[英]How to rotate a triangle to a certain angle in pygame?
I need to rotate a triangle (Not an image) around at the center of the screen.我需要在屏幕中心旋转一个三角形(不是图像)。 I have seen other people answer this question, but the triangle could not point upwards.
我见过其他人回答这个问题,但三角形不能向上。
I have tried to use other peoples functions, but they see to only work partly, like the function I mentioned above.我曾尝试使用其他人的功能,但他们认为只能部分工作,例如我上面提到的 function。
import pygame
disp=pygame.display.set_mode((200,200))
import math
def rotate_triange(mouse_pos,triangle_pos):
#The code here
import time
while True:
time.sleep(1)
pygame.Surface.fill(disp,(255,255,255))
center = (100,100)
radius = 10
mouse_position = pygame.mouse.get_pos()
for event in pygame.event.get():
pass
points = rotate_triangle((100,100),mouse_position)
pygame.draw.polygon(disp,(0,0,0),points)
pygame.display.update()
In pygame 2 dimensional vector arithmetic is implemented in pygame.math.Vector2
.在 pygame 中,二维向量算术在
pygame.math.Vector2
中实现。
Define a Vector2
object for the mouse position and the center of the triangle.为鼠标 position 和三角形的中心定义一个
Vector2
object。 Calculate the angle of vector form the center point to the mouse position ( .angle_to()
):计算向量从中心点到鼠标 position 的角度(
.angle_to()
):
vMouse = pygame.math.Vector2(mouse_pos)
vCenter = pygame.math.Vector2(center)
angle = pygame.math.Vector2().angle_to(vMouse - vCenter)
Define the 3 points of the triangle around the (0, 0) and rotate them by the angle (.rotate()
)围绕 (0, 0) 定义三角形的 3 个点并将它们旋转角度(
.rotate()
)
points = [(-0.5, -0.866), (-0.5, 0.866), (2.0, 0.0)]
rotated_point = [pygame.math.Vector2(p).rotate(angle) for p in points]
To calculate the final points, the points have to b scaled and translated by the center of the triangle:要计算最终点,这些点必须按三角形中心进行缩放和平移:
triangle_points = [(vCenter + p*scale) for p in rotated_point]
See the example:请参阅示例:
import pygame
import math
def rotate_triangle(center, scale, mouse_pos):
vMouse = pygame.math.Vector2(mouse_pos)
vCenter = pygame.math.Vector2(center)
angle = pygame.math.Vector2().angle_to(vMouse - vCenter)
points = [(-0.5, -0.866), (-0.5, 0.866), (2.0, 0.0)]
rotated_point = [pygame.math.Vector2(p).rotate(angle) for p in points]
triangle_points = [(vCenter + p*scale) for p in rotated_point]
return triangle_points
disp=pygame.display.set_mode((200,200))
run = True
while run:
for event in pygame.event.get():
if event.type == pygame.QUIT:
run = False
mouse_position = pygame.mouse.get_pos()
points = rotate_triangle((100, 100), 10, mouse_position)
pygame.Surface.fill(disp, (255,255,255))
pygame.draw.polygon(disp, (0,0,0), points)
pygame.display.update()
A version of the algorithm, without the use of pygame.math.Vector2
, looks as follows:该算法的一个版本,没有使用
pygame.math.Vector2
,如下所示:
def rotate_triangle(center, scale, mouse_pos):
dx = mouse_pos[0] - center[0]
dy = mouse_pos[1] - center[1]
len = math.sqrt(dx*dx + dy*dy)
dx, dy = (dx*scale/len, dy*scale/len) if len > 0 else (1, 0)
pts = [(-0.5, -0.866), (-0.5, 0.866), (2.0, 0.0)]
pts = [(center[0] + p[0]*dx + p[1]*dy, center[1] + p[0]*dy - p[1]*dx) for p in pts]
return pts
Note this version is probably faster.请注意,此版本可能更快。 It needs a
math.sqrt
operation, in compare to math.atan2
which is probably used by .angle_to()
and math.sin
respectively math.cos
which is probably used by .rotate()
, of the former algorithm.与前一种算法的
.angle_to()
和math.sin
可能分别使用的math.cos
可能由.rotate()
() 使用的math.atan2
相比,它需要一个math.sqrt
操作。 The result coordinates are the same.结果坐标相同。
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