This article presents a set of helper classes that encapsulates OpenGL handling and really makes the programmer's life easier (and happier).
This piece of code was originally been written by W.Weyna 'Voytec'. All I did was to publish it to CodeProject.
Here are the main features of the package:
CWGL is a Windows OpenGL rendering interface class. This header defines also a few interfacing wgl_ inlines.
The idea behind the CWGL is to make use of OpenGL in Microsoft Windows as simple as possible.
Under Windows only one OpenGL rendering context may be active in a single thread. CWGL helps you write a single threaded Windows application which need more than one OpenGL rendering context.
CWGL's default one.
wgl.Begin(&windowOrBitmapDC);
wgl.End();
// CView.h CWGL m_wgl;
// CView.cpp CView::OnDraw(pDC) { m_wgl.Begin(pDC); glClearColor(1.0, 1.0, 1.0, 0.0); glClear(GL_COLOR_BUFFER_BIT); m_wgl.End(); }
CRGBSurface tmpSurf; // CRGBSurface encapsulates a DIB section GDI object tmpSurf.Create(10, 10); CWGL wgl; wgl.Begin(tmpSurf.GetDC()); glClearColor(1.0, 1.0, 1.0, 0.0) glClear(GL_COLOR_BUFFER_BIT); wgl.End(); tmpSurf.CopyToClipboard();
CWGL objects are used, but remember that only one RC can be created for one window. wgl1.Begin(&windowDC);
{
CWGL wgl2;
wgl2.Begin(&bitmapDC);
wgl2.End();
// here wgl2 destructor delete's wgl2 RC and makes
// wgl1 RC current again.
}
// here all the display lists and textures of wgl1 RC
// remain valid
wgl1.End();
wgl.Begin() with no DC to make last used RC of this window current again. wgl.Begin(&windowDC); wgl.End(); ... // some time in the future... wgl.Begin(); wgl.End();
CWGL::End() you may ask what the rendering time was with GetRenderingTime(). When rendering on different DIB sections or bitmaps, a new RC with PFD_DRAW_TO_BITMAP pixelformat is always created for that bitmap.
WindowsNT: CWGL synchronizes GDI and OpenGL access to rendering surface automatically.
When switching RC's of different pixelformats with CWGL, all textures and display lists must be recreated in a new RC. Display list sharing is possible when RCs are of the same pixelformat (this means also that you cannot share between window and bitmap RC).
Please also note that under Windows, only one RC may be created for a given window and this RC cannot be used for another window.
CGLTexture is a simple wrapper to OpenGL texture object. It enables easy changing of texture images, reusing existing texture object when possible.
ChangeImage to create/recreate/reuse a texture and copy CGLImage image to the texture object.
Bind() to bind a texture.
Invalidate() before switching to a new RC. If Invalidate() is called and then Bind() is called in a new RC, the texture will be automatically recreated using a backup copy of the image.
ChangeImage() with second parameter set to false so it won't make unnecessary backup copy of the image. if(bChangeImage) { // Handle a request to use a different image // for texture. bChangeImage = false; CGLImage glImage; glImage.Create(m_strNewImageFilePath, GL_RGBA); m_tex1.ChangeImage(&glImage, false); } m_tex1.Bind();
Coordn() function to generate texture coordinates which point to the four corners of current subimage inside a possibly larger texture. glBegin(GL_QUADS); m_tex1.Coord0(); glVertex3f(-5.0, -5.0, 0.0); m_tex1.Coord1(); glVertex3f(-5.0, 5.0, 0.0); m_tex1.Coord2(); glVertex3f(5.0, 5.0, 0.0); m_tex1.Coord3(); glVertex3f(5.0, -5.0, 0.0); glEnd(); glFlush(); glDisable(GL_TEXTURE_2D);
A documentation of the classes has been generated and is available with the source code distribution.
#include "OGLT.h"
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