feat(render): Phase A8.F — PortalProjection with GL near-plane clip (z>=-w)

tests/AcDream.App.Tests/Rendering/PortalProjectionTests.cs

@@ -0,0 +1,87 @@
+using System.Numerics;
+using AcDream.App.Rendering;
+using Xunit;
+
+namespace AcDream.App.Tests.Rendering;
+
+public class PortalProjectionTests
+{
+    // A simple GL-style perspective looking down -Z, camera at origin.
+    private static Matrix4x4 ViewProj()
+    {
+        var view = Matrix4x4.CreateLookAt(Vector3.Zero, new Vector3(0, 0, -1), Vector3.UnitY);
+        var proj = Matrix4x4.CreatePerspectiveFieldOfView(1.0f, 1.0f, 0.1f, 1000f);
+        return view * proj;
+    }
+
+    [Fact]
+    public void Project_QuadInFront_ProducesNdcInsideViewport()
+    {
+        // A 2x2 quad at z=-5 (in front), cell-local == world (identity transform).
+        var poly = new[]
+        {
+            new Vector3(-1, -1, -5), new Vector3(1, -1, -5), new Vector3(1, 1, -5), new Vector3(-1, 1, -5),
+        };
+        var r = PortalProjection.ProjectToNdc(poly, Matrix4x4.Identity, ViewProj());
+        Assert.True(r.Length >= 3);
+        foreach (var v in r)
+        {
+            Assert.InRange(v.X, -1.001f, 1.001f);
+            Assert.InRange(v.Y, -1.001f, 1.001f);
+        }
+    }
+
+    [Fact]
+    public void Project_QuadFullyBehind_ReturnsEmpty()
+    {
+        var poly = new[]
+        {
+            new Vector3(-1, -1, 5), new Vector3(1, -1, 5), new Vector3(1, 1, 5), new Vector3(-1, 1, 5),
+        };
+        var r = PortalProjection.ProjectToNdc(poly, Matrix4x4.Identity, ViewProj());
+        Assert.True(r.Length < 3);
+    }
+
+    [Fact]
+    public void Project_QuadStraddlingCamera_ClipsWithoutInversion()
+    {
+        // Spans from behind (z=+2) to in front (z=-5). Must clip to the in-front part,
+        // never produce a wildly out-of-range inverted vertex.
+        var poly = new[]
+        {
+            new Vector3(-1, -1, 2), new Vector3(1, -1, -5), new Vector3(1, 1, -5), new Vector3(-1, 1, 2),
+        };
+        var r = PortalProjection.ProjectToNdc(poly, Matrix4x4.Identity, ViewProj());
+        Assert.True(r.Length >= 3);
+        foreach (var v in r)
+        {
+            // A corner a few cm in front of the eye and ~1 m to the side genuinely
+            // projects large (~±37 NDC) but finite. ±50 still catches the ±7852
+            // perspective-inversion blow-up the old w-clip produced.
+            Assert.InRange(v.X, -50f, 50f); // bounded — no inversion blow-up
+            Assert.InRange(v.Y, -50f, 50f);
+        }
+    }
+
+    [Fact]
+    public void Project_QuadStraddlingCamera_DownstreamIntersectionIsValidOnScreen()
+    {
+        var poly = new[]
+        {
+            new Vector3(-1, -1, 2), new Vector3(1, -1, -5), new Vector3(1, 1, -5), new Vector3(-1, 1, 2),
+        };
+        var projected = PortalProjection.ProjectToNdc(poly, Matrix4x4.Identity, ViewProj());
+        Assert.True(projected.Length >= 3);
+
+        // The viewport region (NDC [-1,1]^2), same as CellView.FullScreen()'s single polygon.
+        var viewport = CellView.FullScreen().Polygons[0].Vertices;
+        var onScreen = ScreenPolygonClip.Intersect(projected, viewport);
+
+        Assert.True(onScreen.Length >= 3); // a non-empty visible region survives
+        foreach (var v in onScreen)
+        {
+            Assert.InRange(v.X, -1.001f, 1.001f);
+            Assert.InRange(v.Y, -1.001f, 1.001f);
+        }
+    }
+}