Stange Shadows in the water !

[pclavett]

Hi all ! Was doing another view from my Denali file and got strange shadows in the water ! The search could not find anything about this but did fine something about lines in the water, posted by Ulco (Dune).
https://planetside.co.uk/forums/index.php/topic,27379.msg271976.html#msg271976
Following the viewing of this thread I did a few experiments and did get rid of the artifact but it seems weirder than posted there ! The images are below. Test 3 was my first basic render to see the project and you can see that darker shadow in the water at the bottom. I then did a cropped render in Test 2 and it was gone. Another larger cropped render in Test 1 shows that the shadow is back but a bit different than Test 3 , having a straighter border on the right. After reading Dune's thread, did a render with GI cache detail reduced to 1 (default being 2) and got Test 4 with the shadow gone. I imagine that reducing the GI cache detail may affect quality of the render especially with objects so wanted to experiment progressive increase of the number. I did a Test 5 render cropped more vertically to see if the artifact was there (to decrease the render times of the experiment) with GI back at 2, and indeed it came back but much higher as compared to when done with the total image uncropped. Test 6 is done with GI cache back at 1, Test 7 at 1.3, Test 8 at 1.8, Test 9 at 1.9, Test 10 back at 2 where it comes back, although not exactly at the same level as Test 5 (which was the same settings, weird !) and going above 2 at 2.3 gives Test 11 where the shadow is not seen but the water is darker than before suggesting that the shadow was simply pushed up into the reflections and not as apparent ! So it seems that playing with the GI cache does permit the removal or at least make the artifact less apparent but want to see if anyone has had this problem and if other measures to fix it are available. So Dune's thread did permit a fix but wonder if things have changed since this was done 4 years ago. Appreciate your input and have a great day all !

[Kevin Kipper]

Hi pclavett,

I'm curious as to what the "Ray detail region" is set to under the renderer's Advanced Tab?  You might try setting it to "360 degree (optimal)" if it's not already.

Also, is the artifact really a shadow, say perhaps from an unseen cloud layer?  Or merely a reflection?

Here's the online doc's explaining the different settings for that parameter:
https://planetside.co.uk/wiki/index.php?title=Render_Node_(TG4)#Advanced_Tab

[pclavett]

No clouds on this project ! Nothing to reflect really ! I returned to the setup and rendered with the GI cache at 2 and again got thee shadow in Test 12. With the 360 degree detail (optimal option), I still had that shadow with the GI cache at 2, in Test13. So it still unclear to me what causes that shadowy area but Matt's view on the Dune 2019 post suggest that it has something to do with the GI prepass or some other factor relating to GI...... and just a tiny change from the default 2 to 1.9 makes it go away. Weird ! But then again, what do I know ! Thanks for the input !