Three things you can do to make this more realistic.
1. use self.angle as the argument to pygame.transform.rotate instead of
a_deg, as Joe suggested.
2. use separate variables to keep the car's position. Don't store it in
self.rect.center. This is because rect positions are coerced to ints, so if
your car should be moving 0.5 pixels per frame to the right, this will be
rounded down to 0.
3. update self.rect after you transform. This is because the rotated image
doesn't have the same size as the original image, so its center will be
offset. Also, your second argument to screen.blit should be self.rect, not
self.rect.center. (If you pass it a position like self.rect.center, it will
use that as the upper-left position of the blitted rect.
I modified your file to have this in your init method:
self.x, self.y = SCREEN_SIZE_X/2, SCREEN_SIZE_Y -
self.rect.height * 2
this in your update:
#rotate the car
self.sprite = pygame.transform.rotate(self.original,
self.angle * -1)
self.rect = self.sprite.get_rect(center = self.rect.center)
#move the car
self.x += speedx
self.y += speedy
self.rect = self.sprite.get_rect()
self.rect.center = self.x, self.y
and this in your draw:
screen.blit(self.sprite, self.rect)
And it looked much better to me. Let me know what you think.
-Christopher
On Tue, Aug 30, 2011 at 5:46 AM, Nathan BIAGINI <[email protected]>wrote:
> Hi,
>
> i'm trying to write a car game and i have decided to start by the movement
> part. I calculate the X and Y components of the car and update his position
> by increasing the current one with the two new components. The two
> components depend of the orientation of the car, managed by the right and
> left arrow :
>
>
> speedx = math.sin(self.angle * (math.pi/180)) * SPEED
>> speedy = math.cos(self.angle * (math.pi/180)) * SPEED * -1
>>
>
> Where SPEED is a constant and self.angle a int representing the
> orientation. I don't know if this is the best way because, the car speed
> depends of his orientation. Increasing the self.angle value will increase
> the components, this is not suitable for a car game i think.
>
> I have another problem with the car movement. Each time the orientation
> change, i would like to rotate the car in the right direction. I thought to
> do something like that :
>
> a_rad = math.asin(speedx/SPEED)
>> a_deg = math.degrees(a_rad)
>
> self.sprite = pygame.transform.rotate(self.original, a_deg * -1)
>> self.rect = self.sprite.get_rect(center = self.rect.center)
>>
>
> It does not work properly, this way, my car can't rotate over 90° because
> of the speedx values.
>
> Here is my code :
>
> http://pastebin.com/VJgQRtYq
>
> and the sprite i use for the car is joined.
>
> Thanks for reading me.
>
