Fast 2D lines

2D
1

Can anybody suggest a way to draw fast 2D lines? I need them in screenspace, not 3D world space, for a specialized UI element.

GL and LineRenderer are in 3D space, so I don’t think they will work for what I need to do.

2

Do you need to have lines drawn on the screen while 3D is going on in the background with a moving camera? If so, you can use GL or LineRenderer, but draw the lines in the camera’s coordinate space (use transform.TransformPoint to convert camera-relative points to world points).

If you just need lines with a static camera, you can probably just position the camera so that it sees the XY plane (ie, the plane where the Z coordinate is zero). It’s worth noting that you can use a Vector2 anywhere that a Vector3 is expected - it will be converted directly to a Vector3 with Z set to zero. This can simplify some 2D geometry tasks.

3

GL.LINES works fine, like this shows. As mentioned, just convert 2D/3D as necessary. I used ViewportToWorldPoint so I could use normalized viewport coords for the 2D points, but you could use another system like screen coordinates if you wanted to.

–Eric

4

I’m trying to do this with the LineRenderer and this is what I have so far:

    LineRenderer Line;

    void Start()
    {
        Line = GetComponent<LineRenderer>();
        Line.SetWidth(1, 1);
        Line.SetVertexCount(2);
        Line.material.color = Color.white;
    }
    void Update()
    {
        Vector3 from = Camera.current.ViewportToWorldPoint(new Vector2(10, 10));
        Vector3 to = Camera.current.ViewportToWorldPoint(new Vector2(50, 50));

        Line.SetPosition(0, from);
        Line.SetPosition(1, to);
    }

This doesn’t give me the desired result though. I just need to be able to draw a simple 2D line in XY coordinate space, with (0,0) being top left and (screen.width, screen.height) bottom right. What do I have to change to make it work? Thanks :slight_smile:

5

You’re using viewport space, but you actually want screen space.

–Eric

6

Thanks for your reply, Eric!

I changed it to

        Vector3 from = activeCam.ScreenToWorldPoint(new Vector3(10, 10, activeCam.nearClipPlane));
        Vector3 to = activeCam.ScreenToWorldPoint(new Vector3(50, 50, activeCam.nearClipPlane));

And that seems to work. Just passing in a Vector2(50, 50) doesn’t work.

Now I’m stuck on something else: the line must be 1 pixel wide.

Line.SetWidth(0.0001f, 0.0001f);

This gives me a 1 pixel line, but I just picked these values randomly. Do you have an idea on what value to use?

Thanks again :smile: