0

I have been trying to render my doughnut. However, I have been experiencing difficulties when I use Cycles. The doughnut would have blurry black spots whenever I was using Cycles to render. This doesn't happen when using Eevee. The render settings and also the screenshot using render viewport is provided (same effect with render viewport or normal renders)

enter image description here enter image description here enter image description here

ManaTree
  • 84
  • 1
  • 10
Outsidermm
  • 31
  • 5
  • Hi, could you provide a screenshot of your icing's material please? – L0Lock Jul 26 '23 at 23:47
  • Hello, the icing material is within the post after I re-edited it. Thank you! – Outsidermm Jul 27 '23 at 00:33
  • 1
    Does the icing intersect with the doughnut mesh? Cycles uses volumetric subsurface scattering, so weird things can happen when there is a surface inside of the scattering volume. This is a common problem with skin, such as where lips touch and joints bend inward. You can check if this is the issue by hiding the doughnut mesh. If it's still happening, check if the icing intersects with itself. – SupaKoopaTroopa64 Jul 27 '23 at 01:54
  • 1
    Could you please share your file? https://blend-exchange.com/ – moonboots Jul 27 '23 at 09:49
  • @SupaKoopaTroopa64 I hided the doughnut mesh and rendered with only the icing. The problem still exists. How do I check the icing intersects with itself? – Outsidermm Jul 27 '23 at 10:25
  • @moonboots I don't think that's possible, as the files are too big to send through. There is an entire scene with other objects included within the project. However, no other objects during rendering have this problem. – Outsidermm Jul 27 '23 at 10:25
  • only keep the donut and its icing and share? – moonboots Jul 27 '23 at 12:48
  • 1
    Maybe not the cause of the issue, but that's definitely too high of a subsurface value, usually we use values around 0.01. See materials - How to use Subsurface Scattering in Principled BSDF - Blender Stack Exchange. If you want translucency (which isn't really common in icings i think), adding a Translucent BSDF to your shader would be more appropriate. – L0Lock Jul 27 '23 at 14:39
  • Thank you all; by disabling the subsurface value, I was able to make the donut render as I intended. Thanks for all your help and contribution – Outsidermm Jul 27 '23 at 23:59
  • @Outsidermm I don't really know if there is an easy way to tell if a mesh intersects with itself besides looking very closely. Another thing that might be the problem is that your scattering depth is higher that the thickness of your mesh. I don't know how thick the icing is, but assuming the doughnut is the size of the default torus, I'd guess the icing is 30-50mm thick. Dividing your scattering amount by about 5 might do the trick. – SupaKoopaTroopa64 Jul 28 '23 at 01:35

2 Answers2

1

Thank you for all your input! I was able to resolve this issue by turning down the subsurface value.

Outsidermm
  • 31
  • 5
0

Check your topology. Black spots usually mean bad topology. If not that, then mess around with the subsurf value. EDIT Ok, I know one other solution. Turn up your transparency bounces until the black portion goes away. Maybe you can send a picture of your donut in edit mode as well?

For the transparency bounces, go to RenderProperties > LightBounces

Fanimation
  • 11
  • 1
  • What does topology specifically mean? I am a beginner, so I don't really know. Thank you for your help! – Outsidermm Jul 27 '23 at 01:27
  • Hello, Fanimation, this really needs fleshing out to be considered a truly helpful answer, IMO. For completion, I think you'd need to illustrate how bad topology can look like this. (Incidentally, this effect looks more like an anomaly arising from Subsurface Scattering settings .. but of course, I could be wrong) – Robin Betts Jul 27 '23 at 05:59
  • Yes, thats right @RobinBetts – Outsidermm Jul 27 '23 at 23:59
  • Topology is generally how cleanly or uniform the object has been modelled with consideration of vertex and edge spacing in relation to each other on a per model basis and clean edge loops in models which are going to animate or deform. The comment does need more clarification but I suspect they're referring to making sure there are no open faces, duplicate vertices/edges/faces which can cause a similar rendering effect. I've found Blender does this a lot when you're chopping and changing your models, especially when doing boolean operations and merge vertices operations sometimes don't work. – Helpme Jul 28 '23 at 16:01