ColliderCreator.cs

using UnityEditor;
using UnityEngine;

namespace Assets.Scripts.Utilities
{
    public class ColliderCreator : MonoBehaviour
    {
        [Header("Gizmos")]
        public bool visualize = true;
        public Color gizmosColor = Color.white;

        [Header("Generation")]
        public bool generateCapsuleColliders = true;
        public bool generateBoxColliders = true;

#if UNITY_EDITOR
        private void OnDrawGizmos()
        {
            if (!visualize)
                return;

            // start at 1 (2nd child), first child is container for box colliders.
            for (int i = 1; i < transform.childCount; i++)
            {
                var target = transform.GetChild(i);

                // render capsule for this child.
                if (generateCapsuleColliders)
                {
                    DrawWireCapsule(target.position, target.rotation, target.localScale.x, target.localScale.y);
                }

                // render box for child inbetween this and next child.
                if (generateBoxColliders && i < transform.childCount - 1)
                {
                    var other = transform.GetChild(i + 1);

                    var position = (target.position + other.position) / 2f;
                    var size = new Vector3((target.localScale.x + other.localScale.x) / 2f, (target.localScale.y + other.localScale.y) / 2f, Vector3.Distance(target.position, other.position));

                    Matrix4x4 rotationMatrix = Matrix4x4.TRS(position, Quaternion.LookRotation(other.position - target.position), size);
                    Gizmos.matrix = rotationMatrix;

                    Gizmos.color = gizmosColor * 0.3f;
                    Gizmos.DrawCube(Vector3.zero, Vector3.one);

                    Gizmos.color = gizmosColor;
                    Gizmos.DrawWireCube(Vector3.zero, Vector3.one);

                    Gizmos.matrix = Matrix4x4.identity;
                }
            }
        }

        private void DrawWireCapsule(Vector3 position, Quaternion rotation, float radius, float height)
        {
            Handles.color = gizmosColor;
            Matrix4x4 angleMatrix = Matrix4x4.TRS(position, rotation, Handles.matrix.lossyScale);
            using (new Handles.DrawingScope(angleMatrix))
            {
                var pointOffset = (height - (radius * 2)) / 2;

                // draw sideways.
                Handles.DrawWireArc(Vector3.up * pointOffset, Vector3.left, Vector3.back, -180, radius);
                Handles.DrawLine(new Vector3(0, pointOffset, -radius), new Vector3(0, -pointOffset, -radius));
                Handles.DrawLine(new Vector3(0, pointOffset, radius), new Vector3(0, -pointOffset, radius));
                Handles.DrawWireArc(Vector3.down * pointOffset, Vector3.left, Vector3.back, 180, radius);
                // draw frontways.
                Handles.DrawWireArc(Vector3.up * pointOffset, Vector3.back, Vector3.left, 180, radius);
                Handles.DrawLine(new Vector3(-radius, pointOffset, 0), new Vector3(-radius, -pointOffset, 0));
                Handles.DrawLine(new Vector3(radius, pointOffset, 0), new Vector3(radius, -pointOffset, 0));
                Handles.DrawWireArc(Vector3.down * pointOffset, Vector3.back, Vector3.left, -180, radius);
                // draw center.
                Handles.DrawWireDisc(Vector3.up * pointOffset, Vector3.up, radius);
                Handles.DrawWireDisc(Vector3.down * pointOffset, Vector3.up, radius);

            }
        }
 #endif

    }
}