LibGL: Move polygon clipping to `Clipper` class

This code has also been optimised to be much more memory
friendly by removing a _lot_ of extraneous copies. The result
is that, when profiled, it's around 8x faster than the previous
implementation.

Co-Authored-By: Ali Mohammad Pur <ali.mpfard@gmail.com>

1 files changed, 59 insertions, 0 deletions

diff --git a/Userland/Libraries/LibGL/Clipper.h b/Userland/Libraries/LibGL/Clipper.h
new file mode 100644
index 0000000000..5c2e5bb276
--- /dev/null
+++ b/Userland/Libraries/LibGL/Clipper.h
@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Vector.h>
+#include <LibGfx/Vector4.h>
+
+namespace GL {
+
+class Clipper final {
+    enum ClipPlane : u8 {
+        LEFT = 0,
+        RIGHT,
+        TOP,
+        BOTTOM,
+        NEAR,
+        FAR
+    };
+
+    static constexpr u8 NUMBER_OF_CLIPPING_PLANES = 6;
+    static constexpr u8 MAX_CLIPPED_VERTS = 6;
+
+    static constexpr FloatVector4 clip_planes[] = {
+        { -1, 0, 0, 1 }, // Left Plane
+        { 1, 0, 0, 1 },  // Right Plane
+        { 0, 1, 0, 1 },  // Top Plane
+        { 0, -1, 0, 1 }, // Bottom plane
+        { 0, 0, 1, 1 },  // Near Plane
+        { 0, 0, -1, 1 }  // Far Plane
+    };
+
+    static constexpr FloatVector4 clip_plane_normals[] = {
+        { 1, 0, 0, 1 },  // Left Plane
+        { -1, 0, 0, 1 }, // Right Plane
+        { 0, -1, 0, 1 }, // Top Plane
+        { 0, 1, 0, 1 },  // Bottom plane
+        { 0, 0, -1, 1 }, // Near Plane
+        { 0, 0, 1, 1 }   // Far Plane
+    };
+
+public:
+    Clipper() { }
+
+    void clip_triangle_against_frustum(Vector<FloatVector4>& input_vecs);
+    const Vector<FloatVector4, MAX_CLIPPED_VERTS>& clipped_verts() const;
+
+private:
+    bool point_within_clip_plane(const FloatVector4& vertex, ClipPlane plane);
+    FloatVector4 clip_intersection_point(const FloatVector4& vec, const FloatVector4& prev_vec, ClipPlane plane_index);
+
+private:
+    Vector<FloatVector4, MAX_CLIPPED_VERTS> m_clipped_verts;
+};
+
+}