Static variables in the scope of a draw function in OpenGL?

Question

As an example, I have the following draw function in some OpenGL application:

void Terrain::Draw(float ox, float oy, float oz) {
    float terrainWidth = stepWidth * (width - 1.0f);
    float terrainLength = stepLength * (length - 1.0f);
    float startWidth = (terrainWidth / 2.0f) - terrainWidth;
    float startLength = (terrainLength / 2.0f) - terrainLength;

        (...)
}

Terrain is a class and I'm sure that the step and terrain width/length instance variables will never change during the lifetime of the object (they are initialized before the first call to the draw function).

Assuming my application runs at a steady 25fps, the function will be called 25 times a second. The values will never change, they will always be the same.

Would I gain anything in declaring those function variables as static? To prevent them from being destroyed and declared every time the function is called?

Answer 1

Would I gain anything in declaring those function variables as static?

it's really a small amount of data: don't bother, unless you have a ton of instances.

To prevent them from being destroyed and declared every time the function is called?

this typically takes the form:

class Terrain { 
public:
    // interface
protected:
    // more stuff
private:
    // ... existing variables
    const float d_terrainWidth;
    const float d_terrainLength;
    const float d_startWidth;
    const float d_startLength;
};

then you can use the precalculated invariants from your Draw implementation.