Graphical Glitches in PyOpenGL with PyGame

Question

I am currently programming a game with PyOpenGL with PyGame, and when using Vertex Buffers, graphical glitches occur. The glitches include lines being drawn between each model when it shouldn't. I have found that alternating between Ground() and GroundVBO() does not cause any graphical glitches most of the time. Is there anything that I am missing?

global vbo
vbo = 0
def Ground():
    glBegin(GL_LINES)
    for edge in ground_edges:
        for vertex in edge:
            glVertex3fv(ground_verticies[vertex])
    glEnd()
def GroundVBO():
    for edge in ground_edges:
        for vertex in edge:
            ground_noot = glVertex3fv(ground_verticies[vertex])
    vbo = glGenBuffers(1)
    glBindBuffer (GL_ARRAY_BUFFER, vbo)
    glBufferData (GL_ARRAY_BUFFER, len(ground_verticies)*4, ground_noot, GL_STATIC_DRAW)
    glVertexPointer (3, GL_FLOAT, 0, None)
    glDrawArrays(GL_LINES, 0, 300)

I believe what was causing the problem was specifying the vertices outside the glBegin/glEnd. All I have to do now is rewrite some of the code, and it should work! — ElongatedYeet
– ElongatedYeet, Commented May 10, 2020 at 22:57
I have now got it to work, I was stuck on the array of numbers for the vertex pointer, as I was appending the entire vertex which had brackets around it. What I had to do was append each point individually so there were do brackets. — ElongatedYeet
– ElongatedYeet, Commented May 13, 2020 at 1:11

Rabbid76 · Accepted Answer · 2020-05-05 07:21:58Z

1

If you want to use fixed function attributes, then you have to enable the client-side capability by glEnableClientState. Specifying the vertices by glVertex3fv in a loop is superfluous. Specifying a vertex outside a glBegin/glEnd sequence results in undefined behavior.
The last parameter to glDrawArrays is the number of vertex coordinates:

def GroundVBO():

    vbo = glGenBuffers(1)
    glBindBuffer(GL_ARRAY_BUFFER, vbo)
    glBufferData(GL_ARRAY_BUFFER, len(ground_verticies)*4, ground_noot, GL_STATIC_DRAW)

    glEnableClientState(GL_VERTEX_ARRAY)
    glVertexPointer(3, GL_FLOAT, 0, None)
    glDrawArrays(GL_LINES, 0, len(ground_verticies))
    glDisableClientState(GL_VERTEX_ARRAY)

answered May 5, 2020 at 7:21

Rabbid76

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