Shadow artifact at corners of meshes

I see these shadow artifacts appearing at the corners of meshes. I see it in all versions and in all rendering pipelines (the effect is more pronounced in the LRP).

What is this and how can I get rid of it?

 

Shadow acne

 

Thanks for letting me know. Seems like a real bullshit problem - it doesnt seem easy to remove completely. I tried changing the bias in the lighting settings but that brought on other problems. It seems best to adjust the angle of the directional lights so that the effect are not seen by the player.

 

Yep. It's a problem AAA games struggle with. It's usually solved by careful planning of light direction and geometry, but you can find it in the latest games if you look for it. Most games will err on the side of overly blurred shadows with "peter panning", which is what it's called when you have a very high bias to push the start of the shadow away from the casting surface, which can sometimes cause objects' shadows to not connect to the place they touch the ground. To hide that several modern games make use of AO or screen space shadows, and now raytracing, to cover the gap.

This example from Nvidia's official post on Control's use of Raytracing is a good example.
https://images.nvidia.com/geforce-c...e-comparison-001-all-rt-on-vs-all-rt-off.html
On the left side the chair legs cast nice sharp shadows on the floor, grounding them in the scene. On the right the shadows fade in over some distance so the legs appear floating. Other places like the jacket or the fingers on her hand are casting shadows where they otherwise wouldn't be.

Unfortunately Unity's built in shadows aren't using the latest shadowing techniques. They're essentially using the same techniques games were 10 years ago, with some optimizations to the technique made about 4~5 years ago so the same effect would be cheaper (that could have been, and probably was being done before that by other games). If you want better shadow quality in Unity, you either need to upgrade to the HDRP, or try something like the Next Gen Soft-Shadows asset on the store.
https://assetstore.unity.com/packages/vfx/shaders/next-gen-soft-shadows-137380

Note. In extreme cases like a directional light facing straight down on a box, even the HDRP or that asset will likely still have some artifacts like you're seeing. There just isn't a complete solution for that case.

 

Sorry... that page seems to be missing!

 

The original page that was linked to can be found here:
https://docs.unity3d.com/2019.2/Documentation/Manual/ShadowOverview.html

It seems they've broken up the documentation into multiple pages for the latest documentation.
https://docs.unity3d.com/Manual/Shadows.html

 

In some ways path tracing is actually worse than shadow mapping for this specific case. Vertex normals and the resulting interpolated normal on the face is an illusion, and it's entirely possible and even expected that the interpolated normal can be facing towards the light in places where the actual surface is facing away from it. With path tracing producing accurate shadows, this can lead to situations like above. For non-realtime rendering this is one of the reasons why there's a heavy reliance on very high polygon or b-spline based surfaces. For realtime rendering using Phong tessellation can help alleviate this problem.

 

I'm sorry, I deleted my post because it seemed to me that I was probably making a basic mistake and I have to search the forum ...
This is path-tracing:

This is unity native Sphere object and Directional light. It only improves if I increase the angular diameter of the directional light.

 

Wow!

 

As an explanation what the problem is, this link goes into it a bit, along with describing what was done to minimize the issue for Bakery, a Unity lightmap baking asset that uses path tracing.

https://ndotl.wordpress.com/2018/08/29/baking-artifact-free-lightmaps/#leaks

 

Thanks for link, but this is not baked shadows, this is real-time path-tracig.

 

Bakery is an offline path tracer. The problem is the same, only the output is different.

You can't fix the problem with the technique described in that link, though Unity could if they were inclined to modify their ray tracing shaders to use the same work around. However the tessellation shader should produce the same results, assuming it works with HDRP's ray tracing.

 

Well, the section I linked to is purely about leaks due to UV seams, but the section just afterward goes into general raytraced shadow problems.
https://ndotl.wordpress.com/2018/08/29/baking-artifact-free-lightmaps/#shadowterm

 

So the only way to eliminate this feature is to find a shader that will have better features?
Edit: It is interesting. This is a scene with ray-tracing (not path-tracing) but the type of light is the same-directional, angular diameter 0.55.

But if I try to turn on raytraced shadows for this light:


The implementation of ray-tracing and path-tracing is probably not finished yet.
O.K. now we have to find a way around it so that we can use it already in this state. Probably a different lighting scenario.

 

There's no real difference between "ray tracing" and "path tracing" because they're not separate things. Path tracing is a specific form of ray tracing. Anyone who tells you they're "totally different things" is really just confused by the fact so many different rendering techniques are under the umbrella of ray tracing and aren't given a specific name. It's like arguing that an apple and a Honeycrisp are totally different things ... a Honeycrisp is a specific type of apple, but still an apple.

Even Unity's own documentation says the same thing in the first line!
https://docs.unity3d.com/Packages/c...ion@10.4/manual/Ray-Tracing-Path-Tracing.html

One thing Unity's documentation leaves out is each recursive ray's direction is randomly scattered based on the roughness of the surface. Also "reflective" in this specific context includes diffuse surfaces.

Really all ray tracing is, is calculating a ray through some set of geometry / shape data and finding the points of collision between the two points. This can be used to render an unlit object by tracing from the camera to some arbitrary point in the distance to find the closest surface, or between a surface position and a light to see if there are any other surfaces between it and the light for shadows. Unity's "ray tracing" is doing the later, but still using rasterization to find the surface. Except for ray traced reflections and refractions, which are using rasterization to find the first surface, and then ray tracing the same scene data to find the next surface position.

 

In practice, the difference between path tracing and ray tracing is now that- for ray tracing "without path tracing" I can turn off raytraced shadows for directional light and the artifacts in the shadows are gone.
This option has no effect in ray tracing with enabled path tracing and problems remain.

Ray tracing and path tracing give such very different results that I also considered them to be two different technologies...

 

Hi. I had the same problem but what seemed to solve it for me was Ray Bias under RayTrace Setting in the Volume Overrides.

 

Hi, thanks for the reply but unfortunately it doesn't work. I will try to install a newer version of Unity and try again.