heightmap opengl

terrain_generator.c

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>

#include <GL/gl.h>
#include <GL/glu.h>

#include <SDL/SDL.h>

#define min(a,b) ((a < b) ? a : b)

int main(int argc, char *argv)
{
	SDL_Init(SDL_INIT_VIDEO);
	SDL_WM_SetCaption("OpenGL landscape", NULL);
	SDL_SetVideoMode(800, 450, 32, SDL_OPENGL);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(56, 800.0 / 450.0, 1, 1000);
	glEnable(GL_DEPTH_TEST);
	glClearColor(1, 1, 1, 1);
	srand(time(NULL));

	int loop = 1;
	SDL_Event event;

	int precision = 9, i, x, y, j, dx, dy, mx, my;
	long size = 1 << precision;
	float persistence = 0.5;

	unsigned char *map, *tmpmap;
	map = (unsigned char *) malloc(sizeof(unsigned char) * size * size);
	tmpmap = (unsigned char *) malloc(sizeof(unsigned char) * (size + 1) * (size + 1));

	for(i = 0; i < size * size; i++) map[i] = 0;

	for(i = 2; i <= precision; i++)
	{
		int lprec = 1 << i;
		int lsize = size / lprec;

		for(x = 0; x < size + 1; x += lsize) for(y = 0; y < size + 1; y += lsize)
		{
			tmpmap[x + y * (size + 1)] = rand() % 256;
		}

		for(x = 0; x < size; x++) for(y = 0; y < size; y++)
		{
			dx = x % lsize; dy = y % lsize;

			float a, b, c, d, ab, cd, abcd;

			if(dx != 0 || dy != 0) {
				mx = x - dx; my = y - dy;

				a = tmpmap[mx + my * (size + 1)] * 1.0;
				b = tmpmap[mx + lsize + my * (size + 1)] * 1.0;
				c = tmpmap[mx + (my + lsize) * (size + 1)] * 1.0;
				d = tmpmap[mx + lsize + (my + lsize) * (size + 1)] * 1.0;
	
				ab = a + ((float) dx / (float) lsize) * (b - a);
				cd = c + ((float) dx / (float) lsize) * (d - c);
				abcd = ab + ((float) dy / (float) lsize) * (cd - ab);

				tmpmap[x + y * (size + 1)] = floor(abcd);
			}
			
			map[x + y * size] = min(255, map[x + y * size] + (int) (floor((float) (tmpmap[x + y * (size + 1)]) * pow(0.5, i - 1))));
		}
	}

	printf("Heightmap generated\n");
	free(tmpmap);

	gluLookAt(5, 100, 5, size, 25, size, 0, 1, 0); 

	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();

	glBegin(GL_TRIANGLES);

	glColor3ub(127, 127, 127);

	for(x = 0; x < size - 1; x++) for(y = 0; y < size - 1; y++)
	{
			
		float a, b, c, d, co;
		a = map[x + y * size];
		b = map[x + 1 + y * size];
		c = map[x + (y + 1) * size];
		d = map[x + 1 + (y + 1) * size];

		a /=  2;
		b /= 2;
		c /= 2;
		d /= 2;
		co = x + y;
		co /= 2 * size;
		co *= 255;
		glColor3ub(floor(co), floor(co), floor(co));
		glVertex3d(x, a, y);
		glVertex3d(x + 1, b, y);
		glVertex3d(x, c, y + 1);

		glVertex3d(x + 1, b, y);
		glVertex3d(x, c, y + 1);
		glVertex3d(x + 1, d, y + 1);

	}
		
	glEnd();
	SDL_GL_SwapBuffers();



	while(loop)
	{
		SDL_WaitEvent(&event);
		switch(event.type)
		{
			case SDL_QUIT:
				loop = 0;
				exit(0);
				break;
		}

	}
	glDeleteShader(shader);
	shader = 0;

	SDL_Quit();

	free(map);
	free(src);

	return 0;
}