[Python] When I try to move the camera forward the object rotates

In my 3D renderer with Matplotlib, when I try to move the camera forward, the object rotates:

import matplotlib.pyplot as plt
import numpy as np
import math
import GetPolyData as poly


def project_3d_to_2d(x, y, z, d):
# Calculate the angle of projection
theta = math.atan2(z, d)

# Calculate the projected x and y coordinates
projected_x = x * math.cos(theta) - y * math.sin(theta)
projected_y = x * math.sin(theta) + y * math.cos(theta)

return projected_x, projected_y

def Project_Polygon(polygon,d,cam):
CamX = cam[0]
CamY = cam[1]
CamZ = cam[2]
X = []
Y = []
for point in polygon:
x = (point[0]-CamX)
y = (point[1]-CamY)
z = (point[2]-CamZ)
X1,Y1=(project_3d_to_2d(x,y,z,d))
#print(X1,Y1)
X.append(X1)
Y.append(Y1)
return X,Y

def Render(polygons,d,cam):
x=[]
y=[]
for polygon in polygons:
if not Polygon_Behind_Camera:
pass
else:
X,Y = Project_Polygon(polygon,d,cam)
#print(x,y)
for item in X:
x.append(item)
for item in Y:
y.append(item)
return x,y

# Initial render:
model_name = 'monkey.obj'
polygons = poly.extract_polygons_from_obj(model_name)
d = 100
cam = [0,0,0,0,0]
x,y = Render(polygons,d,cam)

# Start display:
plt.ion()
fig = plt.figure()
ax = fig.add_subplot(111)
display, = ax.plot(x, y, 'b-')

# Main loop:
phase = 0
while True:
phase +=1
print(phase)
cam[2] = phase
angle = (cam[3],cam[4])
temp_polygons = polygons
#temp_polygons = rotate_polygons(polygons,cam,angle)

#Prject 3d to 2d
x,y = Render(temp_polygons,d,cam)

#Add the last verticie 1 to the end of every 3 verticies.
tempX = []
tempY = []
for i1 in range(int(len(x)/3)):
for i2 in range(3):
i = i1+i2
item = x
tempX.append(item)
tempX.append(x[i1])
for i1 in range(int(len(y)/3)):
for i2 in range(3):
i = i1+i2
item = y
tempY.append(item)
tempY.append(y[i1])
update(tempX,tempY)


The file(s), 'monkey.obj' is located at https://github.com/CHARSARG/MatPlotRenderer because it's to large.

I've posted an answer, which resolves the issue, but I still don't understand why the function wasn't working. Please edit my answer, or post a new answer if you can explain the issue.

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