Where is this shadow coming from?
Posted: 23 February 2021 12:54 PM   [ Ignore ]  
Avatar
Total Posts:  34
Joined  2019-09-30

I’ve got a medical image layout out and have added a light to highlight the area where a needle makes an injection.

I’m getting a weird circular shadow and I can’t for the life of me figure out what’s casting it.

Anyone? Thanks.

Image Attachments
Round Shadow.pngGouraud Shade Display.png
Profile
 
 
Posted: 23 February 2021 01:31 PM   [ Ignore ]   [ # 1 ]  
Moderator
Avatar
Total Posts:  9454
Joined  2011-03-03

Hi rcates,

From images, I can’t tell. If I can get the scene file, I will explore it.

What you can do, perhaps create a Multi-pass with a pass for each light.

Check the options of the editor.

Anything else would be a long guessing session, which I always find very unprofessional, as I believe it will take too much of the time of the one with the problem.

Do you need an upload link? (If you have Dropbox, Amazon, Adobe, Apple, Google, or Wetransfer, I will use it, other cloud services will be ignored for security reasons.

Cheers

 Signature 

Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004

Photography For C4D Artists: 200 Free Tutorials. Texture, Panorama, HDRI, Camera Projection, etc.
https://www.youtube.com/user/DrSassiLA/playlists

Profile
 
 
Posted: 23 February 2021 02:08 PM   [ Ignore ]   [ # 2 ]  
Avatar
Total Posts:  34
Joined  2019-09-30

Thank you for the response Dr. Sassi,

As is always the case, walking away and mulling over it made me think. If I turn off that light and create a new one I may be able to find the solution by rendering a test, make a change, render a test.

It appears the light falloff and light position play a part. The shadow changes as I make adjustments to those. If I still can’t nail it down I’ll send the file less the textures - big file.

Thanks,
R.Cates

Profile
 
 
Posted: 23 February 2021 02:15 PM   [ Ignore ]   [ # 3 ]  
Moderator
Avatar
Total Posts:  9454
Joined  2011-03-03

Thanks for the update, R.Cates.

I have sent you an upload link, just in case.

All the best

 Signature 

Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004

Photography For C4D Artists: 200 Free Tutorials. Texture, Panorama, HDRI, Camera Projection, etc.
https://www.youtube.com/user/DrSassiLA/playlists

Profile
 
 
Posted: 23 February 2021 03:33 PM   [ Ignore ]   [ # 4 ]  
Moderator
Avatar
Total Posts:  9454
Joined  2011-03-03

Thanks for the file, rcates!

This clears it. You used a “soft shadow”. With that, you are in shadow fake land.

This option produces no real shadow. It probes the space, and if the light is at a certain point behind the object’s surface, it will mix this with other probes, and it is either light or dark. This light source is fast based on the fake. I would avoid it if possible.

So, how to use it anyway? Set the Attribute Manager> Shadow> Bias (Abs) to a very low value, 0.1 for example (more probe-points), then the “shadow” will move behind the surface. Or uncheck Absolute Bias and leave it (here) at 1%.

The shadow map was also very low, especially for a point light.

Cheers

 Signature 

Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004

Photography For C4D Artists: 200 Free Tutorials. Texture, Panorama, HDRI, Camera Projection, etc.
https://www.youtube.com/user/DrSassiLA/playlists

Profile
 
 
Posted: 23 February 2021 04:08 PM   [ Ignore ]   [ # 5 ]  
Avatar
Total Posts:  34
Joined  2019-09-30

Outstanding, Thanks you sooo Much. Was hoping to set this up to render this evening. I’m confident I can now.

I appreciate your experience and willingness to help.

R.Cates

Profile
 
 
Posted: 23 February 2021 04:13 PM   [ Ignore ]   [ # 6 ]  
Moderator
Avatar
Total Posts:  9454
Joined  2011-03-03

Thanks for the kind feedback, R. Cates!

Yes, the first probe points were already inside the object; hence the shadow

If there is some flickering in the shadows, you will know what to change.

My best wishes for your production!

 Signature 

Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004

Photography For C4D Artists: 200 Free Tutorials. Texture, Panorama, HDRI, Camera Projection, etc.
https://www.youtube.com/user/DrSassiLA/playlists

Profile