path: root/simple-raycaster/src/main.c

#include <GL/glew.h> // must come before glfw3
#include <GLFW/glfw3.h>
#include <stdio.h>
#include <math.h>

#include "player.h"

// TODO: move to implicit map definition with level editor in future
#define MAP_HEIGHT 20
#define MAP_WIDTH 10
int world_map[MAP_HEIGHT][MAP_WIDTH] = {
    {1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
    {1, 0, 0, 0, 0, 0, 0, 0, 0, 1},
    {1, 0, 2, 2, 2, 0, 0, 0, 0, 1},
    {1, 0, 2, 2, 2, 0, 0, 0, 0, 1},
    {1, 0, 2, 2, 2, 0, 0, 0, 0, 1},
    {1, 0, 2, 2, 2, 0, 0, 0, 0, 1},
    {1, 0, 2, 2, 2, 0, 4, 4, 0, 1},
    {1, 0, 0, 0, 0, 0, 4, 4, 0, 1},
    {1, 0, 0, 0, 0, 0, 4, 4, 0, 1},
    {1, 0, 0, 0, 0, 0, 4, 4, 0, 1},
    {1, 0, 0, 0, 0, 0, 4, 4, 0, 1},
    {1, 0, 0, 0, 0, 0, 4, 4, 0, 1},
    {1, 0, 0, 0, 0, 0, 4, 4, 0, 1},
    {1, 0, 3, 3, 3, 0, 4, 4, 0, 1},
    {1, 0, 3, 3, 3, 0, 0, 0, 0, 1},
    {1, 0, 3, 3, 3, 0, 0, 0, 0, 1},
    {1, 0, 3, 3, 3, 0, 0, 0, 0, 1},
    {1, 0, 3, 3, 3, 0, 0, 0, 0, 1},
    {1, 0, 0, 0, 0, 0, 0, 0, 0, 1},
    {1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
};

typedef struct {
	unsigned char r, g, b;
} ColorRGB;

// honest- this function can from chatgpt- cross-reference this with other raycasting guides
void raycast(Player *player, GLubyte *pixels, int width, int height) {
    	int screen_width = width;
    	int screen_height = height;

    	for (int x = 0; x < screen_width; ++x) {
        	// Calculate ray position and direction
        	double camera_x = 2.0 * x / (double)screen_width - 1; // x-coordinate in camera space
        	double ray_dir_x = player->dir_x + player->plane_x * camera_x;
        	double ray_dir_y = player->dir_y + player->plane_y * camera_x;

        	// Which box of the map we're in
        	int map_x = (int)player->pos_x;
        	int map_y = (int)player->pos_y;

        	// Length of ray from one x or y-side to next x or y-side
        	double delta_dist_x = fabs(1 / ray_dir_x);
        	double delta_dist_y = fabs(1 / ray_dir_y);

        	// Length of ray from current position to next x or y-side
        	double side_dist_x;
        	double side_dist_y;

        	// Direction to step in x or y-direction (either +1 or -1)
        	int step_x;
        	int step_y;

        	// Was a wall hit?
        	int hit = 0;
        	// Was the wall hit a wall facing north, east-west, or south?
        	int side;
        	if (ray_dir_x < 0) {
            		step_x = -1;
            		side_dist_x = (player->pos_x - map_x) * delta_dist_x;
        	} else {
            		step_x = 1;
            		side_dist_x = (map_x + 1.0 - player->pos_x) * delta_dist_x;
        	}
        	if (ray_dir_y < 0) {
            		step_y = -1;
            		side_dist_y = (player->pos_y - map_y) * delta_dist_y;
        	} else {
            		step_y = 1;
            		side_dist_y = (map_y + 1.0 - player->pos_y) * delta_dist_y;
        	}

        	// Perform DDA
        	while (hit == 0) {
            		// Jump to next map square
            		if (side_dist_x < side_dist_y) {
                		side_dist_x += delta_dist_x;
                		map_x += step_x;
                		side = (ray_dir_x > 0) ? 0 : 2;
            		} else {
                		side_dist_y += delta_dist_y;
                		map_y += step_y;
                		side = 1;
            		}
            		// Check if ray has hit a wall
            		if (world_map[map_x][map_y] > 0) { hit = 1; }
        	}

		// calculate distance projected on camera direction
		double perp_wall_dist;
		if (side == 0 || side == 2) { perp_wall_dist = (map_x - player->pos_x + (1 - step_x) / 2) / ray_dir_x; }
		else           { perp_wall_dist = (map_y - player->pos_y + (1 - step_y) / 2) / ray_dir_y; }

		// fog effect
		float fog_distance = 15.0f;
		float scale_factor = 1.0f - perp_wall_dist / fog_distance;
		if (scale_factor < 0.0f) { scale_factor = 0.0f; }
		
		// calculate height of line on screen
		int line_height = (int)(screen_height / perp_wall_dist);
		//int draw_start = -line_height / 2 + screen_height / 2;
		//if (draw_start < 0) { draw_start = 0; }
		//int draw_end = line_height / 2 + screen_height / 2;
		//if (draw_end >= screen_height)  { draw_end = screen_height - 1; }
		int pitch = screen_height / 2 * player->look_angle;
		int start_y = -line_height / 2 + screen_height / 2 + pitch;
		if (start_y < 0) { start_y = 0; }
		int end_y = line_height / 2 + screen_height / 2 + pitch;
		if (end_y >= screen_height) { end_y = screen_height - 1; }


		// colors :)
		ColorRGB color;
		if (world_map[map_x][map_y] == 1)	color = (ColorRGB){.r = 255, .g = 255, .b = 255};
		else if (world_map[map_x][map_y] == 2)	color = (ColorRGB){.r = 255, .g = 0, .b = 0};
		else if (world_map[map_x][map_y] == 3)	color = (ColorRGB){.r = 0, .g = 255, .b = 0};
		else if (world_map[map_x][map_y] == 4)	color = (ColorRGB){.r = 0, .g = 0, .b = 255};
		else					color = (ColorRGB){.r = 0, .g = 0, .b = 0};

		if (side == 1) {
			color.r /= 2;
			color.g /= 2;
			color.b /= 2;
		} else if (side == 2) {
			color.r /= 4;
			color.g /= 4;
			color.b /= 4;
		}

		// scale brightness in accordance with distance (for fog)
		color.r *= scale_factor;
		color.g *= scale_factor;
		color.b *= scale_factor;

		int index;
		for (int y = 0; y < screen_height; y++) {
			index = y * screen_width * 3 + x * 3;
			if (y >= start_y && y <= end_y) {
				// draw something
				pixels[index] = color.r;
				pixels[index+1] = color.g;
				pixels[index+2] = color.b;
			} else {
				// fill blank space
				pixels[index] = 0;	
				pixels[index+1] = 0;	
				pixels[index+2] = 0;	
			}
		}

    	}
}

int main(int argc, char *argv[]) {
	GLFWwindow* window;

	double mouse_x;
	double mouse_y;

	// init player
	Player player;
	player.pos_y = 2.0f;
	player.pos_x = 9.0f;
	player.dir_x = 1.0f;
	player.dir_y = 0.0f;
	player.plane_x = 0.20f; // FOV related
	player.plane_y = 0.90f; // FOV related
	player.look_angle = 0.0f;
	player.move_speed = 0.035f;
	player.sensitivity = 0.001f;

	// initiate glfw library
	if (!glfwInit()){
		printf("Failed to initiate GLFW.\n");
		return -1;
	}

	// create glfw window
	GLFWmonitor* primary = glfwGetPrimaryMonitor();
	const GLFWvidmode* mode = glfwGetVideoMode(primary);
	//window = glfwCreateWindow(800, 600, "raycaster", NULL, NULL);
	window = glfwCreateWindow(mode->width, mode->height, "raycaster", primary, NULL);
	if (!window){
		printf("Failed to create GLFW window.\n");
		glfwTerminate();
		return -1;
	}

	// make window current
	glfwMakeContextCurrent(window);
	glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);

	// update mouse position
	// glfwGetCursorPos(window, &mouse_x, &mouse_y);
	mouse_x -= mode->width / 2;
	mouse_y -= mode->height / 2;

	// setup orthographic projection camera
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glOrtho(0.0, mode->width, mode->height, 0.0, -1.0, 1.0);
	glMatrixMode(GL_MODELVIEW);

	// TODO: move timers into a header
	double last_time = glfwGetTime();
	int nb_frames = 0;
	// TODO: render FPS with freetype or something as opposed to updating title
	char title[200];

	// setup pbo for optimized performance
	if (glewInit() != GLEW_OK) { 
		printf("Failed to initiate GLEW.\n");
		return -1;
	}
	GLuint pbo = 0;

	glGenBuffers(1, &pbo);
	glBindBuffer(GL_PIXEL_UNPACK_BUFFER, pbo);
	glBufferData(GL_PIXEL_UNPACK_BUFFER, mode->width * mode->height * 3, 0, GL_STREAM_DRAW);

	int index = 0;
	glViewport(0, 0, mode->width, mode->height);
	while (!glfwWindowShouldClose(window)) {

		// Stop loop if window isn't focused
		if(!glfwGetWindowAttrib(window, GLFW_FOCUSED)){
			continue;
		}

		// timing section
		double current_time = glfwGetTime();
		nb_frames++;
		if (current_time - last_time >= 1.0) {
			sprintf(title, "FPS: %d", nb_frames);
			glfwSetWindowTitle(window, title);
			nb_frames = 0;
			last_time += 1.0;
		}


		// clear window
		glClear(GL_COLOR_BUFFER_BIT);
		glLoadIdentity();

		// main raycast function
        float prev_position[2] = {player.pos_x, player.pos_y};
		move_player(&player, window, &mouse_x, &mouse_y, mode->width, mode->height);
        if (world_map[(int)player.pos_x][(int)player.pos_y] != 0) {
            player.pos_x = prev_position[0];
            player.pos_y = prev_position[1];
        }
		GLubyte* pixels = (GLubyte*)glMapBuffer(GL_PIXEL_UNPACK_BUFFER, GL_WRITE_ONLY);
		raycast(&player, pixels, mode->width, mode->height);

		// pbo
		glUnmapBuffer(GL_PIXEL_UNPACK_BUFFER);
		glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
		glPixelStorei(GL_UNPACK_ROW_LENGTH, mode->width);
		glWindowPos2i(0, 0);
		glDrawPixels(mode->width, mode->height, GL_RGB, GL_UNSIGNED_BYTE, 0);

		
		glfwSwapBuffers(window);
		glfwPollEvents();

	}

	printf("Terminating GLFW...\n");
	glfwTerminate();
	printf("Clearing buffer...\n");
	glDeleteBuffers(1, &pbo);
	return 0;

}