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    <p>While I agree with most of the other answers, in your case you don't need the classical factory pattern. As I can see, you want to have a single class which describes a shape with parametric functions for their geometry. You want to provide convenience methods to create those shapes for some special cases, like the "donut". As long as you don't want to make use of any other inheritance features like overloading some methods for special shape types, you can simply drop your other classes like <code>Donut</code> and just use the "maker" functions in your client code.</p> <p>An option to make the code still look more object-oriented (and to keep the subclasses and use their constructors in the client code), you can rewrite the maker functions to initialization functions, as I want to call them. Note that I also introduced a default constructor which we need in the specialized classes:</p> <pre><code>class ParametricShape { func x, y, z; ... public: ParametricShape(); ParametricShape(func x, func y, func z, ...); protected: void initDonutShape(float); }; class Donut : public ParametricShape { public: Donut(float radius) : ParametricShape() // call default constructor of ParametricShape { initDonutShape(radius); // initialize functions for "Donut" } }; </code></pre> <p>Now, implement the <code>initDonutShape</code> method like this:</p> <pre><code>void ParametricShape::initDonutShape(float radius) { // set the parametric functions x = ... y = ... z = ... } </code></pre> <p>rather than returning a new instance of <code>ParametricShape</code>.</p>
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    1. POreuse factory type constructor in subclass
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    1. COOverriding some of the render stuff is exactly what I'm trying to do here, I want it to always be translated a certain way and have a certain texture. Unfortunately this is for a school project and I've been provided with a modelview class I can't change and they made some of this stuff protected/private. Good suggestion on the init functions I'm just going to go that route. Cheers!
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    2. CO@schwiz At the end, this method is very similar to yours, but with the most important change being done: In the constructor of the subclass, the `ParametricShape` instance has already been created (this is because of the inheritance; you can't avoid this). You should only modify this, not throw this away and recreate another one. However, you only need one subclass per special shape type if you want to treat them all differently (one overloaded render method for each type, for example).
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    3. COOne last note: You can also just initialize the parametric functions in the `Donut` constructor. You don't need the init functions at all. However, they are nice if you want to reuse them from type to type, for example to separate geometry from textures and to create a wooden donut + a metal donut. But in this case, give the init methods a meaningful name, e.g. "initDonutGeometry", "initWoodTexture", etc.
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