function calc_fade_progress(t, transition_start, transition_end)
local tt = (t - transition_start) / (transition_end - transition_start)
if tt < 0.0 then
- tt = 0.0
+ return 0.0
elseif tt > 1.0 then
- tt = 1.0
+ return 1.0
end
-- Make the fade look maybe a tad more natural, by pumping it