Living without zoom…

by David Burnett • Wednesday March 19th, 2008
Posted in Oxidizer Blog, Using Oxidizer

This is going to cover ground similar to Scott’s blog on Scale and Zoom
but it’s going to come at it from a different angle.

Scale and Zoom do very similar things, they both zoom in on the flame, however there is one very big difference. Zoom increases the quality to ‘make up ‘ for the zooming in, which increases render time, exponentially.

For the math inclined hiding in the comments of Scott’s article is this little formula

quality -> quality * (2 ^ zoom) * (2 ^ zoom)

so for the less math inclined…

  • a zoom of 1 multiplies the quality by 4 (2^1 = 2)
  • a zoom of 2 multiplies the quality by 16 (2^2 = 4)
  • a zoom of 3 multiplies the quality by 64 (2^3 = 8)

Now I’m sure you’re wondering how this effects the render times. Render time is more or less a linear function of quality. Again for the non math folks that means doubling the quality with double the render times, tripling will triple the render times etc. That means…

  • a zoom of 1 multiplies the render time by 4
  • a zoom of 2 multiplies the render time by 16
  • a zoom of 3 multiplies the render time by 64

Lets look if that holds up in real life.

quality zoom time increase
500 0 2.96
1000 0 5.62 x 1.9
2000 0 10.85 x 3.6
4000 0 21.46 x 7.25
 
4000 0 21.46
4000 1 85.47 x 4.0
4000 2 338.21 x 15.8
4000 3 1357.22 x 63.2

I think that’s close enough.

I called this post living without Zoom because I wanted to suggest that keeping Zoom at 0 is an practical option and may even be useful.So what is useful in this context, well I think it comes down to two things

  1. More control over render times
  2. Ease of use

Where do I see those advantages coming from?

  • The effect on render time of increasing the quality is more predictable.
  • You do not end up trying to juggle three parameters to get the quality and area of the flame you want.

For example, that final render’s parameters are equivalent to a quality setting of 4000 x 64 = 256,000. I wonder how much you could reduce it and not tell the difference, or still have an acceptable image quality. I’d guess you could use a quality setting of 128,000 and the scale adjusted to match. I’m sure you’d notice the halving of the render times and what’s more you’d know that is roughly what you’d get. Perhaps you need something in the middle of those two values, what exactly would you need to change the zoom and scale by to get that same image quality. Of course you could still adjust the quality to 3000, but you might not have such a nice round figure to work with. Along the same lines, reducing the zoom down by 0.5 would reduce the render time by..erm…anyone..??

One last note before I throw the floor open to comments, I’ve told you how zoom affects quality, you might not know how it affects the scale.

scale = scale * 2^zoom

So zoom effectively multiples the scale by the square of the zoom. A zoom of 1 doubles the scale, 2 quadruples scale, 3 multiples the scale by 8. So if you have a scale of 100 and a zoom of 2, you can change the zoom to 0 and alter the zoom to 400 to get the same area of the flame.



2 Comments

  1. Scott Chitwood
         March 24, 2008

    Whew! It’s been a crazy month for me — little time for my Mac (or creativity) these past few weeks, hopefully that’ll change real soon. I guess the good side is I’ve had a fair amount of time to chew on this idea.

    I’ll be the first to raise my hand and say the math ideas are sometimes way over my head, so taking time to read and digest this stuff is a big benefit to understanding Oxidizer a bit better. The next step is to actually to try “living without zoom” on some of my future renders. Thanks for pushing us along David!

  2. ekdor
         October 11, 2009

    I also tend to think visually. Could I request an example?

    Cheers,.

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