How can I stack opengl shapes into std::vector - c++

Question

How can I stack up these two opengl shapes into a container class?
can someone please show me
I wont mind a template.
void myTriangle()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glTranslatef(-1.5f,0.0f,-6.0f);
glBegin(GL_TRIANGLES);
glColor3f(1.0f,0.0f,0.0f);
glVertex3f( 0.0f, 1.0f, 0.0f);
glColor3f(0.0f,1.0f,0.0f);
glVertex3f(-1.0f,-1.0f, 0.0f);
glColor3f(0.0f,0.0f,1.0f);
glVertex3f( 1.0f,-1.0f, 0.0f);
glEnd();
glutSwapBuffers ( );
}
void myQuad()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glColor3f(0.5f,0.5f,1.0f);
glBegin(GL_QUADS);
glVertex3f(-1.0f, 1.0f, 0.0f);
glVertex3f( 1.0f, 1.0f, 0.0f);
glVertex3f( 1.0f,-1.0f, 0.0f);
glVertex3f(-1.0f,-1.0f, 0.0f);
glEnd();
glutSwapBuffers ( );
}

Answer 1

not really sure of what you want to do, but you can do:
typedef void (*ShapeFct_t)();
typedef std::vector<ShapeFct_t> ShapeArray_t;
ShapeArray_t shapes;
shapes.push_back(myTriangle);
shapes.push_back(myQuad);

Answer 2

You can define a Shape base class, and have Quad and Triangle inherit from that class with an overloaded draw function. Here's a simplified, incomplete example:
/* Define these; use tuples, your own class, 3rd party, whatever */
class Position;
class Color;
/* Shape class is abstract base class */
class Shape {
public:
Shape(const Position &pos) : position(pos) {}
virtual void draw() = 0;
protected:
Position position;
};
/* Triangle and Quad classes are Shapes */
class Triangle : public Shape {
public:
Triangle(const Position &pos,
const Position &p1, const Color &c1,
const Position &p2, const Color &c2,
const Position &p3, const Color &c3)
: Shape(pos),
pos1(p1), col1(c1),
pos2(p2), col2(c2),
pos3(p3), col3(c3)
{}
virtual void draw() {
glTranslatef(position.x, position.y, position.z);
glBegin(GL_TRIANGLES);
glColor3f(col1.r, col1.g, col1.b);
glVertex3f(pos1.x, pos1.y, pos1.z);
glColor3f(col2.r, col2.g, col2.b);
glVertex3f(pos2.x, pos2.y, pos2.z);
glColor3f(col3.r, col3.g, col3.b);
glVertex3f(pos3.x, pos3.y, pos3.z);
glEnd();
}
private:
Position pos1, pos2, pos3;
Color col1, col2, col3;
};
class Quad : public Shape {
/* Your implementation here */
};
void draw_all_shapes() {
std::vector<Shape*> shapes;
shapes.push_back(new Triangle(Position(-1.5f, 0f, -6f),
Position(0f, 1f, 0f), Color(1f, 0f, 0f),
Position(-1f, -1f, 0f), Color(0f, 1f, 0f),
Position(0f, 0f, 1f), Color(0f, 0f, 1f)));
shapes.push_back(new Quad(/* Arguments */));
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
for(auto it = shapes.begin(); it != shapes.end(); it++) {
(*it)->draw();
}
glutSwapBuffers();
}
Note: As I said, the example is incomplete. It's also untested and a little bit messy (memory leaks and such) but those problems are out of the scope of this question. The main point I am trying to demonstrate here is that you can convert your functions to classes, which can leverage inheritance and polymorphism to simplify your code.

Answer 3

Not sure if you care to edit what the shape looks like after you create it but you could put it in a display list, then store each display list in whatever container you like:
GLuint triangleList = glGenLists(1);
glNewList(triangleList, GL_COMPILE);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glTranslatef(-1.5f,0.0f,-6.0f);
glBegin(GL_TRIANGLES);
glColor3f(1.0f,0.0f,0.0f);
glVertex3f( 0.0f, 1.0f, 0.0f);
glColor3f(0.0f,1.0f,0.0f);
glVertex3f(-1.0f,-1.0f, 0.0f);
glColor3f(0.0f,0.0f,1.0f);
glVertex3f( 1.0f,-1.0f, 0.0f);
glEnd();
glEndList();
GLuint quadList = glGenList(1);
glNewList(quadList, GL_COMPILE);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glColor3f(0.5f,0.5f,1.0f);
glBegin(GL_QUADS);
glVertex3f(-1.0f, 1.0f, 0.0f);
glVertex3f( 1.0f, 1.0f, 0.0f);
glVertex3f( 1.0f,-1.0f, 0.0f);
glVertex3f(-1.0f,-1.0f, 0.0f);
glEnd();
glEndList();
At this point you can store the quadList and triangleList in whatever container you like. You can tell OpenGL to display them by using the glCallList() function. To delete the list call glDeleteList().