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Parameters

Parameter	Description
lineTex	The AA texture used for rendering.
width	The width of the line.
points	List of points to build the line from.
colors	The colors to apply to each point. Must match the length of the points array or actualNumberOfPoints, whichever is lower and greater than zero.
actualNumberOfPoints	The total number of vertices to draw of the points array. Use this to keep a reusable buffer of point values without the need to resize frequently.

Description

Draw anti-aliased line specified with point array and width.

Note: Use HandleUtility.GetHandleSize where you might want to have constant screen-sized handles.

Note: To get an anti-aliased effect use a texture that is 1x2 pixels with one transparent white pixel and one opaque white pixel.

using UnityEditor;
using UnityEngine;

public class ArrowDrawer : MonoBehaviour
{
    public void DrawArrow(Color color, float arrowThickness, float lineThickness, float shorten, Vector3 start, Vector3 end)
    {
        var length = (end - start).magnitude;
        if (length < 0.001f)
            return;

        var forward = (end - start) / length;
        var right = Vector3.Cross(Vector3.up, forward).normalized;

        var width = arrowThickness * 0.5f;
        var height = arrowThickness * 0.7f;

        start += forward * shorten;
        end -= forward * shorten;

        var arrowHead = new Vector3[3]
        {
            end,
            end - forward * height + right * width,
            end - forward * height - right * width
        };

        var arrowLine = new Vector3[2]
        {
            start,
            end - forward * height
        };

        Handles.color = color;
        Handles.DrawAAPolyLine(lineThickness, 2, arrowLine);
        Handles.DrawAAConvexPolygon(arrowHead);
    }

    void OnDrawGizmos()
    {
        DrawArrow(Color.white, 1f, 3f, 0f, transform.position, transform.position + transform.TransformDirection(Vector3.forward) * 4f);
    }
}