saved with the file.

Thank you guys, as always - you rock!

I'm using the Mesher Compound object on a particle system SuperSpray object. The Mesher Compound useful when you want to use geometry based modifiers or a Corona displacement modifier on a particle system since you can't do this directly on any particle object.
Rendering works fine until geometry motion blur is enabled - in this case, Corona will hang while parsing the scene and eventually crash to desktop. Unfortunately no minidump is created.

I tested Mesher with standard animated geometry and it works fine. It looks like it's happening on particle systems only.
Is there anything that can be done about it?

Attaching a scene - Max 2020, Corona v5

To repro:
- open the scene, the layer '01_Mesher_Standard_Geometry' is visible
- render
>>> all works, motion blur works on the sphere with animated noise and the mesher object

- unhide the layer '02_Mesher_Particle_Object'
- render
>>> Corona will hang/freeze and eventually crash to desktop.

Note that if you disable motion blur in the camera it works fine.
The offending object is colored red in the viewport ;)

Additional note - it looks like the particle spray is causing problems and leads to crashes even if no mesher object is visible. If you make the motion blur to last longer - 1s for example - Max will eventually crash when scrubbing the timeline and forcing it to update while in IR. This time it crashes with the CER dialog. Attaching the minidump from that crash, too.

Max 2020, Corona v5

Open the attached scene, open Slate.

In the viewport you'll see a plane with an OSL noise displayed.
In Slate you'll see a map tree that is fed into the diffuse channel of a Standard Material and a Corona Material.

The plane has the Standard Material assigned, make sure viewport is set to HQ mode to display OSL correctly. Now assign the Corona Material to the plane and it will display a wrong result. It will only match the Standard Map when rendered, but we need it to display correctly in the viewport.

If you now remove the OSL noise map named 'UVW modulator' from the OSL UVW Channel map it will match the result of the Standard Material. For some reason, Corona Mtl can't display OSL correctly in the viewports if UVWs are modulated.q

Using Max 2020.2 and Corona v4 HF1 - CoronaCam with motion blur triggers IR to redraw as soon as the mouse pointer hovers over the viewport.
Didn't test with earlier Max versions, so not sure if it happens only in Max 2020.

Max + Corona v4 HF1

I stumbled across this recently (again) and saw that I've already reported this for Corona v3 HF1 and it's still present in v4... please resolve this, the problem seems to persist although I remember it being solved at some point in v2.

Repro steps:
Open the attached file, make sure both HDR files are linked correctly in Max.
- open the classic mat ed, you'll see the two environment maps in the top slots
- use either of the environment maps in the Environment override slot
- switch the used map to dome mode, render >>> block artifacts
- switch the used map to spherical map, render >>> all good

Make sure to use both maps to see how bad it can get :-/

Scene (Max 2018), textures and the resulting renders are attached.

So this one is surprising and caused a hang once, now crashed.
I am doing a fluid sim, the fluid sim dialog is open, and the fluid emitter selected, auto key is enabled.
I accidentally hit the 'm' button, and the material editor (classic) opens up and max crashes.

Max 2019, Corona 4 - minidump attached.

I have no scene for this as it sometimes works correctly, sometimes fails. Please follow these steps to reproduce:

1. create a few objects
2. Use some of these objects in a Corona Distance Map in a Material
3. Copy/Paste (not instance!) this Distance Map to another Material
4. Try to change the object assignment in the copied Distance Map (not the original)

>>> For me, the objects in the list will often 'stick', or objects will only be removed/added when I exit the Distance Map and display again. Sometimes, objects in a copied Distance Map cannot be removed at all and require you to create a new Distance Map from scratch instead of just copying it.

I hoped this one would be fixed for good but it seems it gets a comeback.

The dome light mode produces nasty block artifacts, see attached image.

Also attached is a zip file of a Max 2018/Corona v3_HF1 scene as repro case, and an image of the render results.
2 different environment maps are included and prepared in the material editor, please make sure to test both.

Please make sure to add this or a similar scene setup to your test scene suite. It's worth noting that the issue will NOT come up when there's a geometry under the objects (for example a groundplane) large enough to obstruct the parts of the dome map that produce the errors. Probably a reason why it hasn't been caught before release.

Max/Corona v3

It seems that the CoronaCam reparses scene with IR when changing the Shutter Speed when motion blur is disabled, however, reparsing should only occur with motion blur enabled. To verify that it's not something else, changing ISO/f-Stop doesn't seem to trigger reparsing and changes are visible immediately.

This is probably not visible on simple scenes where parsing is fast, please test on heavier scenes to confirm.

[Max] Resolved Bugs / 3ds max - AI Denoiser failed
« on: 2018-12-06, 21:58:31 »
So Max (2018) had a viewport error where it wouldn't update the viewports, but managed to recover after a files save. However, when rendering with the AI denoiser enabled, this error prompt came up:
Internal error in NVIDIA AI Denoiser. Please report this to Corona support with this info:

Error encountered during denoising.
Unknown error (Details: Function "_rtCommandListExecute" caught exception: Failed to launch DLDenoiser post-processing stage. DLDenoiser run method failed with error -27.)

I guess it's not safe to use Max after a viewport error (probably a driver crash), reporting in case it can be resolved on your end.

So this is something that dates way back to the first stable releases. It was mentioned a few times and reported afaik but it seems to be still there. Output shown here is from Corona 3 RC4.

If you enable sharpen/blur in Corona's VFB in Max, the output (saved to 16bit TIF here) will show serious artifacts. However, the same output, saved to CXR from Max, opened in CIE and saved to TIF will how no artifacts. See attached images and scene file (images were made brighter in PS to display the problem, max file is 2018).

Can we make sure this is fixed for v3? Basically, it means that all output from Max VFB to anything else than CXR (or TIF in any case, didn't test other formats) will show this artifacts when using sharpen/blur.

So this is a rather artistic setup:
- Object A uses displacement, where displacement is driven by a Object B fed into a Distance Map

Crash when moving Object B while IR is running.

I have often noticed that moving or manipulating objects used in a Distance Map while IR is running take either very long time to update or cause Max to get unstable, unresponsive, or simply crash to desktop.

Minidump attached.
Thank you!

Specs - Max 2016, Corona v2

Everytime I have to set up masks for RE I wish we had easier selection methods - IDs are good but hard to visualize and to find once you've set them up, selections sets are a pain with bigger scenes since it takes quite a lot of time to open, browse and select from a object list with 10 000 or more items.

I'd like to request the following selection methods:

• Layer - a drop down list of current scene layers (which updates dynamically when new layers are added or changed). All objects on a selected layer would be rendered in the mask
• Name string - a string field that accepts wildcards and multiple strings (separated by semicolons for example, like this: tree*;*car*tire*), all objects where the name begins with 'tree' and all objects where the name contains 'car*tire' would be rendered in the mask. Strings could also be separated by a comma or brackets...

Once these methods are available, they could also be added to any other place where Corona uses Include/Exclude lists - CoronaCam, RoundedEdgesMap, CScatter objects etc...
Attached is a mockup for the Mask RE (the methods should be available in any channel of course).

I know it would make it a lot easier to setup masks for me and I bet for many others, too.

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