Adjust the size of a chunk section's bounding box in frustum checks

This should fix some rare issues with floating-point
precision at extreme angles. It also ensures that certain block
models (such as the Lectern) will still be rendered at the
furthest extents of a chunk section.

Author: jellysquid3

src/main/java/me/jellysquid/mods/sodium/client/render/chunk/occlusion/OcclusionCuller.java

@@ -177,8 +177,13 @@ private static int nearestToZero(int min, int max) {
         return clamped;
     }
 
+    // The bounding box of a chunk section must be large enough to contain all possible geometry within it. Block models
+    // can extend outside a block volume by +/- 1.0 blocks on all axis. Additionally, we make use of a small epsilon
+    // to deal with floating point imprecision during a frustum check (see GH#2132).
+    private static final float CHUNK_SECTION_SIZE = 8.0f /* chunk bounds */ + 1.0f /* maximum model extent */ + 0.125f /* epsilon */;
+
     public static boolean isOutsideFrustum(Viewport viewport, RenderSection section) {
-        return !viewport.isBoxVisible(section.getCenterX(), section.getCenterY(), section.getCenterZ(), 8.0f);
+        return !viewport.isBoxVisible(section.getCenterX(), section.getCenterY(), section.getCenterZ(), CHUNK_SECTION_SIZE);
     }
 
     private void init(Consumer<RenderSection> visitor,