GradientBaker.cs

using System.Security.Cryptography.X509Certificates;
using UnityEditor;
using UnityEngine;

namespace SDFr
{
    public class GradientBaker : MonoBehaviour
    {

        public Texture3D sdfTexture;
        
        public float Sphere(Vector3 p, float r) {
            return p.magnitude - r ;
        }

        public float Box(Vector2 p, Vector2 b) {
            var d = new Vector2(Mathf.Abs(p.x),Mathf.Abs(p.y)) - b;
            return Vector2.Max(d, Vector2.zero).magnitude + Mathf.Min(Mathf.Max(d.x, d.y), 0f);
        }

        public float Distance(int xx, int yy, int zz)
        {
            //Example synthetic distance fields
            //float x = (float) xx / sdfTexture.width;
            //float y = (float) yy / sdfTexture.height;
            //float z = (float) zz / sdfTexture.depth;
            //return Mathf.Min(Box(new Vector2(x,y), new Vector2(.2f,.2f)), Circle(new Vector2(x+.5f, y), .2f));
            //return Mathf.Min(Sphere(new Vector3(x-.5f, y, z), .3f), Sphere(new Vector3(x+.5f, y, z), .3f));
          
            return sdfTexture.GetPixel(xx, yy, zz, 0).r;
        }
        
        [ContextMenu("Bake")]
        public void Bake()
        {

            Texture3D outTexture = new Texture3D(sdfTexture.width, sdfTexture.height, sdfTexture.depth, TextureFormat.RGBAFloat, false);
            //var center = new Vector3(sdfTexture.width/2f, sdfTexture.height/2f, sdfTexture.depth/2f);
            for (int z = 0; z < sdfTexture.depth; z++)
            {
                for (int y = 0; y < sdfTexture.height; y++)
                {
                    for (int x = 0; x < sdfTexture.width; x++)
                    {
                        var normal = new Vector3();
                        //var toCenter = (new Vector3(x, y, z) - center).normalized;
                        normal.x = Distance(x - 1, y, z) - Distance(x + 1, y, z);
                        normal.y = Distance(x, y - 1, z) - Distance(x, y + 1, z);
                        normal.z = Distance(x, y, z - 1) - Distance(x, y, z + 1);
                        //var tangent = Vector3.Cross(normal, toCenter);
                        //var tangent = normal - center;

                        if (x % 8 == 0 && y % 8 == 0 && z % 8 == 0)
                        {
                            Debug.Log(Distance(x - 1, y, z) - Distance(x + 1, y, z));
                            Debug.Log($@"{x},{y},{z}: {normal.x},{normal.y},{normal.z}");
                        }
                        
                        outTexture.SetPixel(x, y, z, new Color(normal.x, normal.y, normal.z));
                    }
                }
            }
            
            outTexture.Apply();
            AssetDatabase.CreateAsset(outTexture, "Assets/gradient.asset");
        }
    }
}