uniquake/Assets/Scripts/Game/GameState.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Rendering;

public class GameState
{
    private readonly UniQuake uq;

    private GameObject worldGameObject;

    public GameState(UniQuake uniQuake)
    {
        uq = uniQuake;
    }

    public void Destroy()
    {
        DestroyWorld();
    }

    public void NewMap(BrushModel worldModel)
    {
        DestroyWorld();
        
        // DEBUG - we'll want to instantiate prefabs for each submodel and assign materials from a preset collection
        worldGameObject = new GameObject(worldModel.Name);
        for (int i = 0; i < worldModel.SubModelCount; ++i)
        {
            var subModel = worldModel.GetSubModel(i);
            var subModelGO = new GameObject($"SubModel_{i}");
            subModelGO.transform.SetParent(worldGameObject.transform);
            
            foreach (var surfaceMesh in subModel.SurfaceMeshes)
            {
                var meshGO = new GameObject(surfaceMesh.Mesh.name);
                meshGO.transform.SetParent(subModelGO.transform);

                var mf = meshGO.AddComponent<MeshFilter>();
                mf.sharedMesh = surfaceMesh.Mesh;

                var material = new Material(Shader.Find("Universal Render Pipeline/Simple Lit"));
                uint texNum = surfaceMesh.Texture.TextureNum;
                if (uq.GameAssets.TryGetTexture(texNum, out var texture))
                {
                    material.mainTexture = texture;
                }

                var mr = meshGO.AddComponent<MeshRenderer>();
                mr.sharedMaterial = material;
                mr.shadowCastingMode = ShadowCastingMode.Off;
                mr.receiveShadows = false;
                mr.lightProbeUsage = LightProbeUsage.Off;
                mr.reflectionProbeUsage = ReflectionProbeUsage.Off;
            }
        }
    }

    private void DestroyWorld()
    {
        if (worldGameObject != null)
        {
            Object.Destroy(worldGameObject);
            worldGameObject = null;
        }
    }
}