Invisible Objects Visible in Render

[Mike Truly]

Vray 2.4.04

I have a scene of a house sitting on a terrain. I want the house to be invisible, but cast shadows on the terrain.

I have it setup such that the object properties of the house components are NOT visible to the camera, do NOT receive shadows but DO cast shadows,. In general, this is working fine... the invisible house casts shadows on the terrain.


Problem is... some parts of the windows are (faintly) showing in the render.



They are showing in the RGB and in the alpha. The windows are AEC windows and consist of a wood frame, metal and glass.

I have tried every setting I can think of but the windows still show in the render. The only thing that works is to make the windows NOT renderable... but then the windows don't cast shadows.

Any ideas? Are AEC windows trouble for Vray?

Thanks!

[Mike Truly]

OK, I got it sorted.

The Autodesk AEC windows are basically bad geometry (Thank You Autodesk!).

Even though the AEC windows render fine in the house beauty pass... when trying to make them 'Cast Shadows Only' for a different pass, the windows still show in the render because of bad geometric structure.

I replaced one of the AEC windows with one I built by hand and since the geometry is now clean... Vray renders it properly now. Sigh.

Thanks anyway!

[Mike Truly]

OK, although the geometry generated by Autodesk AEC Windows was total crap and building proper geometry fixed the particular problem mentioned above...


I'm having another problem which I think is related to the problem above. Namely, Vray 2.4 (back in the day) has a problem when looking at many stacked objects from certain camera views.


In this simple scenario, the camera swings around a group of deck board objects (perfectly clean geometry). The object properties and materials are set to be invisible to the camera and to cast shadows and to do nothing to the alpha channel.

As the camera begins it's move... the objects are invisible, cast shadows and don't affect alpha just perfectly as desired.

But when the camera gets to the mid point of its arc... the camera is looking edge-on at the group of objects and the objects become visible in the render! They also become visible in the alpha! This is not desired.

As the camera continues it's move to the end, the objects are no longer seen edge-on and the objects become invisible again both in the RGB and A... as desired.

See the attached images.


If I reduce the number of deck board objects that are shown (showing 7 board objects instead of 40+ objects)... when the camera is viewing the objects edge-on, the objects are properly invisible and don't affect alpha... as desired.


Back in the day with Vray 2.4... was there a setting somewhere to fix this broken behavior?

Did everyone just never view objects edge-on with their camera views?

When I brought this simple scene forward into Vray 5, the 'edge-on view' problem was gone so clearly code changes fixed this problem later.

Thanks for any ideas!

[hermit.crab]

Can't seem to reproduce the issue on a simple scene. Could you send the scene (or attach it here) via the contact form so we can take a look? Address it to me in the subject and include a link to this thread in the message.

[Mike Truly]

Thanks very much for taking a look at this!

vray_2_4_04_test_deck_boards_02.zip

As I mentioned, when I tried this scene in MAX2020/Vray 5.1 it renders perfectly... so it won't show you the problem in the latest version. If you can open it in an older version (Vray 3?), it might show you the problem. It definitely shows the problem in Vray 2.4.04.

Basically, if you render frame1 of the animation, it renders perfectly (objects invisible, casting shadows, no affect on alpha). If you render frame115 of the animation, the object becomes visible in the render and affects alpha (not desired). If you render a later frame (say frame300), it renders perfectly again. It is happening when the camera is viewing the objects edge-on.

More info: There are 46 deck boards. When all the boards are visible... the problem happens. If I only 24 boards are visible... the problem does not happen. If 25+ boards are visible... the problem starts to show itself.


In the real project render... this problem is happening with the deck boards as well as the roof panels. See attached image.


Thanks again.

[hermit.crab]

I see, I guess the issue was fixed along the way. Is there a reason for not rendering it in V-Ray 5?

[kosso_olli]

Raise the Max. Transparency levels considerably, like 100 or so. The problem will get better. It was a thing we often had to do back in the day.

[Mike Truly]

Thank you Oliver! Thank you Oliver! Thank you Oliver!!! That fixed the problem!!! I knew an old-time Vray user had seen this problem before.


There are many animations to render on this project. Currently, my rendering pipeline is built around the older version of Vray. The time and cost (and limitations) of rebuilding the pipeline to use Vray5 are too much at the moment. I am hoping to upgrade the net-render pipeline at some future time. For now, I use what I have.

Thanks again to all!

[kosso_olli]

Thank you Oliver! Thank you Oliver! Thank you Oliver!!! That fixed the problem!!! I knew an old-time Vray user had seen this problem before.

You're welcome!