Question

I followed this tutorial and I’m currently trying to create a class to draw cubes. The class populates the buffers in a function called setup and draws them in a function called draw.

There are no errors however nothing is displayed on the screen.

My question is basicly how do I go about making a class from which I can render cubes.

Using Xcode 4.2, Opengl and Objective-C.

[edit]

-(void)SetShader:(GLuint)InShader
{
glUseProgram(InShader);

_positionSlot = glGetAttribLocation(InShader, "Position");
_colorSlot = glGetAttribLocation(InShader, "SourceColor");
glEnableVertexAttribArray(_positionSlot);
glEnableVertexAttribArray(_colorSlot);

_projectionUniform = glGetUniformLocation(InShader, "Projection");
_modelViewUniform = glGetUniformLocation(InShader, "Modelview");

_texCoordSlot = glGetAttribLocation(InShader, "TexCoordIn");
glEnableVertexAttribArray(_texCoordSlot);
_textureUniform = glGetUniformLocation(InShader, "Texture");  
}

-(void)SetupVBO
{
    GLuint vertexBuffer;
    glGenBuffers(1, &vertexBuffer);
    glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(CubeVertices), CubeVertices, GL_STATIC_DRAW);

    GLuint indexBuffer;
    glGenBuffers(1, &indexBuffer);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(CubeIndices), CubeIndices, GL_STATIC_DRAW);
}

-(void)draw
{
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid*) (sizeof(float) * 3));

glVertexAttribPointer(_texCoordSlot, 2, GL_FLOAT, GL_FALSE, 
                      sizeof(Vertex), (GLvoid*) (sizeof(float) * 7));    

glDrawElements(GL_TRIANGLES, sizeof(CubeIndices)/sizeof(CubeIndices[0]), GL_UNSIGNED_BYTE, 0);  
}

-(void)render:(CADisplayLink*)displayLink 
{
glClearColor(0, 0, 0.2, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);

CC3GLMatrix *projection = [CC3GLMatrix matrix];
float h = 4.0f * self.frame.size.height / self.frame.size.width;
[projection populateFromFrustumLeft:-2 andRight:2 andBottom:-h/2 andTop:h/2 andNear:4 andFar:10];
glUniformMatrix4fv(_projectionUniform, 1, 0, projection.glMatrix);

CC3GLMatrix *modelView = [CC3GLMatrix matrix];
[modelView populateFromTranslation:CC3VectorMake(0, 0, -7)];
[modelView translateBy:CC3VectorMake(0,5,0)];
glUniformMatrix4fv(_modelViewUniform, 1, 0, modelView.glMatrix);

glViewport(0, 0, self.frame.size.width, self.frame.size.height);

[m_cube draw];

[_context presentRenderbuffer:GL_RENDERBUFFER];
}

Answer 1

It was as mentioned a problem with the arrangement of my viewport and perspective setups.