#!/usr/bin/env fish

# settings:
set step 0.002		# power increase for each frame
set start 1			# starting power
set end 3			# end power

# internal vars:
set counter 1		# internal counter for numbering images
set pos "$start"	# current power	

# render a frame. power is $argv[1] and counter is $argv[2]
function render
	./march.out $argv[1] "out/3/"(num $argv[2])".bmp" > /dev/null
end

# pad counter with zeroes to the left
function num
	printf "%05i" $argv[1]
end

# iterate over all frames and draw them
while test "$pos" -lt "$end"
	render "$pos" "$counter"
	set pos (math "$pos" + "$step")
	set counter (math $counter + 1)
	set percent (math "ceil((($pos - $start) / ($end - $start)) * 100)")
	echo -ne "\r$percent% ($start -> $pos -> $end)            "
end

echo to convert the frames to a video, use ffmpeg like this: 
echo ffmpeg -r 60 -f image2 -s 1080x1080 -i %05d.bmp -vcodec h264 -crf 20 animation.mp4
echo 
echo explanation:
echo "    -r 60         60 fps output video"
echo "    -s 1080x1080  video resolution"
echo "    -i %u5d.bmp   file name format"
echo "    -vcoded h264  video codec"
echo "    -crf 20       quality. 25 is best, 15 is pretty bad"