Rotating 3D Cube using Python and Pygame

In one of my previous tutorials, I have shown how to make a simulation of a wireframe cube using Python and Pygame. Today, we will make a few modifications in the code from that tutorial to make an awesome rotating solid cube. See below the video of the rotating cube.

NOTE: If you want to stay updated, consider following me on twitter at http://twitter.com/codentronix.

Click here to download the source code.

The Code

"""
 Simulation of a rotating 3D Cube
 Developed by Leonel Machava <[email protected]>

http://codeNtronix.com

"""
import sys, math, pygame
from operator import itemgetter

class Point3D:
    def __init__(self, x = 0, y = 0, z = 0):
        self.x, self.y, self.z = float(x), float(y), float(z)

    def rotateX(self, angle):
        """ Rotates the point around the X axis by the given angle in degrees. """
        rad = angle * math.pi / 180
        cosa = math.cos(rad)
        sina = math.sin(rad)
        y = self.y * cosa - self.z * sina
        z = self.y * sina + self.z * cosa
        return Point3D(self.x, y, z)

    def rotateY(self, angle):
        """ Rotates the point around the Y axis by the given angle in degrees. """
        rad = angle * math.pi / 180
        cosa = math.cos(rad)
        sina = math.sin(rad)
        z = self.z * cosa - self.x * sina
        x = self.z * sina + self.x * cosa
        return Point3D(x, self.y, z)

    def rotateZ(self, angle):
        """ Rotates the point around the Z axis by the given angle in degrees. """
        rad = angle * math.pi / 180
        cosa = math.cos(rad)
        sina = math.sin(rad)
        x = self.x * cosa - self.y * sina
        y = self.x * sina + self.y * cosa
        return Point3D(x, y, self.z)

    def project(self, win_width, win_height, fov, viewer_distance):
        """ Transforms this 3D point to 2D using a perspective projection. """
        factor = fov / (viewer_distance + self.z)
        x = self.x * factor + win_width / 2
        y = -self.y * factor + win_height / 2
        return Point3D(x, y, self.z)

class Simulation:
    def __init__(self, win_width = 640, win_height = 480):
        pygame.init()

        self.screen = pygame.display.set_mode((win_width, win_height))
        pygame.display.set_caption("Simulation of a rotating 3D Cube (http://codeNtronix.com)")

        self.clock = pygame.time.Clock()

        self.vertices = [
            Point3D(-1,1,-1),
            Point3D(1,1,-1),
            Point3D(1,-1,-1),
            Point3D(-1,-1,-1),
            Point3D(-1,1,1),
            Point3D(1,1,1),
            Point3D(1,-1,1),
            Point3D(-1,-1,1)
        ]

        # Define the vertices that compose each of the 6 faces. These numbers are
        # indices to the vertices list defined above.
        self.faces  = [(0,1,2,3),(1,5,6,2),(5,4,7,6),(4,0,3,7),(0,4,5,1),(3,2,6,7)]

        # Define colors for each face
        self.colors = [(255,0,255),(255,0,0),(0,255,0),(0,0,255),(0,255,255),(255,255,0)]

        self.angle = 0

    def run(self):
        """ Main Loop """
        while 1:
            for event in pygame.event.get():
                if event.type == pygame.QUIT:
                    pygame.quit()
                    sys.exit()

            self.clock.tick(50)
            self.screen.fill((0,32,0))

            # It will hold transformed vertices.
            t = []

            for v in self.vertices:
                # Rotate the point around X axis, then around Y axis, and finally around Z axis.
                r = v.rotateX(self.angle).rotateY(self.angle).rotateZ(self.angle)
                # Transform the point from 3D to 2D
                p = r.project(self.screen.get_width(), self.screen.get_height(), 256, 4)
                # Put the point in the list of transformed vertices
                t.append(p)

            # Calculate the average Z values of each face.
            avg_z = []
            i = 0
            for f in self.faces:
                z = (t[f[0]].z + t[f[1]].z + t[f[2]].z + t[f[3]].z) / 4.0
                avg_z.append([i,z])
                i = i + 1

            # Draw the faces using the Painter's algorithm:
            # Distant faces are drawn before the closer ones.
            for tmp in sorted(avg_z,key=itemgetter(1),reverse=True):
                face_index = tmp[0]
                f = self.faces[face_index]
                pointlist = [(t[f[0]].x, t[f[0]].y), (t[f[1]].x, t[f[1]].y),
                             (t[f[1]].x, t[f[1]].y), (t[f[2]].x, t[f[2]].y),
                             (t[f[2]].x, t[f[2]].y), (t[f[3]].x, t[f[3]].y),
                             (t[f[3]].x, t[f[3]].y), (t[f[0]].x, t[f[0]].y)]
                pygame.draw.polygon(self.screen,self.colors[face_index],pointlist)

            self.angle += 1

            pygame.display.flip()

if __name__ == "__main__":
    Simulation().run()

If you liked this experiment, please consider leaving a comment, or sharing this post using one of the buttons below, or subscribing to the blog.

  1. Hi there, I found your site via Google at the same time as searching for a similar matter, your web site got here up, it seems to be great. I have bookmarked it in my google bookmarks.

  2. Great, but if you had the work to define a point class, why not a face class too? :)

    • Hello Nic. Undoubtedly, a face class would contribute to a good (OO) design and a more elegant code. However, my intention was to keep it as simple as possible. As you can see the simulation was made using very few lines of code.

      I will leave the improvement of the code as an exercise for my readers. :)

  3. hello!very nice work!i found samples of your work from google and i was wondering if you can help me with a project i am preparing.i want to connect a basic atom pro 28 via usb to blender and i want to be able to control the rotation of an object with a potentiometer.can you plz guide me because i am new in the programming

Leave a Comment

Notify me of followup comments via e-mail. You can also subscribe without commenting.