From c5b4e20787c14b125b1b42b1a017b97568a5ce7e Mon Sep 17 00:00:00 2001
From: James Seibel <jeseibel@gondtc.com>
Date: Sat, 21 Aug 2021 13:05:32 -0500
Subject: [PATCH] Add simple partially functioning frustum culling

---
 .../com/seibel/lod/render/LodRenderer.java    | 39 +++++++++++++---
 .../com/seibel/lod/render/RenderUtil.java     | 44 ++++++++++++++++++-
 2 files changed, 76 insertions(+), 7 deletions(-)

diff --git a/src/main/java/com/seibel/lod/render/LodRenderer.java b/src/main/java/com/seibel/lod/render/LodRenderer.java
index f2b3204ec..f7e92bae2 100644
--- a/src/main/java/com/seibel/lod/render/LodRenderer.java
+++ b/src/main/java/com/seibel/lod/render/LodRenderer.java
@@ -39,6 +39,7 @@ import com.seibel.lod.handlers.ReflectionHandler;
 import com.seibel.lod.objects.LevelPos;
 import com.seibel.lod.objects.LodDimension;
 import com.seibel.lod.objects.NearFarFogSettings;
+import com.seibel.lod.objects.RegionPos;
 import com.seibel.lod.proxy.ClientProxy;
 import com.seibel.lod.util.LodUtil;
 
@@ -67,7 +68,7 @@ import net.minecraft.util.math.vector.Vector3f;
  * This is where LODs are draw to the world.
  *
  * @author James Seibel
- * @version 8-20-2021
+ * @version 8-21-2021
  */
 public class LodRenderer
 {
@@ -318,14 +319,39 @@ public class LodRenderer
 
         if (vbos != null)
         {
+        	int rendered = 0;
+        	int skipped = 0;
+        	
+        	Vector3d cameraDir = mc.cameraEntity.getLookAngle();
+        	
+        	// used to determine what type of fog to render
+        	int halfWidth = vbos.length/2;
+        	int quarterWidth = vbos.length/4;
+        	
             for (int i = 0; i < vbos.length; i++)
             {
                 for (int j = 0; j < vbos.length; j++)
                 {
-                    setupFog(fogSettings.near.distance, fogSettings.near.quality);
-                    sendLodsToGpuAndDraw(vbos[i][j], modelViewMatrix);
+                	RegionPos vboPos = new RegionPos(i + lodDim.getCenterX() - lodDim.getWidth()/2, j + lodDim.getCenterZ() - lodDim.getWidth()/2);
+	            	if (RenderUtil.isRegionInViewFrustum(player.blockPosition(), cameraDir, vboPos.blockPos()))
+	            	{
+	                	if ((i > halfWidth - quarterWidth && i < halfWidth + quarterWidth) && (j > halfWidth - quarterWidth && j < halfWidth + quarterWidth))
+	                		setupFog(fogSettings.near.distance, fogSettings.near.quality);
+	                	else
+	                		setupFog(fogSettings.far.distance, fogSettings.far.quality);
+	                    
+	                	
+	            		sendLodsToGpuAndDraw(vbos[i][j], modelViewMatrix);
+	            		rendered++;
+	                }
+	            	else
+	            	{
+	            		skipped++;
+	            	}
                 }
             }
+            
+            ClientProxy.LOGGER.info(rendered + " - " + skipped);
         }
 
 
@@ -361,9 +387,10 @@ public class LodRenderer
         // end of internal LOD profiling
         profiler.pop();
     }
-
-
-    /**
+    
+    
+    
+	/**
      * This is where the actual drawing happens.
      *
      * @param buffers the buffers sent to the GPU to draw
diff --git a/src/main/java/com/seibel/lod/render/RenderUtil.java b/src/main/java/com/seibel/lod/render/RenderUtil.java
index a99d449d6..49108b987 100644
--- a/src/main/java/com/seibel/lod/render/RenderUtil.java
+++ b/src/main/java/com/seibel/lod/render/RenderUtil.java
@@ -22,14 +22,16 @@ import com.seibel.lod.handlers.LodConfig;
 import com.seibel.lod.util.LodUtil;
 
 import net.minecraft.client.Minecraft;
+import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.ChunkPos;
+import net.minecraft.util.math.vector.Vector3d;
 
 /**
  * This holds miscellaneous helper code
  * to be used in the rendering process.
  * 
  * @author James Seibel
- * @version 8-17-2021
+ * @version 8-21-2021
  */
 public class RenderUtil
 {
@@ -105,4 +107,44 @@ public class RenderUtil
 		
 		return numbLodsWide / (2 * mc.options.renderDistance);
 	}
+	
+	
+	/**
+	 * Returns true if one of the regions 4 corners is in front
+	 * of the camera.
+	 */
+	public static boolean isRegionInViewFrustum(BlockPos playerBlockPos, Vector3d cameraDir, BlockPos vboCenterPos)
+	{
+    	// convert the vbo position into a direction vector
+    	// starting from the player's position
+		Vector3d vboVec = new Vector3d(playerBlockPos.getX(), 0, playerBlockPos.getZ());
+		Vector3d playerVec = new Vector3d(vboCenterPos.getX(), vboCenterPos.getY(), vboCenterPos.getZ());
+		Vector3d vboCenterVec = playerVec.subtract(vboVec);
+		
+		
+    	int halfRegionWidth = LodUtil.REGION_WIDTH;
+    	
+    	Vector3d vboSeVec = new Vector3d(vboCenterVec.x + halfRegionWidth, 0, vboCenterVec.z + halfRegionWidth).normalize();
+    	Vector3d vboSwVec = new Vector3d(vboCenterVec.x - halfRegionWidth, 0, vboCenterVec.z + halfRegionWidth).normalize();
+    	Vector3d vboNwVec = new Vector3d(vboCenterVec.x - halfRegionWidth, 0, vboCenterVec.z - halfRegionWidth).normalize();
+    	Vector3d vboNeVec = new Vector3d(vboCenterVec.x + halfRegionWidth, 0, vboCenterVec.z - halfRegionWidth).normalize();
+    	
+    	return isNormalizedVectorInViewFrustum(vboSeVec, cameraDir) ||
+    			isNormalizedVectorInViewFrustum(vboSwVec, cameraDir) ||
+    			isNormalizedVectorInViewFrustum(vboNwVec, cameraDir) ||
+    			isNormalizedVectorInViewFrustum(vboNeVec, cameraDir);
+    	
+//    	return isNormalizedVectorInViewFrustum(vboCenterVec.normalize(), cameraDir);
+	}
+    
+	/**
+	 * Currently takes the dot product of the two vectors,
+	 * but in the future could do more complicated frustum culling tests.
+	 */
+    private static boolean isNormalizedVectorInViewFrustum(Vector3d objectVector, Vector3d cameraDir)
+	{
+    	// take the dot product
+    	double dot = objectVector.dot(cameraDir);
+    	return dot >= 0;
+	}
 }