From 181aa007edec1c59b29a548d57e0ae2646fbc551 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Georges=20Dup=C3=A9ron?= <jahvascriptmaniac+github@free.fr>
Date: Wed, 21 Sep 2011 15:54:33 +0200
Subject: [PATCH] =?UTF-8?q?Ajout=20de=20mon=20g=C3=A9n=C3=A9rateur=20de=20?=
 =?UTF-8?q?terrain=20(gd).?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .gitignore       |   1 +
 Makefile         |   5 ++
 README.markdown  |  10 ++++
 simple-terrain.c | 120 +++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 136 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Makefile
 create mode 100644 README.markdown
 create mode 100644 simple-terrain.c

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..a200f5e
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+simple-terrain
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..712b688
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,5 @@
+all: simple-terrain
+	./simple-terrain | display
+
+simple-terrain: simple-terrain.c
+	gcc simple-terrain.c -o simple-terrain
diff --git a/README.markdown b/README.markdown
new file mode 100644
index 0000000..fad719c
--- /dev/null
+++ b/README.markdown
@@ -0,0 +1,10 @@
+Minimal requirements
+====================
+
+* imagemagick
+* gcc
+
+How to test this program ?
+==========================
+
+    make
diff --git a/simple-terrain.c b/simple-terrain.c
new file mode 100644
index 0000000..7c6c786
--- /dev/null
+++ b/simple-terrain.c
@@ -0,0 +1,120 @@
+#include <stdio.h>
+#include <math.h>
+
+#define SIZE 1024
+// best value for MAX_DETAIL is 8
+#define MAX_DETAIL 8
+
+int bsr(int x) {
+	asm volatile("bsr %0, %0" : "=r" (x) : "0" (x) : "0");
+	return x;
+}
+
+int random_from_rec2(int a, int b, int c) {
+	b += a; // b = a + b                           // 2 bytes
+	a *= b; // a = a * (a + b)                     // 2 bytes
+	b ^= a; // b = (a + b) ^ (a * (a + b))         // 2 bytes
+	a += 211; // a = (a * (a + b)) + 5             // 2-3 bytes ; 211 is wonderfull.
+	b /= 2; // b = ((a + b) ^ (a * (a + b))) / 2   // 2 bytes
+	
+	if (c == 0)
+//		return a >> 2;                             // 3 bytes :( , but we can do with >>1 or even without.
+		return a >> 1;
+	return random_from_rec2(a, b, c-1);
+}
+
+unsigned char random_from(int a, int b) {
+	return (random_from_rec2(a, b, 1)) & 0xff;
+}
+
+/*	Alternate method to compute a single detail level for z.
+	// This square
+	z = random_from(xd, yd);
+	
+	// x interpolation
+	zb = random_from(xd + 1, yd);
+	z += ((zb-z) * (x & mask)) >> detail;
+	
+	// y interpolation
+	zc = random_from(xd, yd + 1);
+	zb = random_from(xd + 1, yd + 1);
+	zc += ((zb-zc) * (x & mask)) >> detail;
+	z  += ((zc-z)  * (y & mask)) >> detail;
+*/
+				
+int get_z(int x, int y) {
+	int detail, mask;
+	int xd, yd;
+	int z00, z01, z10, z11;
+	int xm, ym, mxm, mym;
+	unsigned int z, ztot;
+	
+	ztot = 0;
+	for (detail = 0; detail < MAX_DETAIL; detail++) {
+		x++; // slightly blurs vertical
+		y++; // and horizontal artifacts.
+		
+		mask = (1<<detail) - 1;
+		xd   = x >> detail;
+		yd   = y >> detail;
+		
+		if (0 == 0) {
+		// Method one
+			z00 = random_from(xd + 0, yd + 0);
+			z01 = random_from(xd + 0, yd + 1);
+			z10 = random_from(xd + 1, yd + 0);
+			z11 = random_from(xd + 1, yd + 1);
+			
+			xm = ((xd + 1) << detail) - x;
+			ym = ((yd + 1) << detail) - y;
+			mxm = (1 << detail) - xm;
+			mym = (1 << detail) - ym;
+			
+			z = 0;
+			z += z00 * xm  * ym ;
+			z += z01 * xm  * mym;
+			z += z10 * mxm * ym ;
+			z += z11 * mxm * mym;
+			
+			z >>= ((detail * 2) + (MAX_DETAIL - detail));
+		// Method two
+		} else {		
+		// Alternate method
+			int zb, zc;
+			// This square
+			z = random_from(xd, yd);
+			
+			// x interpolation
+			zb = random_from(xd, yd + 1);
+			z += ((zb-z) * (y & mask)) >> detail;
+			
+			// y interpolation
+			zc = random_from(xd + 1, yd);
+			zb = random_from(xd + 1, yd + 1);
+			zc += ((zb-zc) * (y & mask)) >> detail;
+			z  += ((zc-z)  * (x & mask)) >> detail;
+			
+			z >>= 0;
+		// Alternate method
+		}
+		
+		// add this detail level
+		ztot += z;
+	}
+	//x = x - MAX_DETAIL; // when using x++ and y++
+	//y = y - MAX_DETAIL; // to reduce artifacts.
+	
+	return ztot & 0xff;
+}
+
+int main(int argc, char** argv) {
+	int y;
+	int x;
+	fprintf(stderr, "Aide :\n");
+	fprintf(stderr, "Utilisez ./simple-terrain | display pour visualiser la sortie.\n");
+	fprintf(stderr, "Utilisez ./simple-terrain > fichier.pnm pour sauvegarder.\n");
+        printf("P5 %d %d 255\n", SIZE, SIZE);
+        for (y=SIZE-1; y>=0; y--)
+                for (x=0; x<SIZE; x++)
+			printf("%c", (char)get_z(x,y));
+}