§ 15

Render time for a sequence

How long does it take to render the sequence, and how much time can each frame take at most?

Answer: Before you send a shot to rendering you should know whether it can be finished in time. Render one test frame in final resolution and quality and time it. The calculator multiplies it up to the whole sequence divides by number of machines in render farm and tells how long each frame must take at most if it's to make the deadline. The competence goal on rendering and render optimisation is precisely that trade-off.

Formula

Frames = længde (s) × billedhastighed

Maskintid = frames × rendertid pr. frame

Rendertid på vægur = maskintid ÷ antal maskiner (forudsat at frames fordeles jævnt)

Højeste tid pr. frame = timer til deadline × 60 × maskiner ÷ frames

Symbols and units in the formula
Symbol	Meaning	Unit
varighed_sek	Sequence length	s
fps	Frame rate	fps
min_pr_frame	Render time per frame (measured on a test frame)	min
maskiner	Number of machines rendering simultaneously	maskiner
timer_til_deadline	Hours until deadline	timer
=	Render time (wall clock)	timer
=	Number of frames	frames
=	Total machine time	timer
=	Maximum per frame to meet deadline	min

Validity and source

Source: Frames × render time per frame ÷ number of machines

Does not apply when

The test frame should be one of the heavy ones: with most motion blur, most lights and most simulation in the image. Time to load the scene per job, compositing and new rendering after corrections are additional, so plan with some slack.

Worked example

The calculator's own default values inserted. The figures are calculated with exactly the formula the tool uses.

Substituted

Sequence length30 s
Frame rate24 fps
Render time per frame (measured on a test frame)4 min
Number of machines rendering simultaneously1 maskiner
Hours until deadline48 timer

Giver

Render time (wall clock)48.0 timer
Number of frames720 frames
Total machine time48.0 timer
Maximum per frame to meet deadline4.00 min

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Sådan bruger du den

Før et shot eller en hel film sendes til rendering, skal du vide, om den kan blive færdig til deadline. Render en tung testframe, og lad beregneren gange op til hele sekvensen og fordele på maskinerne. Den viser også, hvor lang tid en frame højst må tage.

Step by step

Render én tung testframe i endelig opløsning og kvalitet, og noter tiden.
Skriv sekvensens længde og billedhastighed.
Gang antal frames med tiden pr. frame, og del med antal maskiner.
Sammenlign med tiden til deadline. Er den for lang, så sænk samples, brug denoiser eller del passes op.

Typical errors

At måle på en let frame i starten af shottet. Brug den tungeste.
At glemme passes og AOV'er, der renderes for sig.
At regne uden tid til en ny rendering efter kundens rettelser.

Examples from everyday life

Produktanimation på én pc

En produktanimation af en høretelefon på 30 sekunder i 24 fps renderes i Cycles på din egen pc. En testframe tager 4 minutter, og kunden skal have filmen om 48 timer.

Sequence length: 30 s
Frame rate: 24 fps (film)
Render time per frame (measured on a test frame): 4 min
Number of machines rendering simultaneously: 1 machines
Hours until deadline: 48 hours

It means: Det giver 720 frames og en rendertid på 48 hours. En frame må højst tage 4 min, så der er ingen luft til rettelser.

Samme shot på fire maskiner

Studiet sætter fire maskiner på samme job.

Sequence length: 30 s
Frame rate: 24 fps (film)
Render time per frame (measured on a test frame): 4 min
Number of machines rendering simultaneously: 4 machines
Hours until deadline: 48 hours

It means: Rendertiden falder til 12 hours, og en frame må nu tage op til 16 min. Maskintiden er stadig 48 hours.

Kortfilm på renderfarm

En kortfilm på 5 minutter i 25 fps tager 12 minutter pr. frame og skal renderes på 20 noder i en renderfarm over en weekend på 60 timer.

Sequence length: 300 s
Frame rate: 25 fps (European TV)
Render time per frame (measured on a test frame): 12 min
Number of machines rendering simultaneously: 20 machines
Hours until deadline: 60 hours

It means: Filmen er 7,500 frames og tager 75 hours at rendere, men for at nå weekenden må en frame højst tage 9.6 min. Sænk samples, brug denoiser eller få flere noder.

Rule of thumb

1 sekund i 24 fps med 1 minut pr. frame tager 24 minutter.

How to check the answer

Rendertid × maskiner skal give maskintiden.