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Using the Geographically Accurate Sun Positioning to animate sun

Development Discussion Rendering
#1

Hi,

I’m trying to use the Geographically Accurate Sun Positioning, which is an early access function from 4.21, to animate the Sun’s position in a whole day.
My method is using a blueprint to change the time by adding seconds, as the method in the documentation page. https://docs.unrealengine.com/en-us/Engine/Rendering/LightingAndShadows/SunPositioner

The issue is while the sun angle is changing, I can see obvious shaking of the shadow edge, and sometimes wired shadow appears on my curtain beside the window, flashing. But when I manually rotate the directional light, the shadow is sharp enough with no shaking.

Any thoughts?

Thanks!!

#2

Got response from UDN, for reference if anyone need:

This is related to the resolution of the cascade shadow map (CSM). The default is 2048. I tested as Shadow scalability level 4 (Cinematic) and it was better (4096). I also forced it to 8192 with the r.Shadow.MaxCSMResolution console command and I was even better. Please note that those settings will have an impact on performance.