4.7 How to use OpenGL Shader Language feature of OpenGL 2 based on GLEW?

  In SOL2.0.48 ,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 OpenGLRenderContex class are 3 and 1 respectively. You can also specify those versions in the the file 'oglprofile.ogl' file in the following way.

// ContextVersion
// oglversion.ogl
majorVersion = 3
minorVersion = 0

 OpenGLObject
OpenGLProgram
OpenGLRenderContext
OpenGLVertexAttribute
OpenGLShader
OpenGLFragmentShader
OpenGLVertexShader
 The following is a very simple sample program to use OpenGLProram, OpenGLFragmentShader, and OpenGLVertexShader, and OpenGLVertexAttribute 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.



/*
 * MultiColoredTriangleShader.cpp 
 * Copyright (c) 2015 Antillia.com TOSHIYUKI ARAI. ALL RIGHTS RESERVED. 
 */


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

#include <sol/opengl/OpenGLVertex3.h>
#include <sol/opengl/OpenGLClientState.h>

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

#include "Resource.h"

namespace SOL {

class MainView :public OpenGLMainView {

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

public:
  virtual void display()
  {
    if (gc && 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, CountOf(triangles));
          
        buffer.unbind();
          
      } catch (Exception& ex) {
        caught(ex);
      }
    }
  }
 
  virtual void resize(int w, int h)
  {
    if (w == 0 || h == 0) {
      return;
    }
    if (gc) {
      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 = new OpenGLGC();
    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) {
      caught(ex);
    }
  }

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

    ~SimpleView()
    {
    }
  };
  //Inner class ends.
  
private:
  SmartPtr<SimpleView> view;    
  long size(Event& event)
  {
    int w, h;
    event.getSize(w, h);
    if (view) {
      view -> reshape(10, 10, w-20, h-20);
      view -> postResizeRequest(w-20, h-20);
    }
    return 1L;
  }

public:
  MainView(Application& applet, const char* name, Args& args)
  :OpenGLMainView(applet, name, args) 
  {
    Args ar;
    view = new SimpleView(this, "", ar);
  }

  ~MainView()
  {
  }
};
}

//
void Main(int argc, char** argv) 
{
  try {    
    const char*  name = appName(argv[0]);
    Application 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) {
    caught(ex);
  }
}

//fragmentShader.glsl
varying vec3 f_color;
void main(void) {
  gl_FragColor = vec4(f_color.x, f_color.y, f_color.z, 1.0);
}

//vertexShader.glsl
attribute vec2 coord2d;
attribute vec3 v_color;
varying vec3 f_color;
void main(void) {
gl_Position = vec4(coord2d, 0.0, 1.0); f_color = v_color;< }

 Last modified: 8 Dec 2016

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