Why do you think that requires virtual lookup? Virtual lookup is for runtime decisions.

Which API does this use:

class CircleRenderer {
public:
     Renderer();
     ~Renderer();

     void begin();
     void circle(float x, float y, float r);
     void end();
private:
     // Omitted...
};

What client changes are required if the implementation was switched from/to OpenGL/Direct3D/Software?

: Wrong tags

Why do you think that requires virtual lookup? Virtual lookup is for runtime decisions.

Which API does this use:

class CircleRenderer {
public:
     Renderer();
     ~Renderer();

     void begin();
     void circle(float x, float y, float r);
     void end();
private:
     // Omitted...
};

What client changes are required if the implementation was switched from/to OpenGL/Direct3D/Software?