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Вот ссылка на коды, и вы можете поиграть с программой: https://py3.codeskulptor.org/#user306_KJotPenLg75Fx0e_6.py

 import simplegui
import math
import codeskulptor

width,height=800,550
center=(width/2,height/2)
keys=0
pi=3.1415926535897932384626433832795
#Camera
cam_pos=[0,0,0] 
cam_speed=5
rotate_speed=pi/90#radians
yaw,pitch=0,0
W,R,A,S,D,F,DOWN,UP,LEFT,RIGHT=False,False,False,False,False,False,False,False,False,False
#The distance between the camera and the canvas. 
canvas_distance=400  
#input a 3d point, return the projected position on the canvas                           
def projection(pos):   
    delta_x=-pos[0]
    delta_y=-pos[1]
    delta_z=-pos[2]
    if delta_z==canvas_distance:return(center[0]-delta_x,center[1] delta_y)
    if 0<delta_z<canvas_distance:return (center[0]-(delta_x/delta_z)*canvas_distance,center[1] (delta_y/delta_z)*canvas_distance)
    if delta_z<=0:return (center[0]-delta_x*10000,center[1] delta_y*10000)
    ratio=canvas_distance/delta_z
    return [center[0]-delta_x*ratio,center[1] delta_y*ratio]

#rotate around the camera
def rotation(pos):
    #yaw changes x and z
    if LEFT==True or RIGHT==True:
        cosine=math.cos(yaw)
        sine=math.sin(yaw)
        pos[2]=cosine*pos[2] sine*pos[0]
        pos[0]=cosine*pos[0]-sine*pos[2]
    #pitch changes y and z
    elif UP==True or DOWN==True:
        cosine=math.cos(pitch)
        sine=math.sin(pitch)
        pos[1]=cosine*pos[1] sine*pos[2]
        pos[2]=cosine*pos[2]-sine*pos[1] 
    return pos

def cam_update():
    global yaw,pitch
    if W==True:translate(2,cam_speed)
    elif S==True:translate(2,-cam_speed)  
    if A==True:translate(0,cam_speed)
    elif D==True:translate(0,-cam_speed)  
    if R==True:translate(1,-cam_speed)
    elif F==True:translate(1, cam_speed)                            
    if LEFT==True or RIGHT==True or UP==True or DOWN==True:    
        if LEFT==True:yaw=rotate_speed
        elif RIGHT==True:yaw=-rotate_speed  
        if UP==True:pitch=rotate_speed
        elif DOWN==True:pitch=-rotate_speed
        rotate()
        
def keyup(key):
    global W,R,A,S,D,F,DOWN,UP,LEFT,RIGHT,keys
    keys-=1
    if  key==simplegui.KEY_MAP['W']:W=False     
    elif key==simplegui.KEY_MAP['S']:S=False
    elif key==simplegui.KEY_MAP['A']:A=False
    elif key==simplegui.KEY_MAP['D']:D=False
    elif key==simplegui.KEY_MAP['R']:R=False
    elif key==simplegui.KEY_MAP['F']:F=False
    elif key==simplegui.KEY_MAP['up']:UP=False
    elif key==simplegui.KEY_MAP['down']:DOWN=False
    elif key==simplegui.KEY_MAP['left']:LEFT=False
    elif key==simplegui.KEY_MAP['right']:RIGHT=False
def keydown(key):
    global W,R,A,S,D,F,DOWN,UP,LEFT,RIGHT,keys
    keys =1
    #move forward amp; backward
    if  key==simplegui.KEY_MAP['W']:W,S=True,False     
    elif key==simplegui.KEY_MAP['S']:S,W=True,False
    #move left amp; right
    elif key==simplegui.KEY_MAP['A']:A,D=True,False
    elif key==simplegui.KEY_MAP['D']:D,A=True,False
    #levitate amp; fall
    elif key==simplegui.KEY_MAP['R']:R,F=True,False
    elif key==simplegui.KEY_MAP['F']:F,R=True,False
    #pitch
    elif key==simplegui.KEY_MAP['up']:UP,DOWN=True,False
    elif key==simplegui.KEY_MAP['down']:DOWN,UP=True,False
    #yaw
    elif key==simplegui.KEY_MAP['left']:LEFT,Right=True,False
    elif key==simplegui.KEY_MAP['right']:RIGHT,LEFT=True,False                                                                                
def find_distance(a,b):
    if len(a)==2:return math.sqrt((a[0]-b[0])**2 (a[1]-b[1])**2)
    return math.sqrt((a[0]-b[0])**2 (a[1]-b[1])**2 (a[2]-b[2])**2)
    
class Point:
    def __init__(self,name,color,loc):
        self.name=name
        self.loc=loc#(x,y,z)
        self.color=color
        self.pos=projection(self.loc)#canvas position

#Declaring Point objects
x=Point('X','red',[800,-180,-1300])
y=Point('Y','blue',[-200,820,-1300])
z=Point('Z','green',[-200,-180,-300])
origin=Point('O','white',[-200,-180,-1300])
points=[x,y,z,origin]

#translate all points        
def translate(axis,units):
    for point in points:point.loc[axis] =units  
#rotate all points
def rotate():
    for point in points:point.loc=rotation(point.loc) 

#this function executes 60 times a second        
def draw(canvas):   
    for point in points:
        canvas.draw_line(origin.pos,point.pos,3,point.color)
        canvas.draw_text(point.name str([int(x) for x in point.loc]),point.pos,15,'white') 
    
    #if any keys are pressed, update points' locations   
    if keys>0:
        cam_update()
        for point in points:
            point.pos=projection(point.loc)    
    canvas.draw_text('distance between Z and O: ' str(find_distance(z.loc,origin.loc)),[15,20],20,'yellow')
                     
frame = simplegui.create_frame("SSS 3D", width, height)
frame.set_draw_handler(draw)
frame.set_keydown_handler(keydown)
frame.set_keyup_handler(keyup)
label=frame.add_label('Click the canvas first')
label=frame.add_label('To move: WASD RF')
label=frame.add_label('To yaw or pitch: arrow keys')
frame.start()
 

Когда я пытаюсь повернуть, расстояние между двумя точками уменьшается. Вы можете видеть, что оси в моем примере продолжают уменьшаться. Также похоже, что углы между осями становятся все более и более острыми.

Решаемая. Проблема с точностью. Мне просто нужно уменьшить промежуточные переменные и вернуть значение в одном длинном вычислении.