Script to generate IcoSphere VertexData

IcoSphere.cpp

std::vector<glm::vec3> GenerateIcoSphereVertices(int radius, std::vector<unsigned int>& Indices, int subDivisions /*= 1*/)
{
    const float S_STEP = 186 / 2048.0f;         // horizontal texture step
    const float T_STEP = 322 / 1024.0f;         // vertical texture step
    const float H_ANGLE = M_PI / 180.0f * 72;   // 72 degree = 360 / 5
    const float V_ANGLE = atanf(1.0f / 2);      // elevation = 26.565 degrees

    std::vector<float> baseVertices(12 * 3);    // array of 12 vertices (x,y,z)
    int i1, i2;                                 // indices
    float z,xy;                                 // vertices
    float hAngle1 = -M_PI / 2 - H_ANGLE / 2;    // start from -126 deg at 1st row
    float hAngle2 = -M_PI / 2;                  // start from -90 deg at 2nd row

    // the first top vertex at (0, 0, r)
    baseVertices[0] = 0;
    baseVertices[1] = 0;
    baseVertices[2] = radius;

    // 10 vertices as 1st and 2nd rows
    for (int i = 1; i <= 5; ++i)
    {
        i1 = i * 3;         // index for first row
        i2 = (i + 5) * 3;   // index for 2nd row

        z = radius * sinf(V_ANGLE);
        xy = radius * cosf(V_ANGLE);

        baseVertices[i1] = xy * cosf(hAngle1);      // x
        baseVertices[i2] = xy * cosf(hAngle2);
        baseVertices[i1 + 1] = xy * sinf(hAngle1);  // y
        baseVertices[i2 + 1] = xy * sinf(hAngle2);
        baseVertices[i1 + 2] = z;                   // z
        baseVertices[i2 + 2] = -z;

        // next horizontal angles
       hAngle1 += H_ANGLE;
       hAngle2 += H_ANGLE;
    }
    // the last bottom vertex at (0, 0, -r)
    i1 = 11 * 3;
    baseVertices[i1] = 0;
    baseVertices[i1 + 1] = 0;
    baseVertices[i1 + 2] = -radius;

    // std::vector<glm::vec3> verts;
    // for(int i = 0; i < baseVertices.size(); i += 3)
    // {
    //     verts.push_back(glm::vec3(baseVertices[i], baseVertices[i + 1], baseVertices[i + 2]));
    // }
    // return verts;
    std::vector<glm::vec3> vertices;
    std::vector<glm::vec3> normals;
    std::vector<glm::vec2> uv;
    std::vector<unsigned int> indices;
    vertices.clear();

    float *v0, *v1, *v2, *v3, *v4, *v11;                // vertex positions
    float n[3];                                         // face normal
    float t0[2], t1[2], t2[2], t3[2], t4[2], t11[2];    // texCoords
    unsigned int index = 0;

    v0 = &baseVertices[0];
    v11 = &baseVertices[11 * 3];
    for(int i = 1; i <= 5; ++i)
    {
        v1 = &baseVertices[i * 3];
        if(i < 5)
            v2 = &baseVertices[(i + 1) * 3];
        else
            v2 = &baseVertices[(i + 5) * 3];

        v3 = &baseVertices[(i + 5) * 3];
        if((i + 5) < 10)
            v4 = &baseVertices[(i + 6) * 3];
        else
            v4 = &baseVertices[6 * 3];

        // texture coords
        t0[0] = (2 * i - 1) * S_STEP;   t0[1] = 0;
        t1[0] = (2 * i - 2) * S_STEP;   t1[1] = T_STEP;
        t2[0] = (2 * i - 0) * S_STEP;   t2[1] = T_STEP;
        t3[0] = (2 * i - 1) * S_STEP;   t3[1] = T_STEP * 2;
        t4[0] = (2 * i + 1) * S_STEP;   t4[1] = T_STEP * 2;
        t11[0]= 2 * i * S_STEP;         t11[1]= T_STEP * 3;

        vertices.push_back(glm::vec3(v0[0], v0[1], v0[2]));
        vertices.push_back(glm::vec3(v1[0], v1[1], v1[2]));
        vertices.push_back(glm::vec3(v2[0], v2[1], v2[2]));
        uv.push_back(glm::vec2(t0[0], t0[1]));
        uv.push_back(glm::vec2(t1[0], t2[1]));
        uv.push_back(glm::vec2(t2[0], t2[1]));
        indices.push_back(index);
        indices.push_back(index + 1);
        indices.push_back(index + 2);

        vertices.push_back(glm::vec3(v1[0], v1[1], v1[2]));
        vertices.push_back(glm::vec3(v3[0], v3[1], v3[2]));
        vertices.push_back(glm::vec3(v2[0], v2[1], v2[2]));
        uv.push_back(glm::vec2(t1[0], t1[1]));
        uv.push_back(glm::vec2(t3[0], t3[1]));
        uv.push_back(glm::vec2(t2[0], t2[1]));
        indices.push_back(index + 3);
        indices.push_back(index + 4);
        indices.push_back(index + 5);

        vertices.push_back(glm::vec3(v2[0], v2[1], v2[2]));
        vertices.push_back(glm::vec3(v3[0], v3[1], v3[2]));
        vertices.push_back(glm::vec3(v4[0], v4[1], v4[2]));
        uv.push_back(glm::vec2(t2[0], t2[1]));
        uv.push_back(glm::vec2(t3[0], t3[1]));
        uv.push_back(glm::vec2(t4[0], t4[1]));
        indices.push_back(index + 6);
        indices.push_back(index + 7);
        indices.push_back(index + 8);

        vertices.push_back(glm::vec3(v3[0],  v3[1],  v3[2]));
        vertices.push_back(glm::vec3(v11[0], v11[1], v11[2]));
        vertices.push_back(glm::vec3(v4[0],  v4[1],  v4[2]));
        uv.push_back(glm::vec2(t3[0], t3[1]));
        uv.push_back(glm::vec2(t11[0], t11[1]));
        uv.push_back(glm::vec2(t4[0], t4[1]));
        indices.push_back(index + 9);
        indices.push_back(index + 10);
        indices.push_back(index + 11);

        index += 12;
    }
    Indices = indices;
    return vertices;
}