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Machine independent render times

Friday, April 18th, 2008 | Author:

Asked about render times of the transparency samples, Matt answered with this:

Render times were about 3 hours (on one core) for each of the latest two renders, on computers which render Karsten’s TG2 benchmark in about 5 or 6 minutes.
(source: Matt at the Planetside-forum)

This gave me the idea to use Karsten’s benchmark table to define a new measure for render times that allows for fast comparison of the time it takes to render a specific scene – even if you don’t know the speed of the machine it was rendered on.

I hereby define the unit “relative render time” in short RRT. The formula is simple:

RRT = render time * index.

Where index is the value from the benchmarks in points. So, if you take the render time in minutes, the unit for the relative render time is p*min.

Now if you want to tell your reader how long a scene took to render, you can just give him the RRT. No matter on which machine you render the file – the RRT stays the same. If a someone uses RTT as a measure, you can immediately calculate how long your own pc would take to compute the same image

render time in minutes = RRT / index

.. and all this without having to ask for the specifications of the system that was used to render it originally, let alone having to estimate how much faster or slower one’s own machine is in comparison. The index value is doing that for us.

Example

When we read Matt’s statement above we wonder: 3h.. is that a lot… or very little? How long would that take on my pc?

  • Matt didn’t specify the RTT directly, so we have to quickly calculate it ourselves. To do this, we take a look at Karsten’s benchmark table. There we can see that 5 to 6 minutes corresponds to an index value of about 78 points. For 3h = 3*60min = 180min the formula yields

    RRT = 180min * 78p = 14040 p*min

  • Now we use the second formula:

    RRT / index = render time in minutes

    and insert the index of our machine. Let’s assume our pc has a Core 2 Duo 6300 processor. We take a look at the benchmark table and find an index value of 95 points. All we have to do now is calculate:

    14040 p*min / 95p = 148min = 2.46h

    So this render would take about 2.5h on our machine.

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