How can I only render world only within given boundaries?

Unity Engine
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1

Hello,

I would like to achieve a similar effect than the one done in “Unrailed!”, see video at given timestamp:

The idea is to divide the space in a cylinder from the space around it.
To render something in that cylinder and something else outside and to shrink it/expand it dynamically.

I asked “Unrailed!” dev team, but they don’t use Unity so we didn’t go into details…

I didn’t find a way to achieve that in Unity yet. Any idea?

2

Please note that meshed are “cut” in 3D by the cylinder!

3

You need to use a custom shader that hides or shows the fragment based on distance from a point.

This article talks about something similar.

1 Like
4

I knew this would come down to writing shaders! Man I really need to learn that sh*t.

Thanks a lot for the useful link, this is exactly what I was looking for!

This will actually allow me to start somewhere with the shaders, good stuff.

5

So I’m looking more into that today. Does that mean every mesh I’m going to try to cut will have to be set to transparent?

6

Not transparent, no. The clip() function works on opaque objects, it just skips rendering those pixels.

7

I’ve just read one of your posts in another thread:

I was wondering why it was so hardcore to start writing lit shaders with my HDRP project…
So I guess since I’m expected to use shader graphs, this is going to be impossible to implement. Right?

8

Nah, pretty simple to do in shader graph. This is one of the kind of things Shader Graph excels at.

Position Vector3 property, radius Vector1 property (or a single Vector4 for both). A position node set to world. A sphere mask node. Plug the world position, position property, and radius into the sphere mask, and direct the output into the master alpha. Then use a Vector1 to set the Alpha Threshold to 0.5 and you’re done.

To flip what part of the circle gets hidden, use a one minus node on the sphere mask output. You can use a bool property and a branch to select between the two versions.

9

Thanks I’ll try that.

The world position property has to be a fixed value right? This cannot be a moving gameobject position, right?

I guess this is the case with any shader anyway.

10

No! I can access shader’s properties using setFloat in the script!

OK I’ll give it a shot.

11

Wrote the base shader you described today. It works in editor and gives a pretty neat result. Thanks!

Now I need to rethink everything to use that :smile: