simple projection example in pure python. no gpu. uses pyglm for some vector math

cube.py

import pygame
from pyglm.glm import vec2, vec3, vec4
from pyglm import glm


def to_screen(point: vec2, screen_v: vec2) -> vec2:
    """
    ndc (-1, 1) to actual screen coords (0, width), (0, height)
    """
    n = (point + 1) / 2  # (0, 1)
    return vec2(n.x, 1 - n.y) * screen_v


def main():
    pygame.init()

    win = pygame.Window(size=(800, 800))

    screen = win.get_surface()
    screen_v = vec2(screen.width, screen.height)
    clock = pygame.Clock()

    points = [
        vec3(1, 1, 1),
        vec3(1, 1, -1),
        vec3(1, -1, -1),
        vec3(1, -1, 1),
        vec3(-1, 1, 1),
        vec3(-1, 1, -1),
        vec3(-1, -1, -1),
        vec3(-1, -1, 1),

        # vec3(.5, 2, 1),
        # vec3(-.5, 2, 1),
    ]

    faces: list[list[int]] = [
        [0, 1, 2, 3],
        [4, 5, 6, 7],
        [0, 4],
        [1, 5],
        [2, 6],
        [3, 7],
        # [8, 9],
    ]

    angle = 0.0
    axis = glm.normalize(vec3(0, 1, 0))

    while True:
        delta = clock.tick(60) / 1000
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                pygame.quit()
                return

        screen.fill('black')

        angle += 2 * delta

        rotation = glm.rotate(angle, glm.normalize(axis))
        translation = glm.translate(vec3(0, 0, 10))
        scale = glm.scale(vec3(1, 1, 1))
        model = translation * scale * rotation

        view = glm.lookAt(vec3(0, 0, 0), vec3(0, 0, 1), vec3(0, 1, 0))
        proj = glm.perspective(glm.radians(60), screen.width / screen.height, 0.1, 100.0)
        mvp = proj * view * model

        transformed_points = []
        for point in points:
            clip = mvp * vec4(point, 1)
            ndc = vec3(clip) / clip.w
            transformed_points.append(to_screen(ndc.xy, screen_v))

        for face in faces:
            for i, points_index in enumerate(face):
                screen_point = transformed_points[points_index]
                next_point = transformed_points[face[(i + 1) % len(face)]]

                pygame.draw.line(screen, 'red', screen_point, next_point, 2)

        win.flip()


if __name__ == '__main__':
    main()