Creating a 3D sphere in Opengl using Visual C

Question

I am not able to create a simple 3D sphere using the OpenGL library function glutSolidSphere   in C     Here s what I tried    include lt GL glu h gt   void display           glClear GL COLOR BUFFER BIT        glColor3f 1 0 0 0 0 0        glLoadIdentity         glutSolidSphere  5 0  20 0  20 0        glFlush         void myInit          glClearColor 1 0 1 0 1 0 1 0        glColor3f 1 0 0 0 0 0        glMatrixMode GL PROJECTION        glLoadIdentity         gluOrtho2D 0 0 499 0 0 0 499 0        glMatrixMode GL MODELVIEW        void main int argc char   argv          qobj   gluNewQuadric         glutInit  amp argc argv        glutInitDisplayMode GLUT SINGLE GLUT RGB        glutInitWindowSize 500 500        glutCreateWindow  pendulum                 glutDisplayFunc display        myInit         glutMainLoop

User · Answer

I don t understand how can datenwolf s index generation can be correct  But still I find his solution rather clear  This is what I get after some thinking   inline void push indices vector lt GLushort gt  amp  indices  int sectors  int r  int s        int curRow   r   sectors      int nextRow    r 1    sectors       indices push back curRow   s       indices push back nextRow   s       indices push back nextRow    s 1         indices push back curRow   s       indices push back nextRow    s 1        indices push back curRow    s 1       void createSphere vector lt vec3 gt  amp  vertices  vector lt GLushort gt  amp  indices  vector lt vec2 gt  amp  texcoords               float radius  unsigned int rings  unsigned int sectors        float const R   1   float  rings-1       float const S   1   float  sectors-1        for int r   0  r  lt  rings    r            for int s   0  s  lt  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                 texcoords push back vec2 s S  r R                vertices push back vec3 x y z    radius               push indices indices  sectors  r  s

User · Answer

It doesn t seem like anyone so far has addressed the actual problem with your original code  so I thought I would do that even though the question is quite old at this point   The problem originally had to do with the projection in relation to the radius and position of the sphere  I think you ll find that the problem isn t too complicated  The program actually works correctly  it s just that what is being drawn is very hard to see   First  an orthogonal projection was created using the call  gluOrtho2D 0 0  499 0  0 0  499 0     which  is equivalent to calling glOrtho with near   -1 and far   1   This means that the viewing frustum has a depth of 2  So a sphere with a radius of anything greater than 1  diameter   2  will not fit entirely within the viewing frustum   Then the calls  glLoadIdentity    glutSolidSphere 5 0  20 0  20 0     are used  which loads the identity matrix of the model-view matrix and then   r enders a sphere centered at the modeling coordinates origin of the specified radius   Meaning  the sphere is rendered at the origin   x  y  z     0  0  0   and with a radius of 5   Now  the issue is three-fold    Since the window is 500x500 pixels and the width and height of the viewing frustum is almost 500  499 0   the small radius of the sphere  5 0  makes its projected area only slightly over one fiftieth  2 5 499  of the size of the window in each dimension  This means that the apparent size of the sphere would be roughly 1 2 500th  actually pi 5 2 499 2  which is closer to about 1 3170th  of the entire window  so it might be difficult to see  This is assuming the entire circle is drawn within the area of the window  It is not  however  as we will see in point 2  Since the viewing frustum has it s left plane at x   0 and bottom plane at y   0  the sphere will be rendered with its geometric center in the very bottom left corner of the window so that only one quadrant of the projected sphere will be visible  This means that what would be seen is even smaller  about 1 10 000th  actually pi 5 2  4 499 2   which is closer to 1 12 682nd  of the window size  This would make it even more difficult to see  Especially since the sphere is rendered so close to the edges corner of the screen where you might not think to look  Since the depth of the viewing frustum is significantly smaller than the diameter of the sphere  less than half   only a sliver of the sphere will be within the viewing frustum  rendering only that part  So you will get more like a hollow circle on the screen than a solid sphere circle  As it happens  the thickness of that sliver might represent less than 1 pixel on the screen which means we might even see nothing on the screen  even if part of the sphere is indeed within the viewing frustum    The solution is simply to change the viewing frustum and radius of the sphere  For instance   gluOrtho2D -5 0  5 0  -5 0  5 0   glutSolidSphere 5 0  20  20     renders the following image     As you can see  only a small part is visible around the  equator   of the sphere with a radius of 5   I changed the projection to fill the window with the sphere   Another example   gluOrtho2D -1 1  1 1  -1 1  1 1   glutSolidSphere 1 1  20  20     renders the following image     The image above shows more of the sphere inside of the viewing frustum  but still the sphere is 0 2 depth units larger than the viewing frustum  As you can see  the  ice caps  of the sphere are missing  both the north and the south  So  if we want the entire sphere to fit within the viewing frustum which has depth 2  we must make the radius less than or equal to 1   gluOrtho2D -1 0  1 0  -1 0  1 0   glutSolidSphere 1 0  20  20     renders the following image     I hope this has helped someone  Take care

User · Answer

Datanewolf s code is ALMOST right   I had to reverse both the winding and the normals to make it work properly with the fixed pipeline   The below works correctly with cull on or off for me   std  vector lt GLfloat gt  vertices  std  vector lt GLfloat gt  normals  std  vector lt GLfloat gt  texcoords  std  vector lt GLushort gt  indices   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 lt GLfloat gt   iterator v   vertices begin    std  vector lt GLfloat gt   iterator n   normals begin    std  vector lt GLfloat gt   iterator t   texcoords begin    for r   0  r  lt  rings  r    for s   0  s  lt  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   radius       v     y   radius       v     z   radius        n     -x       n     -y       n     -z     indices resize rings   sectors   4   std  vector lt GLushort gt   iterator i   indices begin    for r   0  r  lt  rings-1  r        for s   0  s  lt  sectors-1  s                          i     r   sectors   s           i     r   sectors    s 1            i      r 1    sectors    s 1            i      r 1    sectors   s                       i      r 1    sectors   s            i      r 1    sectors    s 1            i     r   sectors    s 1             i     r   sectors   s       Edit   There was a question on how to draw this    in my code I encapsulate these values in a G3DModel class   This is my code to setup the frame  draw the model  and end it   void GraphicsProvider3DPriv  BeginFrame  const          int win width          int win height    framework of choice here         glfwGetWindowSize window   amp win width   amp win height      retrieve window         float const win aspect    float win width    float win height             set lighting         glEnable GL LIGHTING           glEnable GL LIGHT0           glEnable GL DEPTH TEST           GLfloat lightpos      0  0 0  0  0            glLightfv GL LIGHT0  GL POSITION  lightpos           GLfloat lmodel ambient       0 2  0 2  0 2  1 0            glLightModelfv GL LIGHT MODEL AMBIENT  lmodel ambient           glLightModeli GL LIGHT MODEL TWO SIDE  GL TRUE              set up world transform         glClearColor 0 f  0 f  0 f  1 f           glClear GL COLOR BUFFER BIT GL DEPTH BUFFER BIT GL STENCIL BUFFER BIT GL ACCUM BUFFER BIT           glMatrixMode GL PROJECTION           glLoadIdentity             gluPerspective 45  win aspect  1  10            glMatrixMode GL MODELVIEW                void GraphicsProvider3DPriv  DrawModel const G3DModel  model  const Transform3D transform const          G3DModelPriv  privModel    G3DModelPriv   model          glPushMatrix            glLoadMatrixf transform GetOGLData              glEnableClientState GL VERTEX ARRAY           glEnableClientState GL NORMAL ARRAY           glEnableClientState GL TEXTURE COORD ARRAY            glVertexPointer 3  GL FLOAT  0   amp privModel- gt vertices 0            glNormalPointer GL FLOAT  0   amp privModel- gt normals 0            glTexCoordPointer 2  GL FLOAT  0   amp privModel- gt texcoords 0             glEnable GL TEXTURE 2D             glFrontFace GL CCW           glEnable GL CULL FACE           glActiveTexture GL TEXTURE0           glBindTexture GL TEXTURE 2D  privModel- gt texname            glDrawElements GL QUADS  privModel- gt indices size    GL UNSIGNED SHORT   amp privModel- gt indices 0            glPopMatrix            glDisable GL TEXTURE 2D               void GraphicsProvider3DPriv  EndFrame  const             Swap front and back buffers            glDisable GL LIGHTING           glDisable GL LIGHT0           glDisable GL CULL FACE           glfwSwapBuffers window               Poll for and process events            glfwPollEvents

User · Answer

Here s the code   glPushMatrix    glTranslatef 18 2 0   glRotatef angle  0  0  0 7   glColor3ub 0 255 255   glutWireSphere 3 10 10   glPopMatrix

User · Answer

In OpenGL you don t create objects  you just draw them  Once they are drawn  OpenGL no longer cares about what geometry you sent it   glutSolidSphere is just sending drawing commands to OpenGL  However there s nothing special in and about it  And since it s tied to GLUT I d not use it  Instead  if you really need some sphere in your code  how about create if for yourself    define  USE MATH DEFINES  include  lt GL gl h gt   include  lt GL glu h gt   include  lt vector gt   include  lt cmath gt      your framework of choice here  class SolidSphere   protected      std  vector lt GLfloat gt  vertices      std  vector lt GLfloat gt  normals      std  vector lt GLfloat gt  texcoords      std  vector lt GLushort gt  indices   public      SolidSphere float radius  unsigned int rings  unsigned int sectors                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 lt GLfloat gt   iterator v   vertices begin            std  vector lt GLfloat gt   iterator n   normals begin            std  vector lt GLfloat gt   iterator t   texcoords begin            for r   0  r  lt  rings  r    for s   0  s  lt  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   radius                   v     y   radius                   v     z   radius                    n     x                   n     y                   n     z                     indices resize rings   sectors   4           std  vector lt GLushort gt   iterator i   indices begin            for r   0  r  lt  rings  r    for s   0  s  lt  sectors  s                       i     r   sectors   s                   i     r   sectors    s 1                    i      r 1    sectors    s 1                    i      r 1    sectors   s                       void draw GLfloat x  GLfloat y  GLfloat z                glMatrixMode GL MODELVIEW           glPushMatrix            glTranslatef x y z            glEnableClientState GL VERTEX ARRAY           glEnableClientState GL NORMAL ARRAY           glEnableClientState GL TEXTURE COORD ARRAY            glVertexPointer 3  GL FLOAT  0   amp vertices 0            glNormalPointer GL FLOAT  0   amp normals 0            glTexCoordPointer 2  GL FLOAT  0   amp texcoords 0            glDrawElements GL QUADS  indices size    GL UNSIGNED SHORT   amp indices 0            glPopMatrix              SolidSphere sphere 1  12  24    void display         int const win width            retrieve window dimensions from     int const win height           framework of choice here     float const win aspect    float win width    float win height       glViewport 0  0  win width  win height        glClear GL COLOR BUFFER BIT   GL DEPTH BUFFER BIT        glMatrixMode GL PROJECTION       glLoadIdentity        gluPerspective 45  win aspect  1  10        glMatrixMode GL MODELVIEW       glLoadIdentity      ifdef DRAW WIREFRAME     glPolygonMode GL FRONT AND BACK  GL LINE    endif     sphere draw 0  0  -5        swapBuffers       int main int argc  char  argv             initialize and register your framework of choice here     return 0

User · Answer

I like the answer of coin  It s simple to understand and works with triangles  However the indexes of his program are sometimes over the bounds  So I post here his code with two tiny corrections   inline void push indices vector lt GLushort gt  amp  indices  int sectors  int r  int s        int curRow   r   sectors      int nextRow    r 1    sectors      int nextS    s 1    sectors       indices push back curRow   s       indices push back nextRow   s       indices push back nextRow   nextS        indices push back curRow   s       indices push back nextRow   nextS       indices push back curRow   nextS      void createSphere vector lt vec3 gt  amp  vertices  vector lt GLushort gt  amp  indices  vector lt vec2 gt  amp  texcoords                    float radius  unsigned int rings  unsigned int sectors        float const R   1   float  rings-1       float const S   1   float  sectors-1        for int r   0  r  lt  rings    r            for int s   0  s  lt  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                 texcoords push back vec2 s S  r R                vertices push back vec3 x y z    radius               if r  lt  rings-1                  push indices indices  sectors  r  s

[c++] Creating a 3D sphere in Opengl using Visual C++

Examples related to c++

Examples related to opengl