first commit

main.c

+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <time.h>
+#include <string.h>
+#include "qdbmp.h"
+
+typedef struct RigidMass
+{
+	long mass;
+	double vx, vy;
+	double x, y;
+	double dvx, dvy;
+	double tick_time;
+	
+} RigidMass_t;
+
+double G = 6.67408E-11;
+
+//Calculates delta V on body, due to other.
+void calcGravity(RigidMass_t *body, RigidMass_t other)
+{
+	double dx = body->x - other.x;
+	double dy = body->y - other.y;
+	double dist_squared = dx * dx + dy * dy;
+
+	double v = -G * other.mass / dist_squared * body->tick_time;
+
+	double hyp = sqrt(dist_squared);
+	body->dvx += v * (dx) / hyp;
+	body->dvy += v * (dy) / hyp;
+}
+
+void processTick(RigidMass_t *body)
+{
+	//technically, we could just remove dvx/dvy
+	//and work with vx/vy directly, since they don't change anything other than when
+	//processing the tick here
+	body->vx += body->dvx;
+	body->vy += body->dvy;
+	body->dvx = 0;
+	body->dvy = 0;
+	body->x += body->vx * body->tick_time;
+	body->y += body->vy * body->tick_time;
+}
+
+//END PHYSICS ENGINE
+
+//thank you, stackoverflow
+/* reverse:  reverse string s in place */
+ void reverse(char s[])
+ {
+     int i, j;
+     char c;
+
+     for (i = 0, j = strlen(s)-1; i<j; i++, j--) {
+         c = s[i];
+         s[i] = s[j];
+         s[j] = c;
+     }
+}
+
+/* itoa:  convert n to characters in s */
+void itoa(int n, char s[])
+{
+	int i, sign;
+	
+	if ((sign = n) < 0)  /* record sign */
+		n = -n;          /* make n positive */
+	i = 0;
+	do {       /* generate digits in reverse order */
+		s[i++] = n % 10 + '0';   /* get next digit */
+	} while ((n /= 10) > 0);     /* delete it */
+	if (sign < 0)
+		s[i++] = '-';
+	s[i] = '\0';
+	reverse(s);
+}
+//END SO
+
+#define numStars 10000
+int w = 1000;
+int h = 1000;
+double max_component_vel = 3;
+
+RigidMass_t stars[numStars];
+void generateStars()
+{
+	RigidMass_t new;
+	new.mass = 500000000000;
+	new.dvx = 0;
+	new.dvy = 0;
+	new.tick_time = 0.05;
+		
+	for(int i = 0; i < numStars; i++)
+	{
+		new.x = rand() % 250 + 375; //375 to 625
+		new.y = rand() % 250 + 375;
+		double dx = new.x - w / 2;
+		double dy = new.y - h / 2;
+
+		if(abs(dx) <= abs(dy))
+		{
+			new.vx = (double)rand()/(double)(RAND_MAX/max_component_vel);
+			new.vy = -new.vx * dx / dy;
+		}
+		else
+		{
+			new.vy = (double)rand()/(double)(RAND_MAX/max_component_vel);
+			new.vx = -new.vy * dy / dx;
+		}
+
+		if(new.y < new.x)
+		{
+			new.vy = -new.vy;
+			new.vx = -new.vx;
+		}
+		
+		stars[i] = new;
+	}
+}
+
+void iterate()
+{
+	#pragma omp parallel for
+	for(int a = 0; a < numStars; a++)
+	{
+		for(int b = 0; b < numStars; b++)
+		{
+			if(abs(stars[a].x - stars[b].x) > 0.1 && abs(stars[a].y - stars[b].y) > 0.1)
+			{
+				//printf("%d, %d \r\n", stars[a].dvx, stars[a].dvy);
+				calcGravity(stars + a, stars[b]);
+			}
+		}
+	}
+
+	//'commit' the deltaV
+	for(int a = 0; a < numStars; a++)
+	{
+		processTick(stars + a);
+		//printf("%f, %f \r\n", stars[a].x, stars[a].y);
+	}
+}
+
+BMP *out;
+void addToImage()
+{
+	for(int a = 0; a < numStars; a++)
+	{
+		BMP_SetPixelRGB(out, stars[a].x, stars[a].y, 0, 150, 0);
+	}
+}
+
+void saveImage(double frame)
+{
+	char filename[50];
+	char buffer[46];
+	strcpy(filename, "img/");
+	itoa(frame, buffer);
+	strcat(filename, buffer);
+	strcat(filename, ".bmp");
+	
+	BMP_WriteFile(out, filename);
+
+	
+	BMP_Free(out);
+	out = BMP_Create(w, h, 24);
+}
+
+int main()
+{
+	srand(time(NULL));
+	out = BMP_Create(w, h, 24);
+
+	generateStars();
+	
+	for(int i = 0; i < 1000; i++)
+	{
+		iterate();
+		addToImage();
+		if (i % 10 == 0)
+		{
+			saveImage(i / 10);
+		}
+	}
+	
+	return 0;
+}

qdbmp.h

+#ifndef _BMP_H_
+#define _BMP_H_
+
+
+/**************************************************************
+
+	QDBMP - Quick n' Dirty BMP
+
+	v1.0.0 - 2007-04-07
+	http://qdbmp.sourceforge.net
+
+
+	The library supports the following BMP variants:
+	1. Uncompressed 32 BPP (alpha values are ignored)
+	2. Uncompressed 24 BPP
+	3. Uncompressed 8 BPP (indexed color)
+
+	QDBMP is free and open source software, distributed
+	under the MIT licence.
+
+	Copyright (c) 2007 Chai Braudo (braudo@users.sourceforge.net)
+
+	Permission is hereby granted, free of charge, to any person obtaining a copy
+	of this software and associated documentation files (the "Software"), to deal
+	in the Software without restriction, including without limitation the rights
+	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	copies of the Software, and to permit persons to whom the Software is
+	furnished to do so, subject to the following conditions:
+
+	The above copyright notice and this permission notice shall be included in
+	all copies or substantial portions of the Software.
+
+	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+	THE SOFTWARE.
+
+**************************************************************/
+
+#include <stdio.h>
+
+
+
+/* Type definitions */
+#ifndef UINT
+	#define UINT	unsigned long int
+#endif
+
+#ifndef USHORT
+	#define USHORT	unsigned short
+#endif
+
+#ifndef UCHAR
+	#define UCHAR	unsigned char
+#endif
+
+
+/* Version */
+#define QDBMP_VERSION_MAJOR		1
+#define QDBMP_VERSION_MINOR		0
+#define QDBMP_VERSION_PATCH		1
+
+
+/* Error codes */
+typedef enum
+{
+	BMP_OK = 0,				/* No error */
+	BMP_ERROR,				/* General error */
+	BMP_OUT_OF_MEMORY,		/* Could not allocate enough memory to complete the operation */
+	BMP_IO_ERROR,			/* General input/output error */
+	BMP_FILE_NOT_FOUND,		/* File not found */
+	BMP_FILE_NOT_SUPPORTED,	/* File is not a supported BMP variant */
+	BMP_FILE_INVALID,		/* File is not a BMP image or is an invalid BMP */
+	BMP_INVALID_ARGUMENT,	/* An argument is invalid or out of range */
+	BMP_TYPE_MISMATCH,		/* The requested action is not compatible with the BMP's type */
+	BMP_ERROR_NUM
+} BMP_STATUS;
+
+
+/* Bitmap image */
+typedef struct _BMP BMP;
+
+
+
+
+/*********************************** Public methods **********************************/
+
+
+/* Construction/destruction */
+BMP*			BMP_Create					( UINT width, UINT height, USHORT depth );
+void			BMP_Free					( BMP* bmp );
+
+
+/* I/O */
+BMP*			BMP_ReadFile				( const char* filename );
+void			BMP_WriteFile				( BMP* bmp, const char* filename );
+
+
+/* Meta info */
+UINT			BMP_GetWidth				( BMP* bmp );
+UINT			BMP_GetHeight				( BMP* bmp );
+USHORT			BMP_GetDepth				( BMP* bmp );
+
+
+/* Pixel access */
+void			BMP_GetPixelRGB				( BMP* bmp, UINT x, UINT y, UCHAR* r, UCHAR* g, UCHAR* b );
+void			BMP_SetPixelRGB				( BMP* bmp, UINT x, UINT y, UCHAR r, UCHAR g, UCHAR b );
+void			BMP_GetPixelIndex			( BMP* bmp, UINT x, UINT y, UCHAR* val );
+void			BMP_SetPixelIndex			( BMP* bmp, UINT x, UINT y, UCHAR val );
+
+
+/* Palette handling */
+void			BMP_GetPaletteColor			( BMP* bmp, UCHAR index, UCHAR* r, UCHAR* g, UCHAR* b );
+void			BMP_SetPaletteColor			( BMP* bmp, UCHAR index, UCHAR r, UCHAR g, UCHAR b );
+
+
+/* Error handling */
+BMP_STATUS		BMP_GetError				();
+const char*		BMP_GetErrorDescription		();
+
+
+/* Useful macro that may be used after each BMP operation to check for an error */
+#define BMP_CHECK_ERROR( output_file, return_value ) \
+	if ( BMP_GetError() != BMP_OK )													\
+	{																				\
+		fprintf( ( output_file ), "BMP error: %s\n", BMP_GetErrorDescription() );	\
+		return( return_value );														\
+	}																				\
+
+#endif