Add workaround for fancy grass z-fighting

This only increases quad count from 780 KQ to 792 KQ on the complex savanna
scene.

2 files changed, 22 insertions, 0 deletions

diff --git a/src/main/java/makamys/neodymium/renderer/ChunkMesh.java b/src/main/java/makamys/neodymium/renderer/ChunkMesh.java
index 971c6f2..de14867 100644
--- a/src/main/java/makamys/neodymium/renderer/ChunkMesh.java
+++ b/src/main/java/makamys/neodymium/renderer/ChunkMesh.java
@@ -204,6 +204,20 @@ public class ChunkMesh extends Mesh {
     }
     
     private static void simplifyPlane(List<MeshQuad> planeQuads) {
+        // Exclude quads from merging if they have identical vertex positions to another quad.
+        // Workaround for z-fighting issue that arises when merging fancy grass and the overlay quad
+        // is a different dimension than the base quad.
+        for(int i = 0; i < planeQuads.size(); i++) {
+            MeshQuad a = planeQuads.get(i);
+            for(int j = i + 1; j < planeQuads.size(); j++) {
+                MeshQuad b = planeQuads.get(j);
+                if(a.isPosEqual(b)) {
+                    a.noMerge = true;
+                    b.noMerge = true;
+                }
+            }
+        }
+        
         MeshQuad lastQuad = null;
         // Pass 1: merge quads to create rows
         for(MeshQuad quad : planeQuads) {
diff --git a/src/main/java/makamys/neodymium/renderer/MeshQuad.java b/src/main/java/makamys/neodymium/renderer/MeshQuad.java
index 581e6f3..45ea73b 100644
--- a/src/main/java/makamys/neodymium/renderer/MeshQuad.java
+++ b/src/main/java/makamys/neodymium/renderer/MeshQuad.java
@@ -2,6 +2,7 @@ package makamys.neodymium.renderer;
 
 import java.io.DataOutputStream;
 import java.io.IOException;
+import java.util.Arrays;
 import java.util.Comparator;
 import java.util.Locale;
 import java.util.Map;
@@ -46,6 +47,7 @@ public class MeshQuad {
     public int[] cs = new int[4];
     // TODO normals?
     public boolean deleted;
+    public boolean noMerge;
     
     public Plane plane;
     public int offset;
@@ -195,6 +197,8 @@ public class MeshQuad {
     }
     
     public void tryToMerge(MeshQuad o) {
+        if(noMerge || o.noMerge) return;
+        
         if(isTranslatedCopyOf(o, true)) {
             int numVerticesTouching = 0;
             boolean[] verticesTouching = new boolean[4];
@@ -329,4 +333,8 @@ public class MeshQuad {
         XZ,
         YZ
     }
+
+    public boolean isPosEqual(MeshQuad b) {
+        return Arrays.equals(xs, b.xs) && Arrays.equals(ys, b.ys) && Arrays.equals(zs, b.zs);
+    }
 }