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[Python / pyGame] Rotate image towards mouse pointer


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#1 viper34j   Members   -  Reputation: 122

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Posted 08 October 2010 - 09:17 AM

Oh great internetmenz, I need your help. My decade old math skills are failing me.

I'm attempting to rotate an image towards a point using pygame. The point is the mouse cursor in this case. Here is an example of my issue (this is only a snippet):


src_image, rect = pygame.image.load('c:\\testimage.png')
screen = pygame.display.get_surface()

# Example values
player_angle = 0
player_position = (100,100)

# Get the mouse point (Something between (0,0) and (1024,800)).
mouse_point = pygame.mouse.get_pos()

# Set the old_center for repositioning after the rotate.
old_center = self.rect.center

# *** Heres my problem, how do I determine what the angle is from the player_angle
# to the mouse_point with only these three peices of information.
angle_to_mouse = ??

image = pygame.transform.rotate(self.src_image, angle_to_mouse)
rect = image.get_rect()
rect.center = old_center




How do I determine the angle from the center point of the player_point to the mouse_point?

Thanks!

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#2 unbird   Crossbones+   -  Reputation: 6012

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Posted 08 October 2010 - 09:52 AM

Never used pygame, but what you are looking for is calculating an angle given a difference vector, in your case player_position - mouse_point. This will give you a (relative) x and y which you feed to atan2. Search the python math lib for this function, I bet it exists. This will give you the angle in radians which you can then feed to the rotate function (angle_to_mouse). Don't know what coordinate system you are using (left/right-handed), so probably you will have to negate y prior to the atan2 call (or negate angle_to_mouse).

#3 Esys   Members   -  Reputation: 156

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Posted 08 October 2010 - 10:08 AM


angle_to_pointer = math.degrees(math.atan2(objectY-mouseY, objectX-mouseX))+180



#4 viper34j   Members   -  Reputation: 122

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Posted 08 October 2010 - 02:22 PM

Thanks guys, that helped out a lot.




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