SSS shader behaves differently when all the meshes are merged into one object, or separated #56914

New Issue

Denise · 2018-09-25T12:06:30+02:00

Denise commented

2018-09-25 12:06:30 +02:00

Windows 7, Nvidia GeForce GTX 750 Ti
Blender 2.79b f4dc9f9d68, and 2.79, 2.8

Problem:
By applying a Subsurface Scattering shader on a not big object made of multiple meshes, it creates unnatural glowing areas where the meshes collide or are too close each other. This doesn't happen if all the meshes are separated into different objects, rendering it in a more natural way. It's quite desiderable to have it working also as an unique merged object, in cases like cooked spaghetti (or pasta in general) that have a lot of meshes and to have all of them separated is totally unhandy.
Before writing here I have tested a model of spaghetti, merged into an unique object, in Cinema4D (V-Ray) with its SSS (and it works normally as expected without glowing areas).

To reproduce it:
Create a bunch of simple cubes intersecting each other or very close each other;
Make them little like cubes of cheese, about 1cm each in a metric system;
Duplicate them, and merge the second group into a single object;
Apply a simple SSS shader, using the node or the Principled shader; Apply a color and set Scale and Radius all to 1;
Add lights or and HDRI image;
Start a render to see the difference.

Windows 7, Nvidia GeForce GTX 750 Ti Blender 2.79b f4dc9f9d68b, and 2.79, 2.8 **Problem:** By applying a Subsurface Scattering shader on a not big object made of multiple meshes, it creates unnatural glowing areas where the meshes collide or are too close each other. This doesn't happen if all the meshes are separated into different objects, rendering it in a more natural way. It's quite desiderable to have it working also as an unique merged object, in cases like cooked spaghetti (or pasta in general) that have a lot of meshes and to have all of them separated is totally unhandy. Before writing here I have tested a model of spaghetti, merged into an unique object, in Cinema4D (V-Ray) with its SSS (and it works normally as expected without glowing areas). **To reproduce it:** Create a bunch of simple cubes intersecting each other or very close each other; Make them little like cubes of cheese, about 1cm each in a metric system; Duplicate them, and merge the second group into a single object; Apply a simple SSS shader, using the node or the Principled shader; Apply a color and set Scale and Radius all to 1; Add lights or and HDRI image; Start a render to see the difference.

Denise commented

2018-09-25 12:06:30 +02:00

Added subscriber: @mysis

Jacques Lucke commented

2018-09-25 12:14:06 +02:00

Added subscriber: @JacquesLucke

Jacques Lucke commented

2018-09-25 12:14:06 +02:00

I don't if this is a bug or a limitation. But in any case it would be good if you could prepare a simple example file to reproduce the behavior. That would save as some time.
Thank you.

I don't if this is a bug or a limitation. But in any case it would be good if you could prepare a simple example file to reproduce the behavior. That would save as some time. Thank you.

Brecht Van Lommel commented

2018-09-25 18:06:52 +02:00

Added subscriber: @brecht

Brecht Van Lommel commented

2018-09-25 18:06:52 +02:00

Changed status from 'Open' to: 'Archived'

Brecht Van Lommel closed this issue

2018-09-25 18:06:52 +02:00

Brecht Van Lommel self-assigned this 2018-09-25 18:06:52 +02:00

Brecht Van Lommel commented

2018-09-25 18:06:52 +02:00

It's a know limitation currently. Some other renderers have a way to specify which groups of objects should be considered as one, but that's a feature request, not something we handle as a bug.

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SSS shader behaves differently when all the meshes are merged into one object, or separated #56914