acdream/tests/AcDream.App.Tests/Rendering/UnifiedFloodTests.cs

using System;
using System.Numerics;
using AcDream.App.Rendering;
using Xunit;

namespace AcDream.App.Tests.Rendering;

public class UnifiedFloodTests
{
    // Shared building fixture: a building cell whose interior is at Y >= 5.
    // The exit portal faces -Y (Normal=(0,-1,0)); interior is where dot<=0 -> Y>=5 (InsideSide=1).
    // The outdoor camera is at Y=-3, which is the OUTDOOR side (Y<5).
    // OutdoorCellNode.Build flips InsideSide to 0 so the outdoor camera (dot>=0 i.e. Y<5) passes
    // the side test and the flood reaches the building.
    private static LoadedCell MakeBuildingCell(uint cellId)
    {
        var building = new LoadedCell { CellId = cellId, SeenOutside = true };
        building.WorldTransform = Matrix4x4.Identity;
        building.InverseWorldTransform = Matrix4x4.Identity;
        building.Portals.Add(new CellPortalInfo(0xFFFF, 0, 0, 0));
        // InsideSide=1: interior where (0,-1,0)·p+5 <= 0 -> Y>=5 (the building body is at Y>=5).
        building.ClipPlanes.Add(new PortalClipPlane { Normal = new Vector3(0, -1, 0), D = 5f, InsideSide = 1 });
        building.PortalPolygons.Add(new[]
        {
            new Vector3(-1, 5, 0), new Vector3(1, 5, 0), new Vector3(1, 5, 2), new Vector3(-1, 5, 2)
        });
        return building;
    }

    [Fact]
    public void Build_RootedAtOutdoorNode_FloodsIntoBuilding()
    {
        var building = MakeBuildingCell(0xA9B40170);
        var node = OutdoorCellNode.Build(0xA9B40031, new[] { building });
        LoadedCell? Lookup(uint id) => (id & 0xFFFFu) == 0x0170 ? building : null;

        var eye = new Vector3(0, -3, 1);
        var view = Matrix4x4.CreateLookAt(eye, new Vector3(0, 5, 1), Vector3.UnitZ);
        var proj = Matrix4x4.CreatePerspectiveFieldOfView(MathF.PI / 3f, 16f / 9f, 1f, 5000f);

        var frame = PortalVisibilityBuilder.Build(node, eye, Lookup, view * proj);

        Assert.Contains(0xA9B40031u, frame.OrderedVisibleCells); // the outdoor node itself
        Assert.Contains(0xA9B40170u, frame.OrderedVisibleCells); // flooded into the building
    }

    [Fact]
    public void Build_OutdoorBuildingCycle_Terminates()
    {
        // Building's exit portal reciprocally points back near the node; assert Build
        // returns (does not hang) and the visible set is bounded/small.
        var building = MakeBuildingCell(0xA9B40170);
        var node = OutdoorCellNode.Build(0xA9B40031, new[] { building });
        LoadedCell? Lookup(uint id) => (id & 0xFFFFu) == 0x0170 ? building
                                     : (id & 0xFFFFu) == 0x0031 ? node : null;
        var eye = new Vector3(0, -3, 1);
        var view = Matrix4x4.CreateLookAt(eye, new Vector3(0, 5, 1), Vector3.UnitZ);
        var proj = Matrix4x4.CreatePerspectiveFieldOfView(MathF.PI / 3f, 16f / 9f, 1f, 5000f);

        var frame = PortalVisibilityBuilder.Build(node, eye, Lookup, view * proj);
        Assert.True(frame.OrderedVisibleCells.Count < 10); // bounded, no runaway
    }

    // Step A (cutover): rooting at the outdoor node must seed OutsideView with the FULL-SCREEN NDC
    // quad so DrawLandscapeThroughOutsideView draws the landscape as the node's shell. Without this
    // the outdoor-root frame would have OutsideViewSlices.Length==0 -> TerrainMode.Skip -> no terrain.
    [Fact]
    public void Build_RootedAtOutdoorNode_SeedsFullScreenOutsideView()
    {
        var building = MakeBuildingCell(0xA9B40170);
        var node = OutdoorCellNode.Build(0xA9B40031, new[] { building });
        LoadedCell? Lookup(uint id) => (id & 0xFFFFu) == 0x0170 ? building : null;

        var eye = new Vector3(0, -3, 1);
        var view = Matrix4x4.CreateLookAt(eye, new Vector3(0, 5, 1), Vector3.UnitZ);
        var proj = Matrix4x4.CreatePerspectiveFieldOfView(MathF.PI / 3f, 16f / 9f, 1f, 5000f);

        var frame = PortalVisibilityBuilder.Build(node, eye, Lookup, view * proj);

        Assert.False(frame.OutsideView.IsEmpty);
        // The union bounds of OutsideView must cover the whole NDC viewport (a full-screen quad),
        // so ClipFrameAssembler yields TerrainMode != Skip and the terrain draws everywhere.
        Assert.Equal(-1f, frame.OutsideView.MinX, 3);
        Assert.Equal(-1f, frame.OutsideView.MinY, 3);
        Assert.Equal(1f, frame.OutsideView.MaxX, 3);
        Assert.Equal(1f, frame.OutsideView.MaxY, 3);
    }

    // Pure-outdoor regression guard (spec section 10): an outdoor node with NO nearby buildings must
    // resolve to exactly {node} with a full-screen OutsideView -> full-screen terrain, no interior
    // cells, byte-for-byte today's open-world draw. Visual-gate the open field, not just the cottage.
    [Fact]
    public void Build_EmptyOutdoorNode_FullScreenOutsideView_OnlyNodeVisible()
    {
        var node = OutdoorCellNode.Build(0xA9B40031, Array.Empty<LoadedCell>());
        Assert.Empty(node.Portals); // no doorways

        var eye = new Vector3(0, -3, 1);
        var view = Matrix4x4.CreateLookAt(eye, new Vector3(0, 5, 1), Vector3.UnitZ);
        var proj = Matrix4x4.CreatePerspectiveFieldOfView(MathF.PI / 3f, 16f / 9f, 1f, 5000f);

        var frame = PortalVisibilityBuilder.Build(node, eye, _ => null, view * proj);

        Assert.Equal(new[] { 0xA9B40031u }, frame.OrderedVisibleCells); // only the node
        Assert.False(frame.OutsideView.IsEmpty);
        Assert.Equal(-1f, frame.OutsideView.MinX, 3);
        Assert.Equal(1f, frame.OutsideView.MaxX, 3);
    }
}