3.3.18 MultiColoredTriangleShader

  In OZ++2.0.23, we have updated our OpenGL C++ classes to use GLEW in order to create a context-version-dependent context, and to use the features of OpenGL Shader Language.   Currently, the default major version and the minor version for OpenGLContex class are 2 and 1 respectively.
  The following is a very simple sample program to use OpenGLProram, OpenGLFragmentShader, and OpenGLVertexShader classes to draw a multicolored triangle. In this program, the sources for FragmentShader and VertexShader are defined in the files of "fragmentShader.glsl" and "vertexShader.glsl" respectively.
Please note that you can specify a major version and a minor version for OpenGLContext on the command line in the following way:

%opengl2/./MultiColoredTriangleShader major=2 minor=1

However, if you would like to use default versions, you can omit the version options on the command line:

%opengl2/./MultiColoredTriangleShader

As shown below, you may fail to create a context of versions major=3 and minor=1 with X Error: GLXBadFBConfig, depending on your OpenGL/Mesa version.



  The compile method of OpenGLShader class shows a message to standard output stream when it detects a compile error, as shown bellow.







//
//MultiColoredTriangleShader.cpp
//Copyright (c) 2016 Antillia.com TOSHIYUKI ARAI. ALL RIGHTS RESERVED.

#include <oz++/opengl/OpenGLMainView.h>
#include <oz++/opengl/OpenGLView.h>
#include <oz++/opengl/OpenGLGC.h>
#include <oz++/opengl/OpenGLArrayBuffer.h>

#include <oz++/opengl/OpenGLVertex3.h>
#include <oz++/opengl/OpenGLClientState.h>

#include <oz++/opengl2/OpenGLVertexShader.h>
#include <oz++/opengl2/OpenGLFragmentShader.h>
#include <oz++/opengl2/OpenGLProgram.h>
#include <oz++/opengl2/OpenGLVertexAttribute.h>
#include <oz++/opengl2/OpenGLUniform.h>


namespace OZ {

class MainView :public OpenGLMainView {

private:
  //Inner class starts.
  class SimpleView: public OpenGLView {
  private:
    OpenGLGC gc;
    SmartPtr<OpenGLProgram>    program;

public:
  virtual void display()
  {
    if (program) {
      gc.clear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
      gc.loadIdentity();
      gc.clearColor(1.0f, 1.0f, 1.0f, 1.0f);
      
      try {
        program -> use();
    
        OpenGLClientState clientState(GL_VERTEX_ARRAY);
        
        struct Coord2Color3 {
          GLfloat coord[2];
          GLfloat color[3];
        };
        Coord2Color3 triangles[] = {
          {{ 0.0,  0.5},  { 1.0, 1.0, 0.0}},
          {{-0.5, -0.5},  { 0.0, 0.0, 1.0}},
          {{ 0.5, -0.5},  { 1.0, 0.0, 0.0}},
        };
        
        OpenGLArrayBuffer buffer;
        buffer.bind();
        buffer.data(sizeof(triangles), triangles, GL_STATIC_DRAW);

 
        OpenGLVertexAttribute coord(program->getAttributeLocation("coord2d"));
        OpenGLVertexAttribute vcolor(program->getAttributeLocation("v_color"));
        coord.setPointer(2, GL_FLOAT, GL_FALSE, sizeof(Coord2Color3), 0); 
        
        vcolor.setPointer(3, GL_FLOAT, GL_FALSE,  sizeof(Coord2Color3), (GLvoid*) (2 * sizeof(GLfloat)) );

        gc.drawArrays(GL_TRIANGLES, 0, SizeOf(triangles));
          
        buffer.unbind();
          
      } catch (Exception& ex) {
        ex.display();
      }
    }
  }
 
  virtual void resize(int w, int h)
  {
    if (w == 0 || h == 0) {
      return;
    }
    gc.matrixMode(GL_PROJECTION);
    gc.loadIdentity();
    gc.perspective(16.0, (double)w / (double)h, 0.5, 40.0); 

    gc.matrixMode(GL_MODELVIEW);
  }

  virtual void initialize()
  {
    gc.matrixMode(GL_PROJECTION);
    gc.loadIdentity();

    gc.enable( GL_DEPTH_TEST );
    gc.frustum(1 , -1 , -1 , 1 , 1 , 10);
    
    try { 
      OpenGLVertexShader vertexShader("vertexShader.glsl");
      
      OpenGLFragmentShader fragmentShader("fragmentShader.glsl");      
      
      program = new OpenGLProgram();
      program -> attachShader(vertexShader);
      program -> attachShader(fragmentShader);

      program -> link();
      
      program -> detachShader(vertexShader);
      program -> detachShader(fragmentShader);
      
    } catch (Exception& ex) {
      ex.display();      
    }
  }

  public:
    SimpleView(OpenGLMainView* parent, const char* name, Args& args)
    :OpenGLView(parent, name, args)
    {
    } 

    ~SimpleView()
    {
    }
  };
  //Inner class ends.
  
private:
  SmartPtr<SimpleView>  view;

public:
  MainView(OpenGLApplication& applet, const char* name, Args& args)
  :OpenGLMainView(applet, name, args) 
  {
    Args ar;
    ar.set(XmNopenGLBufferType, (XtArgVal)getBufferType());
    view = new SimpleView(this, "", ar);
  }

  ~MainView()
  {
  }
};
}

//
int main(int argc, char** argv) 
{
  try {    
    const char*  name = argv[0];
    OpenGLApplication applet(name, argc, argv);

    Args args;
    args.set(XmNwidth,  480);
    args.set(XmNheight, 400);
    
    MainView view(applet, name, args);
    view.realize();

    applet.run();
    
  } catch (Exception& ex) {
    ex.display();
  }
  return 0;
}



Last modified: 1 Jan 2017

 Last modified: 1 Jan 2017

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