PortalRenderer.cs

using UnityEngine;
using UnityEngine.Rendering;

/// <summary>
/// Starts the recursive portal rendering process, taking into account portal occlusion volumes.
/// </summary>
public class PortalRenderer : MonoBehaviour
{
    private PortalOcclusionVolume[] portalOcclusionVolumes;

    [SerializeField] private Camera portalCamera;
    [SerializeField] private int maxRecursions = 2;
    [SerializeField] private LayerMask noCloneMask;
    [SerializeField] private LayerMask renderCloneMask;

    /// <summary>
    /// Debug read only: Indicates the total amount of recursive renders performed by portals this frame.
    /// </summary>
    public int debugTotalRenderCount;
    /// <summary>
    /// Debug read only: Indicates how many portal renders were due to being directly visible by the player.
    /// Use this field to debug the size of portal occlusion volumes.
    /// </summary>
    public int debugDirectRenderCount;

    private void OnEnable()
    {
        RenderPipelineManager.beginFrameRendering += RenderPipelineManagerOnBeginFrameRendering;
        RenderPipelineManager.endFrameRendering += RenderPipelineManagerOnEndFrameRendering;
    }

    private void OnDisable()
    {
        RenderPipelineManager.beginFrameRendering -= RenderPipelineManagerOnBeginFrameRendering;
        RenderPipelineManager.endFrameRendering -= RenderPipelineManagerOnEndFrameRendering;
    }

    private void Start()
    {
        portalOcclusionVolumes = FindObjectsOfType<PortalOcclusionVolume>();
    }

    /// <summary>
    /// Note: Does not support multiple cameras. Renders with mainCamera as reference.
    /// Multi camera support easily possible!
    /// </summary>
    private void RenderPipelineManagerOnBeginFrameRendering(ScriptableRenderContext context, Camera[] cameras)
    {
        // Find the current occlusion volume

        PortalOcclusionVolume currentOcclusionVolume = null;
        foreach (var portalOcclusionVolume in portalOcclusionVolumes)
        {
            if (portalOcclusionVolume.PositionInVolume(GameManager.Instance.MainCamera.transform.position))
            {
                currentOcclusionVolume = portalOcclusionVolume;
            }
        }

        // Render portals in occlusion volume

        if (currentOcclusionVolume == null)
            return;

        var mainCamera = GameManager.Instance.MainCamera;
        var mainCameraTransform = mainCamera.transform;
        var cameraPlanes = GeometryUtility.CalculateFrustumPlanes(mainCamera);

        debugTotalRenderCount = 0;
        debugDirectRenderCount = 0;

        foreach (var portal in currentOcclusionVolume.Portals)
        {
            if (!portal.ShouldRender(cameraPlanes))
                continue;

            portal.RenderViewthroughRecursive(
                mainCameraTransform.position,
                mainCameraTransform.rotation,
                out _,
                out _,
                out var renderCount,
                context,
                portalCamera,
                0,
                maxRecursions,
                currentOcclusionVolume,
                noCloneMask,
                renderCloneMask);

            debugTotalRenderCount += renderCount;
            debugDirectRenderCount++;
        }
    }

    private void RenderPipelineManagerOnEndFrameRendering(ScriptableRenderContext context, Camera[] cameras)
    {
        PortalRenderTexturePoolManager.Instance.ReleaseAll();
    }
}