Hey all,

Having some trouble with what should be a simple thing to do...

I've successfully compiled and linked very simple vertex and fragment shaders.

Having trouble seeing my red triangle though.

This stuff all goes fine:

GLint ProgramObject = glCreateProgram();
glAttachShader ( ProgramObject, VertexShaderObject ); 
glAttachShader ( ProgramObject, PixelShaderObject );
glLinkProgram ( ProgramObject );
glUseProgram ( ProgramObject );

VBO creation:

GLuint vbo;
glGenBuffers ( 1, &vbo );
glBindBuffer ( GL_ARRAY_BUFFER, vbo );
    
GLfloat pos[] = { -0.5, -0.5, 0.5,
                           0.5, -0.5, 0.5,
                           0.0,  0.5, 0.5 };
                                     
glBufferData, GL_ARRAY_BUFFER, sizeof(pos), &pos[0], GL_STATIC_DRAW;

// Something is wrong here i am guessing...

int nPositionID = glGetAttribLocation ( ProgramObject, "s_vPosition" );
glEnableVertexAttribArray ( nPositionID );
glVertexAttribPointer ( nPositionID, 3, GL_FLOAT, FALSE, 0, 0 );
           
   /*
   glBegin(GL_TRIANGLES);
   glVertexAttrib3f ( nPositionID, -0.5, -0.5, 0.0 );  // If i do this, i see my red triangle (correct fragment color).
   glVertexAttrib3f ( nPositionID,  0.5, -0.5, 0.0 );  // Makes me believe context is ok.
   glVertexAttrib3f ( nPositionID,  0.0,  0.5, 0.0 );
   glEnd();
   */
   
glDrawArrays ( GL_TRIANGLES, 0, 3 );
    
SwapBuffers ( m_DeviceContext );

vertex shader looks like this:

#version 130\n
in vec4 s_vPosition;
void main()
{
gl_Position = vec4 ( s_vPosition.x, s_vPosition.y, s_vPosition.z, 1.0 );
}

Any ideas?

I just started this shader stuff, but I think your vertex shader needs to output a color to the fragment shader.

OpenGL by default looks down the -z axis. Setting your triangle z coords to -1 should help

GLfloat pos[] = { -0.5, -0.5, -1.0,
                           0.5, -0.5, -1.0,
                           0.0,  0.5, -1.0 };

Actually the OpenGL clip space is from -1 to 1 so 0.5 should be ok. One problem could be, that in the shader you specify the position as a 4 component vector, whereas you only hand in 3 component vectors with glVertexAttribPointer.

Also make sure you disabled the depth test.

Argh it wasn't any of those things :(

Any other ideas?

It looks like your vertices are not been transform by any perspective nor ortho matrix.

It looks like your vertices are not been transform by any perspective nor ortho matrix.

        glewInit();


        const char *vertexShader ="#version 130\n"
                "in vec3 s_vPosition;"
                "void main()"
                "{"
                "    gl_Position = vec4 ( s_vPosition.x, s_vPosition.y, s_vPosition.z, 1.0 );"
                "}";

        const char *pixelShader ="#version 130\n"
                "void main()"
                "{"
                "    gl_FragColor = vec4(1.0, 0.0, 0.0, 0.0);"
                "}";


        GLint VertexShaderObject = glCreateShader(GL_VERTEX_SHADER);
        glShaderSource(VertexShaderObject, 1, &vertexShader, NULL);
        glCompileShader(VertexShaderObject);

        GLint PixelShaderObject = glCreateShader(GL_FRAGMENT_SHADER);
        glShaderSource(PixelShaderObject, 1, &pixelShader, NULL);
        glCompileShader(PixelShaderObject);

        GLint ProgramObject = glCreateProgram();
        glAttachShader ( ProgramObject, VertexShaderObject );
        glAttachShader ( ProgramObject, PixelShaderObject );
        glLinkProgram ( ProgramObject );

        int success;
        glGetProgramiv(ProgramObject, GL_LINK_STATUS, &success);
        if (success != GL_TRUE)
            std::cout << "Linking failed!" << std::endl;


        GLuint vbo;
        glGenBuffers ( 1, &vbo );
        glBindBuffer ( GL_ARRAY_BUFFER, vbo );

        GLfloat pos[] = { -0.5, -0.5, 0.5,
                                   0.5, -0.5, 0.5,
                                   0.0,  0.5, 0.5 };

        glBufferData(GL_ARRAY_BUFFER, sizeof(pos), &pos[0], GL_STATIC_DRAW);

        while (!window.getState().shutdown) {

            glClear(GL_COLOR_BUFFER_BIT);

            glDisable(GL_DEPTH_TEST);
            glUseProgram ( ProgramObject );
            int nPositionID = glGetAttribLocation ( ProgramObject, "s_vPosition" );

            glBindBuffer ( GL_ARRAY_BUFFER, vbo );
            glEnableVertexAttribArray ( nPositionID );
            glVertexAttribPointer ( nPositionID, 3, GL_FLOAT, GL_FALSE, 0, 0 );

            glDrawArrays ( GL_TRIANGLES, 0, 3 );


            Engine::Platform::BaseWindow::Event event;
            while (window.getNextEvent(event)) {
            }
            window.getContext()->swap();
        }