my first ever Python program has hit a block I don't think I have the knowledge to solve myself.
It's a controllable spaceship on a 2d surface, I want to add momentum / inertia I have it so the ship keeps travelling on the vector it previously was, when the engine is stopped. However I can only get it to 'snap' to the new vector it rotates to face instantly.
What I want to happen is that inertia vector slowly aligns with the new pointing vector as it accelerates- like rotational acceleration? ( I'm not too hot on the math ) - I can rotate the inertia vector , but I would need to compare it somehow with the new pointing vector , and modify it based upon their difference?
if anyone could advise as to how I might start to approach this, that would be great - I suspect I coming at this from completely the wrong way. Heres some of the code ( be gentle please!)
the sprite used is this : - ship.png
import pygame
import sys
from math import sin, cos, pi, atan2
from pygame.locals import *
import random
from random import randint
from pygame.math import Vector2
import operator
"""solar system generator"""
"""set screen size and center and some global namespace colors for ease of use"""
globalalpha = 255
screenx = int(1200)
screeny = int(700)
centerx = int(screenx / 2)
centery = int(screeny / 2)
center = (centerx, centery)
black = ( 0, 0, 0)
white = (255, 255, 255)
red = (209, 2, 22)
TRANSPARENT = (255,0,255)
numstars = 150
DISPLAYSURF = pygame.display.set_mode((screenx, screeny), 0, 32)
clock = pygame.time.Clock()
globaltimefactor = 1
shipimage = pygame.image.load('ship.png').convert()
DISPLAYSURF.fill(black)
screen_rect = DISPLAYSURF.get_rect()
class Playership(pygame.sprite.Sprite):
def __init__(self):
super().__init__()
self.imageorig = pygame.image.load('ship.png').convert_alpha()
self.startpos = (screen_rect.center)
self.image = self.imageorig.copy()
self.rect = self.imageorig.get_rect(center=self.startpos)
self.angle = 0
self.currentposx = 600
self.currentposy = 350
self.tuplepos = (self.currentposx, self.currentposy)
self.speed = 1
self.rotatespeed = 1.5
self.initialvec = (600, 0)
self.destination = 0
self.anglechange = 0
self.currentspeed = 0
self.maxspeed = 5
self.engineon = False
self.newvec = (600, 0)
self.newdestination = 0
self.acceleration = 0.015
self.inertiaspeed = 0
self.transitionalvec = self.initialvec
def get_angleafterstopping(self):
newvec = self.initialvec
self.newvec = newvec
def get_destinationafterstopping(self):
x_dist = self.newvec[0] - self.tuplepos[0]
y_dist = self.newvec[1] - self.tuplepos[1]
self.newdestination = atan2(-y_dist, x_dist) % (2 * pi)
def get_destination(self):
x_dist = self.initialvec[0] - self.tuplepos[0]
y_dist = self.initialvec[1] - self.tuplepos[1]
self.destination = atan2(-y_dist, x_dist) % (2 * pi)
def moveship(self):
if self.engineon is True:
self.currentspeed = self.currentspeed + self.acceleration
if self.currentspeed > self.maxspeed:
self.currentspeed = self.maxspeed
elif self.currentspeed < 0:
self.currentspeed = 0
self.inertiaspeed = self.currentspeed
elif self.engineon is False:
self.currentposx = self.currentposx + (cos(self.newdestination) * self.inertiaspeed * globaltimefactor)
self.currentposy = self.currentposy - (sin(self.newdestination) * self.inertiaspeed * globaltimefactor)
self.tuplepos = (self.currentposx, self.currentposy)
self.rect.center = self.tuplepos
return
self.get_destination()
self.currentposx = self.currentposx + (cos(self.destination) * self.currentspeed * globaltimefactor)
self.currentposy = self.currentposy - (sin(self.destination) * self.currentspeed * globaltimefactor)
self.tuplepos = (self.currentposx, self.currentposy)
self.rect.center = self.tuplepos
def rotateship(self, rotation):
self.anglechange = self.anglechange - (rotation * self.rotatespeed * globaltimefactor)
self.angle += (rotation * self.rotatespeed * globaltimefactor)
self.image = pygame.transform.rotate(self.imageorig, self.angle)
self.rect = self.image.get_rect(center=self.rect.center)
initialvec = self.tuplepos + Vector2(0, -600).rotate(self.anglechange * globaltimefactor)
initialvec = int(initialvec.x), int(initialvec.y)
self.initialvec = initialvec
myship = Playership()
all_sprites_list = pygame.sprite.Group()
all_sprites_list.add(myship)
firsttimedone = False
def main():
done = False
while not done:
keys_pressed = pygame.key.get_pressed()
if keys_pressed[pygame.K_LEFT]:
myship.rotateship(1)
if keys_pressed[pygame.K_RIGHT]:
myship.rotateship(-1)
if keys_pressed[pygame.K_UP]:
myship.engineon = True
myship.moveship()
for event in pygame.event.get():
if event.type == pygame.QUIT:
pygame.quit(); sys.exit();
if event.type == pygame.KEYUP:
if event.key == pygame.K_UP:
myship.engineon = False
myship.currentspeed = 0
myship.get_angleafterstopping()
myship.get_destinationafterstopping()
DISPLAYSURF.fill(black)
all_sprites_list.update()
all_sprites_list.draw(DISPLAYSURF)
pygame.draw.line(DISPLAYSURF, white, (myship.tuplepos), (myship.initialvec))
pygame.draw.line(DISPLAYSURF, red, (myship.tuplepos), (myship.newvec))
pygame.display.flip()
if myship.engineon is False:
myship.moveship()
clock.tick(50)
pygame.display.set_caption("fps: " + str(clock.get_fps()))
if __name__ == '__main__':
pygame.init()
main()
pygame.quit(); sys.exit();
EDIT :
I fixed it : just required a better understanding of vectors ship starts off with acceleration and velocity both stated as vectors.
self.position = vec(screenx / 2, screeny / 2)
self.vel = vec(0, 0)
self.acceleration = vec(0, -0.2) # The acceleration vec points upwards from the starting ship position
rotating the ship rotates that vector in place
self.acceleration.rotate_ip(self.angle_speed)
self.angle += self.angle_speed
self.image = pygame.transform.rotate(self.imageorig, -self.angle)
self.rect = self.image.get_rect(center=self.rect.center)
accelerating is this :
self.vel += self.acceleration * self.enginepower * globaltimefactor
updating position :
self.position += self.vel
self.rect.center = self.position
I was making it harder than it needed to be, velocity needed to be constant until acted upon by the rotated acceleration vector. I didn't know how to add vectors together etc.
