Invisible material that casts shadows

[ArchPrime]

Hi, has anyone figured out how to make certain elements in ArchiCAD invisible to the camera, but still cast shadows?

I want to do an ArchiCAD sun study using Octane engine, where from a camera view looking down on the whole building, the roof of the building is invisible so the daylight & shadows cast by walls and windows can be seen, without any daylight getting through the invisible roof.

I saw a reference elsewhere to an option in Octane standalone to make objects invisible to camera - but that does not seem to help in the plugin. I need to use the plugin rather than standalone, so that the ArchiCAD sun study tool can overlay time of day and date information on each frame.

As far as I can tell, the only ArchiCAD model attributes accessible to the plugin are surface materials?

[paride4331]

Hi ArchPrime,
I'm not an ArchiCAD skilled but you would check shadow catcher option in diffuse material that you will apply to catch the shadow.
Regards
Paride

[ArchPrime]

Hi ArchPrime,
I'm not an ArchiCAD skilled but you would check shadow catcher option in diffuse material that you will apply to catch the shadow.
Regards
Paride

Thanks Paride

I tried that, but applying material to roof, for me all that enabling the shadow catcher toggle does is make the applied roof material a solid grey (i.e no shadows are being cast upon the roof material). If I reduce opacity to 0, the roof disappears, but then lets the light through rather than casting the required shadow on the floor below.

Am I missing something? Shadow catcher seems to affect whether shadows are cast upon a material rather than by a material...?

[paride4331]

Hi Archprime,
you should activate "alpha chanel" in your kernel setting. This option removes the background and renders it as transparant (zero alpha).
This can be useful if the user wants to composite the render over another image and does not want the background to be present when shadow catcher is active.
Regards
Paride

[ArchPrime]

Hi Archprime,
you should activate "alpha chanel" in your kernel setting. This option removes the background and renders it as transparant (zero alpha).
This can be useful if the user wants to composite the render over another image and does not want the background to be present when shadow catcher is active.
Regards
Paride

THanks Paride

For me enabling alpha channel removes the scene background and makes the roof material black but opaque. If I set opacity to zero for material, it still cast no shadows on the floor below...
Is there something else I should be setting?

[paride4331]

Hi Archprime,
you have not set opacity to 0.
You can see how to in 3ds Max but sould be the same in Archicad.
viewtopic.php?f=27&t=60496&p=309529&hil ... er#p309529
Regards
Paride

[ArchPrime]

Hi Archprime,
you have not set opacity to 0.
You can see how to in 3ds Max but sould be the same in Archicad.
viewtopic.php?f=27&t=60496&p=309529&hil ... er#p309529
Regards
Paride

Hi, please see attached screenshots showing results with opacity=o vs. opacity=1
You can see that when opacity=o, the roof material cast no shadows, and when it is 1, the roof material is solid black
This is with Alpha Chanel set to enabled in kernel.

Opacity=1

Opacity=0