CODEWITHSUNDEEP
c++opengl
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Reputation: 299

Trouble with OpenGL Vertex Array Sphere C

Heres a pic of the problem:

enter image description here

And here is the wireframe:

wireframe

As you can see from the pictures above, I have some sort of weird graphical issue and am not sure how to fix, I think somethings wrong with the code although noone else has had trouble with the code.

Code:

    unsigned int rings = 12, sectors = 24;

    float const R = 1./(float)(rings-1);
    float const S = 1./(float)(sectors-1);
    int r, s;

    vertices.resize(rings * sectors * 3);
    normals.resize(rings * sectors * 3);
    texcoords.resize(rings * sectors * 2);
    std::vector<GLfloat>::iterator v = vertices.begin();
    std::vector<GLfloat>::iterator n = normals.begin();
    std::vector<GLfloat>::iterator t = texcoords.begin();
    for(r = 0; r < rings; r++) for(s = 0; s < sectors; s++) {
            float const y = sin( -M_PI_2 + M_PI * r * R );
            float const x = cos(2*M_PI * s * S) * sin( M_PI * r * R );
            float const z = sin(2*M_PI * s * S) * sin( M_PI * r * R );

            *t++ = s*S;
            *t++ = r*R;

            *v++ = x * getR();
            *v++ = y * getR();
            *v++ = z * getR();

            *n++ = x;
            *n++ = y;
            *n++ = z;
    }

    indices.resize(rings * sectors * 4);
    std:vector<GLushort>::iterator i = indices.begin();
    for(r = 0; r < rings; r++) for(s = 0; s < sectors; s++) {
            *i++ = r * sectors + s;
            *i++ = r * sectors + (s+1);
            *i++ = (r+1) * sectors + (s+1);
            *i++ = (r+1) * sectors + s;
    }

    glEnableClientState(GL_VERTEX_ARRAY);
    glEnableClientState(GL_NORMAL_ARRAY);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);

    glVertexPointer(3, GL_FLOAT, 0, vertices.data());
    glNormalPointer(GL_FLOAT, 0, normals.data());
    glTexCoordPointer(2, GL_FLOAT, 0, texcoords.data());
    glDrawElements(GL_QUADS, indices.size(), GL_UNSIGNED_SHORT, indices.data());

Code taken from (Creating a 3D sphere in Opengl using Visual C++)

Upvotes: 3

Views: 846

Answers (1)

the_jk
the_jk

Reputation: 599

indices will end up with indexes outside of vertices. The last four values in indices will be:

*i++ = 11 * 24 + 23 = 287;
*i++ = 11 * 24 + (23 + 1) = 288;
*i++ = (11 + 1) * 24 + (23 + 1) = 312;
*i++ = (11 + 1) * 24 + 23 = 311;

but vertices only contains 288 vertexes. I assume why it works for other people is that glDrawElements might wrap the indexes in some implementations.

Upvotes: 4

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