From 3618c136f74d8a50e7b91aec3f6aacd7da76b51e Mon Sep 17 00:00:00 2001
From: mcrcortex <18544518+MCRcortex@users.noreply.github.com>
Date: Mon, 2 Dec 2024 18:27:18 +1000
Subject: [PATCH] New mesher

---
 .../voxy/client/core/util/ScanMesher2D.java   | 145 ++++++++++++++++++
 1 file changed, 145 insertions(+)
 create mode 100644 src/main/java/me/cortex/voxy/client/core/util/ScanMesher2D.java

diff --git a/src/main/java/me/cortex/voxy/client/core/util/ScanMesher2D.java b/src/main/java/me/cortex/voxy/client/core/util/ScanMesher2D.java
new file mode 100644
index 00000000..44a56a10
--- /dev/null
+++ b/src/main/java/me/cortex/voxy/client/core/util/ScanMesher2D.java
@@ -0,0 +1,145 @@
+package me.cortex.voxy.client.core.util;
+
+public class ScanMesher2D {
+    // is much faster if implemented inline into parent
+    private long[] rowData = new long[32];
+    private int[] rowLength = new int[32];//How long down does a row entry go
+    private int[] rowDepth = new int[32];//How many rows does it cover
+    private int rowBitset = 0;
+
+    int currentIndex = 0;
+    int currentSum = 0;
+    long currentData = 0;
+
+    //Two different ways to do it, scanline then only merge on change, or try to merge with previous row at every step
+    // or even can also attempt to merge previous but if the lengths are different split the current one and merge to previous
+    public void putNext(long data) {
+        int thisIdx = (this.currentIndex++)&31;//Mask to current row, but keep total so can compute actual indexing
+
+        //If we are on the zero index, ignore it as we are going from empty state to maybe something state
+        // setup data
+        if (thisIdx == 0) {
+            //If the previous data is not zero, that means it was not merge-able, so emit it at the pos
+            if (this.currentData!=0) {
+                if ((this.rowBitset&(1<<31))!=0) {
+                    emitQuad(this.rowLength[31], this.rowDepth[31], this.rowData[31]);
+                }
+                this.rowBitset |= 1<<31;
+                this.rowLength[31] = this.currentSum;
+                this.rowDepth[31] = 1;
+                this.rowData[31] = this.currentData;
+            }
+
+            //Set the data to the first element
+            this.currentData = data;
+            this.currentSum = 0;
+        }
+
+        //If we are the same as last data increment
+        if (data == this.currentData) {
+            this.currentSum++;
+            //If we merge, then just continue
+            this.mergeCurrentIfPossibleOrEmit(thisIdx);
+            return;
+        }
+
+        //write out previous data
+        if (this.currentData != 0) {
+            int prev = thisIdx-1;//We need to write in the previous entry
+            this.rowDepth[prev] = 1;
+            this.rowLength[prev] = this.currentSum;
+            this.rowData[prev] = this.currentData;
+            this.rowBitset |= 1<<prev;
+        }
+
+
+        this.currentData = data;
+        this.currentSum = 1;
+
+        this.mergeCurrentIfPossibleOrEmit(thisIdx);
+    }
+
+    private boolean mergeCurrentIfPossibleOrEmit(int index) {
+        boolean isSet = (this.rowBitset&(1<<index))!=0;
+        //Greadily merge with previous row if possible
+        if (this.currentData != 0 &&//Ignore sentinel empty
+                isSet &&
+                this.rowLength[index] == this.currentSum &&
+                this.rowData[index] == this.currentData) {//Can merge with previous row
+            this.rowDepth[index]++;
+            this.currentSum = 0;//Clear sum since we went down
+            this.currentData = 0;//Zero is sentinel value for absent
+            return true;
+        }
+
+        if (isSet) {
+            this.emitQuad(this.rowLength[index], this.rowDepth[index], this.rowData[index]);
+            this.rowBitset &= ~(1<<index);
+        }
+
+        return false;
+    }
+
+    private boolean attemptMerge(int index, int length, long data) {
+        if ((this.rowBitset & (1 << index)) != 0 &&//Entry in previous bitset
+                this.rowLength[index] == length &&//If previous row merged length matches current
+                this.rowData[index] == data) {//If the previous row entry data matches
+            this.rowDepth[index]++;//Increment the depth
+            return true;
+        }
+        return false;
+    }
+
+    //Emits quads that exist at the mask pos and clear
+    private void emitRanged(int msk) {
+        {//Emit quads that cover the previous indices
+            int rowSet = this.rowBitset&msk;
+            while (rowSet!=0) {//Need to emit quads that would have skipped, note that this does not include the current index
+                int index = Integer.numberOfLeadingZeros(rowSet);
+                rowSet &= ~Integer.lowestOneBit(rowSet);
+
+                //Emit the quad, dont need to clear the data since it not existing in the bitmask is implicit no data
+                this.emitQuad(this.rowLength[index], this.rowDepth[index], this.rowData[index]);
+            }
+            this.rowBitset &= ~msk;
+        }
+    }
+
+    protected void emitQuad(int length, int width, long data) {
+        System.err.println("Quad, length: " + length + " width:  " + width + " data: " + data );
+    }
+
+    public static void main(String[] args) {
+        long[] sample = new long[32*32];
+
+        sample[0] = 1;
+        sample[1] = 1;
+        sample[2] = 1;
+        sample[3] = 1;
+        sample[4] = 2;
+        sample[5] = 2;
+        sample[6] = 2;
+        sample[7] = 2;
+        sample[0+32*1] = 1;
+        sample[1+32*1] = 1;
+        sample[2+32*1] = 1;
+        sample[3+32*1] = 1;
+        sample[4+32*1] = 2;
+        sample[5+32*1] = 2;
+        sample[6+32*1] = 2;
+        sample[7+32*1] = 2;
+        sample[31+32*0] = 6;
+        sample[31+32*1] = 6;
+        sample[31+32*2] = 7;
+        sample[31+32*3] = 8;
+        var mesher = new ScanMesher2D();
+        int j = 0;
+        for (long i : sample) {
+            if (j%32 == 0) {
+                System.out.println("row");
+            }
+            mesher.putNext(i);
+            j++;
+        }
+    }
+}