CTween.h

#ifndef CTWEEN_H
#define CTWEEN_H

#define funcsmoothstart 0
#define funcsmoothstop 1
#define funcsmoothstartflip 3
#define funcsmoothstopflip 4
#define funcsmoothstep 5
#define funcarchstep 6

struct CTweenInfo
{
	float val;
	float ticks;
	float maxticks;
	float inc;
	bool active;
	int func;
	int id;
	float funcval;
	float multiplier;
};

void initialize_CTweenInfo(CTweenInfo *TweenInfo)
{
	TweenInfo->val = 0.0;
	TweenInfo->ticks = 0.0;
	TweenInfo->maxticks = 0.0;
	TweenInfo->inc = 0.0;
	TweenInfo->active = false;
	TweenInfo->func = funcsmoothstart;
	TweenInfo->id = -1;
	TweenInfo->funcval = 0.0;
	TweenInfo->multiplier = 0.0;
}

float smoothstart2(float val)
{
	return val*val;
}

float smoothstop2(float val)
{
	return 1-((1-val)*(1-val));
}

float smoothstartflip2(float val)
{
	return 1 - smoothstart2(val);
}

float smoothstopflip2(float val)
{
	return 1 - smoothstop2(val);
}

float mix(float val1, float val2, float blendval)
{
	return (1-blendval)*val1 + blendval*val2;
}

float smoothstep3(float val)
{
	return mix(smoothstart2(val), smoothstop2(val), val);
}

float arch(float val)
{
	return 4*(val)*(1-val);
}

float tweencalcstepinc(float seconds, float FPS)
{
	return 1/ (FPS * seconds);
}

float tweencalcmaxticks(float seconds, float FPS)
{
	return seconds * FPS;
}

void setTweenInfo(CTweenInfo* tween, int id, float duration, int tweenfunc, float multiplier, bool active, float FPS)
{
	tween->maxticks = tweencalcmaxticks(duration, FPS);
	tween->ticks = 0;
	tween->inc = tweencalcstepinc(duration, FPS);
	tween->multiplier = multiplier;
	tween->val = 0;
	tween->func = tweenfunc;
	tween->funcval = 0;
	tween->active = active;
	tween->id = id;
}

void updateTween(CTweenInfo* tween)
{
	if (tween->active)
	{
		if (tween->ticks < tween->maxticks)
		{
			tween->ticks += 1;
			tween->val += tween->inc;
			switch(tween->func)
			{
				case funcsmoothstart:
					tween->funcval = smoothstart2(tween->val) * tween->multiplier;
					break;
				case funcsmoothstop:
					tween->funcval = smoothstop2(tween->val) * tween->multiplier;
					break;
				case funcsmoothstartflip:
					tween->funcval = smoothstartflip2(tween->val) * tween->multiplier;
					break;
				case funcsmoothstopflip:
					tween->funcval = smoothstopflip2(tween->val) * tween->multiplier;
					break;
				case funcsmoothstep:
					tween->funcval = smoothstep3(tween->val) * tween->multiplier;
					break;
				case funcarchstep:
					tween->funcval = arch(smoothstep3(tween->val)) * tween->multiplier;
					break;
			}
		}
		else
			tween->active = false;
	}
}

#endif