OpenGL VBO can run without error but no graphics

Question

The following code should draw a cube each time it is called error code:

draw=False
block_VBO=0
block_EBO=0
block_VAO=0
block_EBO_buffer_len=0
def print_blocks(sx:int,sy:int,sz:int):
    global draw,block_VAO,block_EBO,block_VBO,block_EBO_buffer_len
    if not draw:
        block_point_buffer=[]
        block_color_buffer=[]
        block_EBO_buffer=[]
        block_point_buffer+=[x-0.5,y+0.5,z-0.5,#V0
                            x+0.5,y+0.5,z-0.5,#V1
                            x+0.5,y-0.5,z-0.5,#V2
                            x-0.5,y-0.5,z-0.5,#V3
                            x-0.5,y+0.5,z+0.5,#V4
                            x+0.5,y+0.5,z+0.5,#V5
                            x+0.5,y-0.5,z+0.5,#V6
                            x-0.5,y-0.5,z+0.5]#V7
        block_EBO_buffer+=[0,1,5,4,
                          3,2,6,7,
                          0,3,7,4,
                          1,2,6,5,
                          0,1,2,3,
                          4,5,6,7]
        block_VBO=glGenBuffers(1)
        glBindBuffer(GL_ARRAY_BUFFER,block_VBO)
        a=numpy.array(block_point_buffer,dtype='float32')
        glBufferData(GL_ARRAY_BUFFER,sys.getsizeof(a),a,GL_STATIC_DRAW)
        block_EBO=glGenBuffers(1)
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,block_EBO)
        a=numpy.array(block_EBO_buffer,dtype='float32')
        glBufferData(GL_ELEMENT_ARRAY_BUFFER,sys.getsizeof(a),a,GL_STATIC_DRAW)
        block_EBO_buffer_len=len(a)
        block_VAO=glGenVertexArrays(1)
        glBindVertexArray(block_VAO)
        glBindBuffer(GL_ARRAY_BUFFER,block_VBO)
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,block_EBO)
        glVertexPointer(3,GL_FLOAT,0,None)
        glEnableClientState(GL_VERTEX_ARRAY)
        glBindVertexArray(0)
        draw=True
    glBindVertexArray(block_VAO)
    glDrawElements(GL_QUADS,block_EBO_buffer_len,GL_UNSIGNED_INT,None)
    glBindVertexArray(0)

print_blocks is in the mainloop. If I use glBegin and glEnd, it can be drawn normally.But after I use VBO, no graphics will be displayed. I don't want to use shaders, I don't need them.Also, how can I bind colors array to VAO?

Rabbid76 · Accepted Answer · 2021-12-25T08:46:55.810

1

The type of the indices in the element buffer needs to be integral. It has to match the type specified in the draw call (GL_UNSIGNED_INT ):

~~a=numpy.array(block_EBO_buffer,dtype='float32')~~

a= numpy.array(block_EBO_buffer, dtype = 'uint32')

edited Dec 25 '21 at 08:46

answered Dec 25 '21 at 08:27

Rabbid76

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Your answer is useful,thank you very much.But also,how can I bind colors array to VAO? – Wzq Dec 25 '21 at 17:19
@Wzq Create a VBO for the colors (`color_VBO`) with RGBA colors. And then `glBindBuffer(GL_ARRAY_BUFFER,color_VBO)` `glColorPointer(4,GL_FLOAT,0,None)` `glEnableClientState(GL_COLOR_ARRAY)`. Note, `glColorPointer`, `glVertexPointer`, etc. associates the currently bound array buffer object to the attribute. – Rabbid76 Dec 25 '21 at 17:29

OpenGL VBO can run without error but no graphics

1 Answers1