2d Sprite Speed

You might want to change how you calculate the speed of objects. Instead of using how often you update per second, you should use a typical unit of speed: distance/time. Typically, I you could use pixels/second. For large world with their own world coordinates, it should be your world unit/seconds.

This way you would use the delta time since the last update, and figure out where the objects move based o it's current velocity. For example, assuming using World Coordinates:


// This assume the ScreenEntity class has an X and Y velocity, as well as an X and Y location.
class ScreenEntity
{
...
private:
double XVelocity;
double YVelocity;
double XLocation;
double YLocation;

Sprite *EntitySprite;
...
};

void ScreenEntity::UpdateAndDraw(double TimeSinceLastUpdate)
{
double ScreenX;
double ScreenY;

// Move this object based on it's current velocity
XLocation += XVelocity * TimeSinceLastUpdate;
YLocation += YVelocity * TimeSinceLastUpdate;

// Draw it at the current screen Coordinates, ScreenX and ScreenY must be passed by reference
// This function knows where the camera is in the world, and can give you screen Coordinates for this object
ConvertWorldCoordsToScreen(XLocation, YLocation, ScreenX, ScreenY);

Sprite->Draw(ScreenX, ScreenY);


You would call this function every loop, and pass in the time difference since the last call. This way, you only have to set the X and Y Velocity, and your object will move each time you call this. Give it a big positive X Velocity, and it will move faster to the right. Give it a small negative X, and it will move slow to the left.

Hope that helps!