Add angle-based section visibility path occlusion (#2811)

This eliminates 8-13% of the rendered sections at higher render distances on average in testing, and correspondingly reduces graph search time by a similar amount.

common/src/main/java/net/caffeinemc/mods/sodium/client/render/chunk/occlusion/OcclusionCuller.java

@@ -61,10 +61,16 @@ private static void processQueue(Visitor visitor,
 
             {
                 if (useOcclusionCulling) {
+                    var sectionVisibilityData = section.getVisibilityData();
+
+                    // occlude paths through the section if it's being viewed at an angle where
+                    // the other side can't possibly be seen
+                    sectionVisibilityData &= getAngleVisibilityMask(viewport, section);
+
                     // When using occlusion culling, we can only traverse into neighbors for which there is a path of
                     // visibility through this chunk. This is determined by taking all the incoming paths to this chunk and
                     // creating a union of the outgoing paths from those.
-                    connections = VisibilityEncoding.getConnections(section.getVisibilityData(), section.getIncomingDirections());
+                    connections = VisibilityEncoding.getConnections(sectionVisibilityData, section.getIncomingDirections());
                 } else {
                     // Not using any occlusion culling, so traversing in any direction is legal.
                     connections = GraphDirectionSet.ALL;
@@ -79,6 +85,30 @@ private static void processQueue(Visitor visitor,
         }
     }
 
+    private static final long UP_DOWN_OCCLUDED = (1L << VisibilityEncoding.bit(GraphDirection.DOWN, GraphDirection.UP)) | (1L << VisibilityEncoding.bit(GraphDirection.UP, GraphDirection.DOWN));
+    private static final long NORTH_SOUTH_OCCLUDED = (1L << VisibilityEncoding.bit(GraphDirection.NORTH, GraphDirection.SOUTH)) | (1L << VisibilityEncoding.bit(GraphDirection.SOUTH, GraphDirection.NORTH));
+    private static final long WEST_EAST_OCCLUDED = (1L << VisibilityEncoding.bit(GraphDirection.WEST, GraphDirection.EAST)) | (1L << VisibilityEncoding.bit(GraphDirection.EAST, GraphDirection.WEST));
+
+    private static long getAngleVisibilityMask(Viewport viewport, RenderSection section) {
+        var transform = viewport.getTransform();
+        var dx = Math.abs(transform.x - section.getCenterX());
+        var dy = Math.abs(transform.y - section.getCenterY());
+        var dz = Math.abs(transform.z - section.getCenterZ());
+
+        var angleOcclusionMask = 0L;
+        if (dx > dy || dz > dy) {
+            angleOcclusionMask |= UP_DOWN_OCCLUDED;
+        }
+        if (dx > dz || dy > dz) {
+            angleOcclusionMask |= NORTH_SOUTH_OCCLUDED;
+        }
+        if (dy > dx || dz > dx) {
+            angleOcclusionMask |= WEST_EAST_OCCLUDED;
+        }
+
+        return ~angleOcclusionMask;
+    }
+
     private static boolean isSectionVisible(RenderSection section, Viewport viewport, float maxDistance) {
         return isWithinRenderDistance(viewport.getTransform(), section, maxDistance) && isWithinFrustum(viewport, section);
     }

common/src/main/java/net/caffeinemc/mods/sodium/client/render/chunk/occlusion/VisibilityEncoding.java

@@ -21,7 +21,7 @@ public static long encode(@NotNull VisibilitySet occlusionData) {
         return visibilityData;
     }
 
-    private static int bit(int from, int to) {
+    public static int bit(int from, int to) {
         return (from * 8) + to;
     }