Cineversity

I have been having issues with soft shadows flickering . I am NOT using GI.  These are just renders through the standard renderer.

I have increased the shadow map size but it hasn’t eliminated the problem.

All the posts on Shadow flicker seem to be about GI flicker.

Any thoughts/

Thanks

TAK

A shadow map is really like an image that is being stretched across your scene from the point of the light.
That is probably the simplest explaination, but there is a lot more that goes into it.
Because of this you have many options to control the shadow maps that you create.

The map size is best used to control the quality of the map based on the surface area you need to cover.
This is usually dependent on the light’s angle / distance from the objects it is illuminating.

You then have sample radius, this option is used to control the base quality of the map, higher values will be more accurate, but also render slower.

then there is the bias, this offsets the shadow map on the surface.
Sometimes you can run into issues where an object casts shadows on itself.
These are times when you may need to increase the bias.

Note that these settings can also be animated…this is because your requirements may change depending on the animation, so you can always change the values to suite.

ie. a high bias value may work in one light position, but not another…so you can animate a transition between those values.

beyond that, scenes or images would help greatly

Hi TAK,

Patricks example is a nice introduction.

Let me explain that a little bit more. It is of course not a texture, it is a collection of points with information like a 3D net. A structure of points. The “map” size is pretty much the mount of “lines” or if you like rays that get “shot” into the scene to gather information if there is an shadow casting object or not. It does it not constantly, it does it with a distance. If an object is between two points, the information is not exact of course, and will be never 100% sharp like a ray tracing shadow.

The next object that would receive the shadow receive then a calculation among these points in space, hence the soft part. If you take a look to all the parameters, this model will make more sense. With most parameters you set the distance among the points as well the way it is interpolated.

It is an old technique from the time when computer had no real power, and it is a fake or simulation. All to save resource.

If an object moves now around or the light moves, perhaps both, the shadow casting object is between a specific set of points and then among a new set, there is not “smooth” change, but the softness makes you think there is. based on that, you might get flickering, nothing new or un-expected. It is fast and has its limitations.

I would really love if that map/texture example wouldn’t be used anymore (I’m glad Patrick introduced that is more complicated :o). The Image example has confused over a decade uncounted users and even some book authors use it, in this way the whole idea is not understood, and the parameters look cryptic of course.

I hope that makes it more clear and understand able. If you think you can just lower the distance among all points… well the calculation time goes up and the “non-light/Shadow” areas become sharper. My suggestion, if possible, use something else instead, seriously.

All the best

Sassi

Thanks gentlemen.  I’ve increased both the shadow map size and sampling.  Seems to have done the trick.  The issue is always render time.  Even just to a test or multiple tests to see if what I am doing is the right thing.  Fortunately I have a pretty speedy 12 core and lots of memory.

Hi TAK,

You’re welcome. I certainly think that a 12 core should please you :o)

Doing 3D renderings since 20 years, I have certainly more patience when I think back to the 24 hours for a 1024pixel wide rendering in the old days. Hehe. I recall that time and enjoy the power we have these days for such a little budget.

Have a great weekend

Sassi