Pygame Rotated Shooting

Question

Me and a few friends have been coding an intresting new shooting mechanic. For It to work, we need to shoot in the direction the player is facing. The Sprite is being rotate

Answer 1

This example demonstrates how vectors can be utilized to control the position, velocity and also the start offset of the bullets.

In the while loop we use math.atan2 to calculate the angle to the target which is then used to rotate the cannon image and passed to the Bullet instances. In the __init__ method of the Bullets we rotate the offset vector, velocity vector and the sprite image by the angle.

To move the bullet, we add the (rotated) velocity vector to the position vector and set the rect position to the pos vector. The rect has to be moved, because it holds the blit position and is used for collision detection.

import math
import pygame as pg
from pygame.math import Vector2


pg.init()
screen = pg.display.set_mode((640, 480))
FONT = pg.font.Font(None, 24)
BLACK = pg.Color('black')
BULLET_IMAGE = pg.Surface((20, 11), pg.SRCALPHA)
pg.draw.polygon(BULLET_IMAGE, pg.Color('grey11'), [(0, 0), (20, 5), (0, 11)])


class Bullet(pg.sprite.Sprite):

    def __init__(self, pos, angle):
        super(Bullet, self).__init__()
        self.image = pg.transform.rotate(BULLET_IMAGE, -angle)
        self.rect = self.image.get_rect(center=pos)
        # To apply an offset to the start position,
        # create another vector and rotate it as well.
        offset = Vector2(40, 0).rotate(angle)
        # Add the offset vector to the position vector.
        self.pos = Vector2(pos) + offset  # Center of the sprite.
        # Rotate the velocity vector (9, 0) by the angle.
        self.velocity = Vector2(9, 0).rotate(angle)

    def update(self):
        # Add velocity to pos to move the sprite.
        self.pos += self.velocity
        self.rect.center = self.pos


def main():
    clock = pg.time.Clock()
    # The cannon image and rect.
    cannon_img = pg.Surface((60, 22), pg.SRCALPHA)
    pg.draw.rect(cannon_img, pg.Color('grey19'), [0, 0, 35, 22])
    pg.draw.rect(cannon_img, pg.Color('grey19'), [35, 6, 35, 10])
    orig_cannon_img = cannon_img  # Store orig image to preserve quality.
    cannon = cannon_img.get_rect(center=(320, 240))
    angle = 0
    # Add bullets to this group.
    bullet_group = pg.sprite.Group()

    playing = True
    while playing:
        for event in pg.event.get():
            if event.type == pg.QUIT:
                playing = False
            elif event.type == pg.MOUSEBUTTONDOWN:
                # Left button fires a bullet from cannon center with
                # current angle. Add the bullet to the bullet_group.
                if event.button == 1:
                    bullet_group.add(Bullet(cannon.center, angle))

        bullet_group.update()
        # Find angle to target (mouse pos).
        x, y = Vector2(pg.mouse.get_pos()) - cannon.center
        angle = math.degrees(math.atan2(y, x))
        # Rotate the cannon image.
        cannon_img = pg.transform.rotate(orig_cannon_img, -angle)
        cannon = cannon_img.get_rect(center=cannon.center)

        # Draw
        screen.fill(pg.Color('darkseagreen4'))
        bullet_group.draw(screen)
        screen.blit(cannon_img, cannon)
        txt = FONT.render('angle {:.1f}'.format(angle), True, BLACK)
        screen.blit(txt, (10, 10))
        pg.draw.line(
            screen, pg.Color(150, 60, 20),
            cannon.center, pg.mouse.get_pos(), 2)
        pg.display.update()

        clock.tick(30)

if __name__ == '__main__':
    main()
    pg.quit()