CreateSphereVertices_part.cs

// 半径
float r = size * 0.5f;
int cnt = 0;
int vertCount = divideX * (divideY - 1) + 2;
var vertices = new Vector3[vertCount];

// 中心角
float centerRadianX = 2f * Mathf.PI / (float) divideX;
float centerRadianY = 2f * Mathf.PI / (float) divideY;

// 天面
vertices[cnt++] = new Vector3(0, r, 0);
for (int vy = 0; vy < divideY - 1; vy++)
{
    var yRadian = (float) (vy + 1) * centerRadianY / 2f;

    // 1辺の長さ
    var tmpLen = Mathf.Abs(Mathf.Sin(yRadian));

    var y = Mathf.Cos(yRadian);
    for (int vx = 0; vx < divideX; vx++)
    {
        var pos = new Vector3(
            tmpLen * Mathf.Sin((float) vx * centerRadianX),
            y,
            tmpLen * Mathf.Cos((float) vx * centerRadianX)
        );
        // サイズ反映
        vertices[cnt++] = pos * r;
    }
}

// 底面
vertices[cnt] = new Vector3(0, -r, 0);