Programming with Visual Studio
MFC and OpenGL
Outline
• Creating a project
• Adding OpenGL initialization code and
libraries
• Creating a mouse event
• Drawing with OpenGL
• Saving information to use later (Point data)
• Relevant Questions about OpenGL/MFC
Creating a Project in Visual Studio
Creating a Project in Visual Studio
Creating a Project in Visual Studio
Creating a Project in Visual Studio
• Header File – Code that need to be added for
OpenGL
HDC m_hDC;
HGLRC m_hGLContext;
BOOL SetWindowPixelFormat(HDC hDC);
BOOL CreateViewGLContext(HDC hDC);
int m_GLPixelIndex;
afx_msg int OnCreate(LPCREATESTRUCT lpCreateStruct);
afx_msg void OnDestroy();
afx_msg void OnSize(UINT nType, int cx, int cy);
DECLARE_MESSAGE_MAP() //already in .h file
Creating a Project in Visual Studio
• Need to make sure the messages are getting
sent/received - .cpp file
BEGIN_MESSAGE_MAP(CCssample1View, CView)
ON_WM_CREATE()
ON_WM_DESTROY()
ON_WM_SIZE()
// Standard printing commands
ON_COMMAND(ID_FILE_PRINT, CView::OnFilePrint)
ON_COMMAND(ID_FILE_PRINT_DIRECT, CView::OnFilePrint)
ON_COMMAND(ID_FILE_PRINT_PREVIEW, CView::OnFilePrintPreview)
END_MESSAGE_MAP()
Creating a Project in Visual Studio
BOOL CCssample1View::CreateViewGLContext(HDC hDC){
m_hGLContext = wglCreateContext(m_hDC);
if (m_hGLContext == NULL)
return FALSE;
if (wglMakeCurrent(m_hDC, m_hGLContext)==FALSE)
return FALSE;
return TRUE;
}
Creating a Project in Visual Studio
int CCssample1View::OnCreate(LPCREATESTRUCT lpCreateStruct) {
if (CView::OnCreate(lpCreateStruct) == -1)
return -1;
HWND hWnd = GetSafeHwnd();
m_hDC = ::GetDC(hWnd);
if (SetWindowPixelFormat(m_hDC)==FALSE)
return 0;
if (CreateViewGLContext(m_hDC)==FALSE)
return 0;
return 0;
}
Creating a Project in Visual Studio
void CCssample1View::OnDestroy() {
CView::OnDestroy();
if(wglGetCurrentContext()!=NULL) {
// make the rendering context not current
wglMakeCurrent(NULL, NULL) ;
}
if (m_hGLContext!=NULL){
wglDeleteContext(m_hGLContext);
m_hGLContext = NULL;
}
// Now the associated DC can be released.
CView::OnDestroy();
}
Creating a Project in Visual Studio
void CCssample1View::OnSize(UINT nType, int cx, int cy) {
CView::OnSize(nType, cx, cy);
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0, width, 0.0, height);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
// for double buffering
glDrawBuffer(GL_BACK);
}
Creating a Project in Visual Studio
• BOOL CCssample1View::SetWindowPixelFormat(HDC hdc){…}
• This function is pretty big, in the interest of space, here is a
link to a site that shows how it is done. This site also goes over
the stuff mentioned here in more detail about creating the
project.
• http://web.agelid.com/protect/utile/documentation/OpenGL/Example%2
01%20-%20Writing%20an%20OpenGL%20Program.htm
Creating a Project in Visual Studio
• The previously mentioned functions and
variables will allow you to use OpenGL with
your project once they are added.
• This code below must also be added to your
OnDraw function to get the render context.
//openGL code
CRect rcClient;
GetClientRect(rcClient);
Adding OpenGL initialization code
• The following code can be added to your OnDraw
function.
//openGL code
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0, width, 0.0, height);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
Adding OpenGL Libraries
Adding OpenGL Libraries
Adding OpenGL Libraries
Adding OpenGL Libraries (Paths)
Adding OpenGL Libraries (Paths)
Creating a mouse event
• afx_msg void OnLButtonDown(UINT nFlags,
CPoint point); //added to header file
• ON_WM_LBUTTONDOWN() //added to
message map at top of cpp file
• void CCssample1View::OnLButtonDown(UINT
nFlags, CPoint point) {
//code to be exectud when Lbutton is pressed
down
}
Drawing with OpenGL
glBegin(GL_LINES);
glVertex3d(100, height-100, 0);
//height-100 is to make sure point is
actually at 100, 100. It actually starts at bottom left of screen
glVertex3d(200, height-200, 0);
glEnd();
The above code draws a line from coordinates
(100, 100) to (200, 200).
Drawing with OpenGL
• Primitives you can draw with OpenGL
– glBegin(GL_LINES);
– glBegin(GL_POINTS);
– glBegin(GL_TRIANGLES);
– glBegin(GL_LINE_LOOP);
• There are others, these are just a few that you
will most likely use.
Saving info to use later (Point data)
• Suppose we have a right button press event
void CCssample1View::OnRButtonDown(UINT nFlags, CPoint point) {
line savedLine;
savedLine.start = start; //start variable was found with a left button press, save now
savedLine.end = point; //save the point where the right click occurred
savedLinesVector.push_back(savedLine);
//save line into vector
}
//in the header file, in the class itself
struct savedLine{
CPoint start, end;
//Cpoint is mfc defined type
};
vector <savedLine> savedLinesVector; //vector of type savedLine
Saving info to use later (Point data)
for(unsigned i=0; i<savedLinesVector.size(); i++){
//iterate through vector printing lines
glBegin(GL_LINES); //this can be outside for loop also,
depending on what you are doing
glVertex2d(savedLinesVector[i].start.x, savedLinesVector[i].start.y);
glVertex2d(savedLinesVector[i].end.x, savedLinesVector[i].end.y);
glEnd();
} //this will draw all lines to the screen, this is
done in the OnDraw function
Relevant Questions about
OpenGL/MFC
• How do I read pixels from the screen in OpenGL?
– glReadPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format,
GLenum type, GLvoid *data);
– If you wanted to read one pixel at (100, 100):
• glReadPixels(100, 100, 1, 1, GL_RGB, GL_BYTE, data);
• The variable data is where the pixel information is stored
• How do I change the color of pixel(s)?
– glColor3f(1.0, 0.0, 0.0);
//red color
• How do I clear the buffer?
– glClear(GL_COLOR_BUFFER_BIT);
• What is the CPoint type?
– It allows you to gain access to the x, y coordinates at a particular point. Ex:
CPoint p1; // variable p1 of type CPoint
p1.x; //x coordinate at point
p1.y; //y coordinate at point