Having empty space at the start of an animation produces unexpected
results.
void Animation::add_keyframe(const Time::TimeDelta &t, const RefPtr<const KeyFrame> &kf, float ss, float es)
{
void Animation::add_keyframe(const Time::TimeDelta &t, const RefPtr<const KeyFrame> &kf, float ss, float es)
{
+ if(keyframes.empty() && t!=Time::zero)
+ throw invalid_argument("Animation::add_keyframe");
if(!keyframes.empty() && t<keyframes.back().time)
throw invalid_argument("Animation::add_keyframe");
if(!keyframes.empty() && t<keyframes.back().time)
throw invalid_argument("Animation::add_keyframe");