CODEWITHSUNDEEP
pythonpython-3.xopenglpygamepyopengl
Hippolippo
Hippolippo

Reputation: 813

How to use face culling and depth test in pyopengl

I am working on a program for school that uses 3D shapes and I need to figure out how to make a solid cube. When I make the cube I end up with this:enter image description here

I noticed that it is drawing the shapes in the order that I defined them. I then tried to find a solution to this problem because I am sure many other people have a similar problem and I run into something called face culling which has all the faces points be defined counterclockwise when facing out so when it is rendered it would be drawn clockwise and opengl can notice that and not draw them.
I tried using this and It still ended up with the same result so I am confused about what I have done wrong.

import pygame
import time
from pygame.locals import *
from OpenGL.GL import *
from OpenGL.GLU import *

block = [
    [0,1,0],
    [1,0,0],
    [1,0,1],
    [0,0,1],
    [1,1,0],
    [0,1,1]
]

def Cube(x,y,z):
    glBegin(GL_TRIANGLES)
    glColor3f(block[0][0], block[0][1], block[0][2])  # N
    glVertex3f(x + .5, y + 1, z + .5)
    glVertex3f(x - .5, y + 1, z + .5)
    glVertex3f(x - .5, y, z + .5)
    glVertex3f(x - .5, y, z + .5)
    glVertex3f(x + .5, y, z + .5)
    glVertex3f(x + .5, y + 1, z + .5)
    glColor3f(block[1][0], block[1][1], block[1][2])  # S
    glVertex3f(x - .5, y + 1, z - .5)
    glVertex3f(x + .5, y + 1, z - .5)
    glVertex3f(x + .5, y, z - .5)
    glVertex3f(x + .5, y, z - .5)
    glVertex3f(x - .5, y, z - .5)
    glVertex3f(x - .5, y + 1, z - .5)
    glColor3f(block[2][0], block[2][1], block[2][2])  # W
    glVertex3f(x + .5, y + 1, z - .5)
    glVertex3f(x + .5, y + 1, z + .5)
    glVertex3f(x + .5, y, z + .5)
    glVertex3f(x + .5, y, z + .5)
    glVertex3f(x + .5, y, z - .5)
    glVertex3f(x + .5, y + 1, z - .5)
    glColor3f(block[3][0], block[3][1], block[3][2])  # E
    glVertex3f(x - .5, y + 1, z + .5)
    glVertex3f(x - .5, y + 1, z - .5)
    glVertex3f(x - .5, y, z - .5)
    glVertex3f(x - .5, y, z - .5)
    glVertex3f(x - .5, y, z + .5)
    glVertex3f(x - .5, y + 1, z + .5)
    glColor3f(block[4][0], block[4][1], block[4][2])  # U
    glVertex3f(x + .5, y + 1, z - .5)
    glVertex3f(x - .5, y + 1, z - .5)
    glVertex3f(x - .5, y + 1, z + .5)
    glVertex3f(x - .5, y + 1, z + .5)
    glVertex3f(x + .5, y + 1, z + .5)
    glVertex3f(x + .5, y + 1, z - .5)
    glColor3f(block[5][0], block[5][1], block[5][2])  # D
    glVertex3f(x + .5, y, z + .5)
    glVertex3f(x + .5, y, z - .5)
    glVertex3f(x - .5, y, z - .5)
    glVertex3f(x - .5, y, z - .5)
    glVertex3f(x - .5, y, z + .5)
    glVertex3f(x + .5, y, z + .5)
    glEnd()
def main():
    pygame.init()
    display = (800,600)
    glClearColor(0.0, 0.0, 0.0, 0.0)
    glClearDepth(1.0)

    glDepthMask(GL_TRUE)
    glDepthFunc(GL_LESS)
    glEnable(GL_DEPTH_TEST)
    glEnable(GL_CULL_FACE)
    glCullFace(GL_BACK)
    glFrontFace(GL_CCW)
    glShadeModel(GL_SMOOTH)
    glDepthRange(0.0,1.0)
    pygame.display.set_mode(display, DOUBLEBUF|OPENGL)
    gluPerspective(45, (display[0]/display[1]), 0.1, 100.0)
    glTranslatef(0.0, 0.0, -5)
    while True:

        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                pygame.quit()
                quit()
        glRotatef(1, 3, 1, 1,)
        glClearDepth(1.0)
        glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT)
        Cube(0,0,0)
        glCullFace(GL_BACK)
        pygame.display.flip()
        time.sleep(.01)




main()

Upvotes: 0

Views: 901

Answers (1)

Rabbid76
Rabbid76

Reputation: 210878

The (OpenGL) display mode has been set, before any OpenGL instruction is called, else it won't have any effect or even cause an error:

pygame.display.set_mode(display, DOUBLEBUF|OPENGL)

glClearColor(0.0, 0.0, 0.0, 0.0)
glClearDepth(1.0)

glDepthMask(GL_TRUE)
glDepthFunc(GL_LESS)
glEnable(GL_DEPTH_TEST)
glEnable(GL_CULL_FACE)
glCullFace(GL_BACK)
glFrontFace(GL_CCW)
glShadeModel(GL_SMOOTH)
glDepthRange(0.0,1.0)

If you do so, the the Depth Test will work and the mesh is drawn correctly.

By the way not all of the faces are drawn with counter clockwise winding order. It has to be:

def Cube(x,y,z):
    glBegin(GL_TRIANGLES)
    glColor3f(block[0][0], block[0][1], block[0][2])  # N
    glVertex3f(x + .5, y + 1, z + .5)
    glVertex3f(x - .5, y + 1, z + .5)
    glVertex3f(x - .5, y,     z + .5)
    glVertex3f(x - .5, y,     z + .5)
    glVertex3f(x + .5, y,     z + .5)
    glVertex3f(x + .5, y + 1, z + .5)
    glColor3f(block[1][0], block[1][1], block[1][2])  # S
    glVertex3f(x - .5, y + 1, z - .5)
    glVertex3f(x + .5, y + 1, z - .5)
    glVertex3f(x + .5, y,     z - .5)
    glVertex3f(x + .5, y,     z - .5)
    glVertex3f(x - .5, y,     z - .5)
    glVertex3f(x - .5, y + 1, z - .5)
    glColor3f(block[2][0], block[2][1], block[2][2])  # W
    glVertex3f(x + .5, y + 1, z - .5)
    glVertex3f(x + .5, y + 1, z + .5)
    glVertex3f(x + .5, y,     z + .5)
    glVertex3f(x + .5, y,     z + .5)
    glVertex3f(x + .5, y,     z - .5)
    glVertex3f(x + .5, y + 1, z - .5)
    glColor3f(block[3][0], block[3][1], block[3][2])  # E
    glVertex3f(x - .5, y + 1, z + .5)
    glVertex3f(x - .5, y + 1, z - .5)
    glVertex3f(x - .5, y,     z - .5)
    glVertex3f(x - .5, y,     z - .5)
    glVertex3f(x - .5, y,     z + .5)
    glVertex3f(x - .5, y + 1, z + .5)
    glColor3f(block[4][0], block[4][1], block[4][2])  # U
    glVertex3f(x + .5, y + 1, z - .5)
    glVertex3f(x - .5, y + 1, z - .5)
    glVertex3f(x - .5, y + 1, z + .5)
    glVertex3f(x - .5, y + 1, z + .5)
    glVertex3f(x + .5, y + 1, z + .5)
    glVertex3f(x + .5, y + 1, z - .5)
    glColor3f(block[5][0], block[5][1], block[5][2])  # D
    glVertex3f(x + .5, y, z - .5)
    glVertex3f(x + .5, y, z + .5)
    glVertex3f(x - .5, y, z + .5)
    glVertex3f(x - .5, y, z + .5)
    glVertex3f(x - .5, y, z - .5)
    glVertex3f(x + .5, y, z - .5)
    glEnd()

Upvotes: 3

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