Simple Unity Collider Voxelizer

VoxelGenerator.cs

using System.Collections.Generic;
using UnityEngine;

namespace VertexFragment
{
    /// <summary>
    /// Generates a list of voxel points for a given collider.
    /// </summary>
    public static class VoxelGenerator
    {
        /// <summary>
        /// Returns an empty list if no valid collider is found attached to the game object.
        /// </summary>
        /// <param name="go"></param>
        /// <param name="isConcave"></param>
        /// <param name="xSlices"></param>
        /// <param name="ySlices"></param>
        /// <param name="zSlices"></param>
        /// <returns></returns>
        public static List<Vector3> Voxelize(GameObject go, bool isConcave, int xSlices, int ySlices, int zSlices)
        {
            if (go == null)
            {
                return new List<Vector3>();
            }

            if (isConcave)
            {
                return VoxelizeConcave(go.GetComponent<MeshCollider>(), xSlices, ySlices, zSlices);
            }
            else
            {
                return VoxelizeConvex(go.GetComponent<Collider>(), xSlices, ySlices, zSlices);
            }
        }

        /// <summary>
        /// Voxelizes a concave collider, which must be done using a <see cref="MeshCollider"/>.
        /// </summary>
        /// <param name="collider"></param>
        /// <param name="xSlices"></param>
        /// <param name="ySlices"></param>
        /// <param name="zSlices"></param>
        /// <returns></returns>
        public static List<Vector3> VoxelizeConcave(MeshCollider collider, int xSlices, int ySlices, int zSlices)
        {
            List<Vector3> voxels = new List<Vector3>(xSlices * ySlices * zSlices);

            if (collider == null)
            {
                return voxels;
            }

            bool prevConvex = collider.convex;
            collider.convex = false;

            var bounds = collider.bounds;

            xSlices = (xSlices <= 0) ? 1 : xSlices;
            ySlices = (xSlices <= 0) ? 1 : ySlices;
            zSlices = (xSlices <= 0) ? 1 : zSlices;

            float xStep = bounds.size.x / xSlices;
            float yStep = bounds.size.y / ySlices;
            float zStep = bounds.size.z / zSlices;

            for (int iz = 0; iz < zSlices; ++iz)
            {
                for (int iy = 0; iy < ySlices; ++iy)
                {
                    for (int ix = 0; ix < xSlices; ++ix)
                    {
                        Vector3 voxelCenter = new Vector3(
                            bounds.min.x + (xStep * (0.5f + ix)),
                            bounds.min.y + (yStep * (0.5f + iy)),
                            bounds.min.z + (zStep * (0.5f + iz)));

                        voxelCenter = collider.gameObject.transform.InverseTransformPoint(voxelCenter);

                        if (IsPointInCollider(collider, voxelCenter))
                        {
                            voxels.Add(voxelCenter);
                        }
                    }
                }
            }

            if (voxels.Count == 0)
            {
                // Just in case we somehow failed to generate a single point within the mesh.
                voxels.Add(bounds.center);
            }

            collider.convex = prevConvex;

            return voxels;
        }

        /// <summary>
        /// Voxelizes a convex collider, which can be done with any collider.
        /// </summary>
        /// <param name="collider"></param>
        /// <param name="xSlices"></param>
        /// <param name="ySlices"></param>
        /// <param name="zSlices"></param>
        /// <returns></returns>
        public static List<Vector3> VoxelizeConvex(Collider collider, int xSlices, int ySlices, int zSlices)
        {
            List<Vector3> voxels = new List<Vector3>(xSlices * ySlices * zSlices);

            if (collider == null)
            {
                return voxels;
            }

            var bounds = collider.bounds;

            xSlices = (xSlices <= 0) ? 1 : xSlices;
            ySlices = (xSlices <= 0) ? 1 : ySlices;
            zSlices = (xSlices <= 0) ? 1 : zSlices;

            float xStep = bounds.size.x / xSlices;
            float yStep = bounds.size.y / ySlices;
            float zStep = bounds.size.z / zSlices;

            for (int iz = 0; iz < zSlices; ++iz)
            {
                for (int iy = 0; iy < ySlices; ++iy)
                {
                    for (int ix = 0; ix < xSlices; ++ix)
                    {
                        Vector3 voxelCenter = new Vector3(
                            bounds.min.x + (xStep * (0.5f + ix)),
                            bounds.min.y + (yStep * (0.5f + iy)),
                            bounds.min.z + (zStep * (0.5f + iz)));

                        voxelCenter = collider.gameObject.transform.InverseTransformPoint(voxelCenter);

                        voxels.Add(voxelCenter);
                    }
                }
            }

            return voxels;
        }



        /// <summary>
        /// Uses raycasts to check if the specified point is within the collider.
        /// </summary>
        /// <param name="collider"></param>
        /// <param name="point"></param>
        /// <param name="maxDistance"></param>
        /// <returns></returns>
        private static bool IsPointInCollider(Collider collider, Vector3 point, float maxDistance = 1000.0f)
        {
            Vector3[] directions = {
                Vector3.up,
                Vector3.down,
                Vector3.left,
                Vector3.right,
                Vector3.forward,
                Vector3.back
            };

            foreach (var direction in directions)
            {
                // If just one of the ray directions fail, then we are not inside the collider.
                if (!collider.Raycast(new Ray(point, direction), out _, maxDistance))
                {
                    return false;
                }
            }

            return true;
        }
    }
}