How to use sprite mask with trail renderer?

Unity Engine
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1

Is there any way to use sprite mask on trail renderer? I only want my trail to visible when it is on some specific sprite renderer, sprite mask fits this description, too bad it isn’t worked with trail renderer :(. I’m making a 2d game and currently using URP in Unity 2020.

2

In the end, I use a second camera with a render texture to achieve this. First, create a camera and a raw image with the same size as my material, then output the camera view to the raw image through a render texture (I do this through code at runtime). Also, remember to set the culling mask of the camera to the trail renderer’s layer.

    private void Start()
    {
        renderTex = new RenderTexture(size.x, size.y, 0);
        renderTex.Create();
        camera = new GameObject("Window Camera", typeof(Camera)).GetComponent<Camera>(); // I create a new game object with a camera rather than add it to the current object because I need to set the camera's pos to (0, 0, -10).
        camera.transform.parent = transform;
        camera.transform.localPosition = new Vector3(0, 0, -10); // Offset the z coord so that the camera can see stuff
        // Set the camera to be 2d
        camera.orthographic = true;
        camera.orthographicSize = transform.localScale.x / 2;
        camera.cullingMask = LayerMask.GetMask("Your Layer Here");
        camera.forceIntoRenderTexture = true; // I don't really know if I need this line, but didn't test it yet.
        camera.targetTexture = renderTex;
        image = GetComponentInChildren<RawImage>();
        image.texture = renderTex;
        image.canvas.worldCamera = camera;
    }
3

Hey, glad you figured out a workaround here.

Your question has inspired me to add proper support for this, like we have for particle systems.
Hopefully landing in 2022.1!

4

Just to confirm, this has now landed in 2022.1.0a7 :slight_smile:

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5

Hi,

I installed Unity version 2022.1.0b7 which includes this function but it’s not working the same way as on particles. For simplicity I created an object with a particle system and a trail renderer both set to ‘Visible outside mask’ but it seems the trail renderer ignores the mask. Is there anything else I should set for it to work?

Thanks in advance

7895149--1005427--ss.png

6

Hard to say with just the picture. The shader/material used is important. It needs to be compatible, such as Sprites/Default.

If that doesn’t explain it, a bug report would be appreciated!

7

Hi. There is a way to make the trail render as a mask of an image? I want an “eraser” effect but mixed with the trail effect, so the “erased” part will be reconstructed after a while. Thank you.

8

Where is this setting located? I can’t seem to find it on my Trail Renderer component… Neither can I get the code example to work. Help would be greatly appreciated

9

There should be a new “Mask Interaction” property in the Trail Renderer Inspector.

8150129--1058684--trail.png

If it’s not there, either you’re on the wrong version, or I told you the wrong version :slight_smile:

1 Like
10

Thank you!

1 Like
11

Hi Richard,
Is this then also something that can be added to LineRenderer? That would be wonderful for us and future generations :slight_smile: Thank you.

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12

It’s already there. When I added it to the TrailRenderer, i added it to the LineRenderer at the same time.

Available in 2022.2 and newer.

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13

Can this backport to 2021.3? Really need this feature when render TrailRenderers in UI.

14

Sorry, but no, we won’t be backporting this.