How to soft mask an entire 3D world at the radius edge of a sphere

Unity Engine
, , , , , , ,
1

I’m working with a scene wherein I need to mask off the entire 3D environment (about 300m across) using whatever technique meets requirements and is performant for VR. The effect should be able to taper/fade off and should have a pattern/noise or texture overlay. I am currently working with a spherical shape/volume to graduate the environment off to black. However this still leaves a silhouette against the skybox, where the camera can see the blackened edges of the environment. The Stencil buffer wont work for this because it won’t allow for soft radius fading (to my knowledge). The platform is the Quest 3 headset so I’m hesitant to overcomplicate how I might solve this problem, i.e. adding more cameras and producing rendertextures. In the image you can see I’ve got the tapering off to blackness working, but how might I re-use that for alpha/opacity as well (without touching any of the shaders of the environment)?

Any guidance or advice would be greatly appreciated.

Capture.PNG
Capture.PNG1234×821 107 KB

2

The first thing that come to my mind is to use a dithered alpha value with alpha clip.
The current black part would be clipped away an not rendered, the gradient would use the dithering to “fade”.

3

Thats not a bad idea. Maybe what I’m trying to do might be an impossibility. Right now that black area is just a color overlay. It’s a screen space URP render feature that is being transformed to world space and projected down over the world. How I would dither and alpha clip within this current setup is something I’m struggling with. I need to accomplish this without touching any of the environment shaders for the world.

4

Ah, without modifying the shaders of the objects, it is more tricky I guess …

The other solution would be to slightly modify your current renderer feature to project the skybox cubemap instead of simply applying a black overlay. In that case the objects would be undistinguishable from the skybox.