raycast.py

import os
import sys
import math
import random
import itertools
import pygame as pg

from collections import namedtuple


if sys.version_info[0] == 2:
    range = xrange


CAPTION = "Ray-Casting with Python"
SCREEN_SIZE = (1200, 600)
CIRCLE = 2*math.pi
SCALE = (SCREEN_SIZE[0]+SCREEN_SIZE[1])/1200.0
FIELD_OF_VIEW = math.pi*0.4
NO_WALL = float("inf")
RAIN_COLOR = (255, 255, 255, 40)


# Semantically meaningful tuples for use in GameMap and Camera class.
RayInfo = namedtuple("RayInfo", ["sin", "cos"])
WallInfo = namedtuple("WallInfo", ["top", "height"])


class Image(object):
    """A very basic class that couples an image with its dimensions"""
    def __init__(self, image):
        """
        The image argument is a preloaded and converted pg.Surface object.
        """
        self.image = image
        self.width, self.height = self.image.get_size()


class Player(object):
    """Handles the player's position, rotation, and control."""
    def __init__(self, x, y, direction):
        """
        The arguments x and y are floating points.  Anything between zero
        and the game map size is on our generated map.
        Choosing a point outside this range ensures our player doesn't spawn
        inside a wall.  The direction argument is the initial angle (given in
        radians) of the player.
        """
        self.x = x
        self.y = y
        self.direction = direction
        self.speed = 3 # Map cells per second.
        self.rotate_speed = CIRCLE/2  # 180 degrees in a second.
        self.weapon = Image(IMAGES["knife"])
        self.paces = 0 # Used for weapon placement.

    def rotate(self, angle):
        """Change the player's direction when appropriate key is pressed."""
        self.direction = (self.direction+angle+CIRCLE)%CIRCLE

    def walk(self, distance, game_map):
        """
        Calculate the player's next position, and move if he will
        not end up inside a wall.
        """
        dx = math.cos(self.direction)*distance
        dy = math.sin(self.direction)*distance
        if game_map.get(self.x+dx, self.y) <= 0:
            self.x += dx
        if game_map.get(self.x, self.y+dy) <= 0:
            self.y += dy
        self.paces += distance

    def update(self, keys, dt, game_map):
        """Execute movement functions if the appropriate key is pressed."""
        if keys[pg.K_LEFT]:
            self.rotate(-self.rotate_speed*dt)
        if keys[pg.K_RIGHT]:
            self.rotate(self.rotate_speed*dt)
        if keys[pg.K_UP]:
            self.walk(self.speed*dt, game_map)
        if keys[pg.K_DOWN]:
            self.walk(-self.speed*dt, game_map)


class GameMap(object):
    """
    A class to generate a random map for us; handle ray casting;
    and provide a method of detecting colissions.
    """
    def __init__(self, size):
        """
        The size argument is an integer which tells us the width and height
        of our game grid.  For example, a size of 32 will create a 32x32 map.
        """
        self.size = size
        self.wall_grid = self.randomize()
        self.sky_box = Image(IMAGES["sky"])
        self.wall_texture = Image(IMAGES["texture"])
        self.light = 0

    def get(self, x, y):
        """A method to check if a given coordinate is colliding with a wall."""
        point = (int(math.floor(x)), int(math.floor(y)))
        return self.wall_grid.get(point, -1)

    def randomize(self):
        """
        Generate our map randomly.  In the code below their is a 30% chance
        of a cell containing a wall.
        """
        coordinates = itertools.product(range(self.size), repeat=2)
        return {coord : random.random()<0.3 for coord in coordinates}

    def cast_ray(self, point, angle, cast_range):
        """
        The meat of our ray casting program.  Given a point,
        an angle (in radians), and a maximum cast range, check if any
        collisions with the ray occur.  Casting will stop if a collision is
        detected (cell with greater than 0 height), or our maximum casting
        range is exceeded without detecting anything.
        """
        info = RayInfo(math.sin(angle), math.cos(angle))
        origin = Point(point)
        ray = [origin]
        while origin.height <= 0 and origin.distance <= cast_range:
            dist = origin.distance
            step_x = origin.step(info.sin, info.cos)
            step_y = origin.step(info.cos, info.sin, invert=True)
            if step_x.length < step_y.length:
                next_step = step_x.inspect(info, self, 1, 0, dist, step_x.y)
            else:
                next_step = step_y.inspect(info, self, 0, 1, dist, step_y.x)
            ray.append(next_step)
            origin = next_step
        return ray

    def update(self, dt):
        """Adjust ambient lighting based on time."""
        if self.light > 0:
            self.light = max(self.light-10*dt, 0)
        elif random.random()*5 < dt:
            self.light = 2


class Point(object):
    """
    A fairly basic class to assist us with ray casting.  The return value of
    the GameMap.cast_ray() method is a list of Point instances.
    """
    def __init__(self, point, length=None):
        self.x = point[0]
        self.y = point[1]
        self.height = 0
        self.distance = 0
        self.shading = None
        self.length = length

    def step(self, rise, run, invert=False):
        """
        Return a new Point advanced one step from the caller.  If run is
        zero, the length of the new Point will be infinite.
        """
        try:
            x, y = (self.y,self.x) if invert else (self.x,self.y)
            dx = math.floor(x+1)-x if run > 0 else math.ceil(x-1)-x
            dy = dx*(rise/run)
            next_x = y+dy if invert else x+dx
            next_y = x+dx if invert else y+dy
            length = math.hypot(dx, dy)
        except ZeroDivisionError:
            next_x = next_y = None
            length = NO_WALL
        return Point((next_x,next_y), length)

    def inspect(self, info, game_map, shift_x, shift_y, distance, offset):
        """
        Ran when the step is selected as the next in the ray.
        Sets the steps self.height, self.distance, and self.shading,
        to the required values.
        """
        dx = shift_x if info.cos<0 else 0
        dy = shift_y if info.sin<0 else 0
        self.height = game_map.get(self.x-dx, self.y-dy)
        self.distance = distance+self.length
        if shift_x:
            self.shading = 2 if info.cos<0 else 0
        else:
            self.shading = 2 if info.sin<0 else 1
        self.offset = offset-math.floor(offset)
        return self


class Camera(object):
    """Handles the projection and rendering of all objects on the screen."""
    def __init__(self, screen, resolution):
        self.screen = screen
        self.width, self.height = self.screen.get_size()
        self.resolution = float(resolution)
        self.spacing = self.width/resolution
        self.field_of_view = FIELD_OF_VIEW
        self.range = 8
        self.light_range = 5
        self.scale = SCALE
        self.flash = pg.Surface((self.width, self.height//2)).convert_alpha()

    def render(self, player, game_map):
        """Render everything in order."""
        self.draw_sky(player.direction, game_map.sky_box, game_map.light)
        self.draw_columns(player, game_map)
        self.draw_weapon(player.weapon, player.paces)

    def draw_sky(self, direction, sky, ambient_light):
        """
        Calculate the skies offset so that it wraps, and draw.
        If the ambient light is greater than zero, draw lightning flash.
        """
        left = -sky.width*direction/CIRCLE
        self.screen.blit(sky.image, (left,0))
        if left<sky.width-self.width:
            self.screen.blit(sky.image, (left+sky.width,0))
        if ambient_light > 0:
            alpha = 255*min(1, ambient_light*0.1)
            self.flash.fill((255,255,255,alpha))
            self.screen.blit(self.flash, (0, self.height//2))

    def draw_columns(self, player, game_map):
        """
        For every column in the given resolution, cast a ray, and render that
        column.
        """
        for column in range(int(self.resolution)):
            angle = self.field_of_view*(column/self.resolution-0.5)
            point = player.x, player.y
            ray = game_map.cast_ray(point, player.direction+angle, self.range)
            self.draw_column(column, ray, angle, game_map)

    def draw_column(self, column, ray, angle, game_map):
        """
        Examine each step of the ray, starting with the furthest.
        If the height is greater than zero, render the column (and shadow).
        Rain drops will be drawn for every step.
        """
        left = int(math.floor(column*self.spacing))
        for ray_index in range(len(ray)-1, -1, -1):
            step = ray[ray_index]
            if step.height > 0:
                texture = game_map.wall_texture
                width = int(math.ceil(self.spacing))
                texture_x = int(texture.width*step.offset) ###
                wall = self.project(step.height, angle, step.distance)
                image_location = pg.Rect(texture_x, 0, 1, texture.height)
                image_slice = texture.image.subsurface(image_location)
                scale_rect = pg.Rect(left, wall.top, width, wall.height)
                scaled = pg.transform.scale(image_slice, scale_rect.size)
                self.screen.blit(scaled, scale_rect)
                self.draw_shadow(step, scale_rect, game_map.light)
            self.draw_rain(step, angle, left, ray_index)

    def draw_shadow(self, step, scale_rect, light):
        """
        Render the shadow on a column with regards to its distance and
        shading attribute.
        """
        shade_value = step.distance+step.shading
        max_light = shade_value/float(self.light_range)-light
        alpha = 255*min(1, max(max_light, 0))
        shade_slice = pg.Surface(scale_rect.size).convert_alpha()
        shade_slice.fill((0,0,0,alpha))
        self.screen.blit(shade_slice, scale_rect)

    def draw_rain(self, step, angle, left, ray_index):
        """
        Render a number of rain drops to add depth to our scene and mask
        roughness.
        """
        rain_drops = int(random.random()**3*ray_index)
        if rain_drops:
            rain = self.project(0.1, angle, step.distance)
            drop = pg.Surface((1,rain.height)).convert_alpha()
            drop.fill(RAIN_COLOR)
        for _ in range(rain_drops):
            self.screen.blit(drop, (left, random.random()*rain.top))

    def draw_weapon(self, weapon, paces):
        """
        Calulate new weapon position based on player's pace attribute,
        and render.
        """
        bob_x = math.cos(paces*2)*self.scale*6
        bob_y = math.sin(paces*4)*self.scale*6
        left = self.width*0.66+bob_x
        top = self.height*0.6+bob_y
        self.screen.blit(weapon.image, (left, top))

    def project(self, height, angle, distance):
        """
        Find the position on the screen after perspective projection.
        A minimum value is used for z to prevent slices blowing up to
        unmanageable sizes when the player is very close.
        """
        z = max(distance*math.cos(angle),0.2)
        wall_height = self.height*height/float(z)
        bottom = self.height/float(2)*(1+1/float(z))
        return WallInfo(bottom-wall_height, int(wall_height))


class Control(object):
    """
    The core of our program.  Responsible for running our main loop;
    processing events; updating; and rendering.
    """
    def __init__(self):
        self.screen = pg.display.get_surface()
        self.clock = pg.time.Clock()
        self.fps = 60.0
        self.keys = pg.key.get_pressed()
        self.done = False
        self.player = Player(15.3, -1.2, math.pi*0.3)
        self.game_map = GameMap(32)
        self.camera = Camera(self.screen, 300)

    def event_loop(self):
        """
        Quit game on a quit event and update self.keys on any keyup or keydown.
        """
        for event in pg.event.get():
            if event.type == pg.QUIT:
                self.done = True
            elif event.type in (pg.KEYDOWN, pg.KEYUP):
                self.keys = pg.key.get_pressed()

    def update(self, dt):
        """Update the game_map and player."""
        self.game_map.update(dt)
        self.player.update(self.keys, dt, self.game_map)

    def display_fps(self):
        """Show the program's FPS in the window handle."""
        caption = "{} - FPS: {:.2f}".format(CAPTION, self.clock.get_fps())
        pg.display.set_caption(caption)

    def main_loop(self):
        """Process events, update, and render."""
        dt = self.clock.tick(self.fps)/1000.0
        while not self.done:
            self.event_loop()
            self.update(dt)
            self.camera.render(self.player, self.game_map)
            dt = self.clock.tick(self.fps)/1000.0
            pg.display.update()
            self.display_fps()


def load_resources():
    """
    Return a dictionary of our needed images; loaded, converted, and scaled.
    """
    images = {}
    knife_image = pg.image.load("knife_hand.png").convert_alpha()
    knife_w, knife_h = knife_image.get_size()
    knife_scale = (int(knife_w*SCALE), int(knife_h*SCALE))
    images["knife"] = pg.transform.smoothscale(knife_image, knife_scale)
    images["texture"] = pg.image.load("wall_texture.jpg").convert()
    sky_size = int(SCREEN_SIZE[0]*(CIRCLE/FIELD_OF_VIEW)), SCREEN_SIZE[1]
    sky_box_image = pg.image.load("deathvalley_panorama.jpg").convert()
    images["sky"] = pg.transform.smoothscale(sky_box_image, sky_size)
    return images


def main():
    """Prepare the display, load images, and get our programming running."""
    global IMAGES
    os.environ["SDL_VIDEO_CENTERED"] = "True"
    pg.init()
    pg.display.set_mode(SCREEN_SIZE)
    IMAGES = load_resources()
    Control().main_loop()
    pg.quit()
    sys.exit()


if __name__ == "__main__":
    main()