From 623fc8c73de35bef0785f09bae8a3f607f8ed087 Mon Sep 17 00:00:00 2001
From: Wolfgang Draxinger <Wolfgang.Draxinger@draxit.de>
Date: Fri, 27 Apr 2012 20:43:08 +0200
Subject: qt_terr - a simple quadtree based terrain renderer with LOD

---
 samples/OpenGL/qt_terr/terragen.cpp | 138 ++++++++++++++++++++++++++++++++++++
 1 file changed, 138 insertions(+)
 create mode 100644 samples/OpenGL/qt_terr/terragen.cpp

(limited to 'samples/OpenGL/qt_terr/terragen.cpp')

diff --git a/samples/OpenGL/qt_terr/terragen.cpp b/samples/OpenGL/qt_terr/terragen.cpp
new file mode 100644
index 0000000..3b922a4
--- /dev/null
+++ b/samples/OpenGL/qt_terr/terragen.cpp
@@ -0,0 +1,138 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "terragen.h"
+
+// Some custom types and helper macros that
+// allow for a portable file to number variable
+// read procedure
+
+typedef uint8_t DUET[2];
+typedef uint8_t QUARTET[4];
+typedef uint8_t OCTET[8];
+
+#define DUET_TO_NUMBER(duet)		((duet[0]|duet[1]<<8))
+#define QUARTET_TO_NUMBER(quartet)	((quartet[0])|(quartet[1]<<8)|(quartet[2]<<16)|(quartet[3]<<24))
+
+int read_terrain(char *filename, double **pbuffer, int *width, int *height, double *scale)
+// [in] filename: path to the file to be read in
+// [out] pbuffer: address of new allocated data buffer
+// [out] width: width of the terrain
+// [out] heigt: height of the terrain
+// [out] return value: 0 if read in successfully 1 otherwise
+{
+	FILE *file=fopen(filename, "rb");
+	if(!file)
+		return -1;
+
+	OCTET octet;
+	QUARTET quartet;
+	QUARTET quartet_marker;
+	DUET duet;
+
+	fread(octet, 8, 1, file);
+	if(memcmp(octet, "TERRAGEN", 8))
+		return -1;
+
+	fread(octet, 8, 1, file);
+	if(memcmp(octet, "TERRAIN ", 8))
+		return -1;
+
+	fread(quartet, 4, 1, file);
+	if(memcmp(quartet, "SIZE", 4))
+		return -1;
+	fread(duet, 2, 1, file);
+	fseek(file, 2, SEEK_CUR);
+	int size=DUET_TO_NUMBER(duet);
+
+	int xpts=0, ypts=0;
+	do
+	{
+		fread(quartet_marker, 4, 1, file);
+
+		if(memcmp(quartet_marker, "XPTS", 4)==0)
+		{
+			fread(duet, 2, 1, file);
+			fseek(file, 2, SEEK_CUR);
+			xpts=DUET_TO_NUMBER(duet);
+			continue;
+		}
+
+		if(memcmp(quartet_marker, "YPTS", 4)==0)
+		{
+			fread(duet, 2, 1, file);
+			fseek(file, 2, SEEK_CUR);
+			ypts=DUET_TO_NUMBER(duet);
+			continue;
+		}
+
+		// I'm going to ignore the other segments so long
+		// so we can leave the quartet marker test to the
+		// while condition
+		//if(strcmp(quartet_marker, "SIZE")) // Ignore SIZE
+		//	fseek(file, 4, SEEK_CUR);
+
+		if(memcmp(quartet_marker, "SCAL", 4)==0&&scale) // Ignore SCAL
+		{
+			float fscale[3];
+			fread(&(fscale[0]), 4, 1, file);
+			fread(&(fscale[1]), 4, 1, file);
+			fread(&(fscale[2]), 4, 1, file);
+			scale[0]=fscale[0];
+			scale[1]=fscale[1];
+			scale[2]=fscale[2];
+		}
+
+		//if(strcmp(quartet_marker, "CRAD")) // Ignore CRAD
+		//	fseek(file, 4, SEEK_CUR);
+
+		//if(strcmp(quartet_marker, "CRVM")) // Ignore CRVM
+		//	fseek(file, 4, SEEK_CUR);
+
+	}while(memcmp(quartet_marker, "ALTW", 4));
+
+	int16_t height_scale, base_height;
+	fread(duet, 2, 1, file);
+	height_scale = DUET_TO_NUMBER(duet);
+	fread(duet, 2, 1, file);
+	base_height = DUET_TO_NUMBER(duet);
+
+	if(xpts==0&&ypts==0)
+	{
+		xpts=size+1;
+		ypts=size+1;
+	}
+
+	*width=xpts;
+	*height=ypts;
+
+	// The caller of this function is responsible
+	// to free the memory consumed by buffer
+	DUET *buffer=new DUET[xpts*ypts];
+	fread(buffer, 2, xpts*ypts, file);
+
+	*pbuffer=new double[xpts*ypts];
+	for(int y=0; y<ypts; y++)
+	{
+		for(int x=0; x<xpts; x++)
+		{
+			int16_t elev = (int16_t)DUET_TO_NUMBER( buffer[y*xpts+x] );
+			//memcpy(&elev, (buffer+(y*xpts+x)), 2);
+			(*pbuffer)[y*xpts+x]=
+				static_cast<double>(base_height+elev*height_scale/65536);
+		}
+	}
+	delete[] buffer;
+
+	// a last test, the next we read should be "EOF ", since currently the Terragen
+	// file format says, that "ALTW" must be the last segment of a file
+	// however it's no problem for _us_ if we've no "EOF " here, because it doesn't matter
+	fread(quartet, 4, 1, file);
+	if(memcmp(quartet, "EOF ", 4))
+		printf("read terrain file with \"EOF \" at the end\n");
+
+	fclose(file);
+	return 0;
+}
-- 
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