@Override public void execute( @Nonnull final Element element, final float normalizedTime, @Nullable final Falloff falloff, @Nonnull final NiftyRenderEngine r) { if (interpolator != null) { r.setColorAlpha(interpolator.getValue(normalizedTime)); } else { Alpha a = start.linear(end, normalizedTime); r.setColorAlpha(a.getAlpha()); } }