Developer Tip: Adjust prop animation speed

While in Oshkosh, Hal mentioned to me a problem that a friend of his was having with regards to the speed props animate in FSX. He asked what the equivalent adjustment in FSX is to the prop_anim_ratio value that used to work in FS9. Unfortunately, prop_anim_ratio does not work in FSX. I was determined to get to the root of what controls this for FSX so I started digging into modeldef.xml and this is what I found:

  <!– prop codes will need to be re-implemented (will also need proper simvar) –>
    <PartInfo>
        <Name>prop_anim</Name>
        <AnimLength>100</AnimLength>
        <Animation>
            <Parameter>
                <Sim>
                    <Variable>PROP ROTATION ANGLE:1</Variable>
                    <Units>percent</Units>
                    <Bias>0</Bias>
                    <Scale>0.1592</Scale>
                </Sim>
            </Parameter>
        </Animation>
    </PartInfo>

    <PartInfo>
    <Name>prop0_still</Name>
    <Copy>prop_anim</Copy>
    <AnimLength>100</AnimLength>
    <Visibility>
      <Parameter>
        <Code>
          (A:PROP MAX RPM PERCENT:1, percent) 6.25 &lt; if{ 1 } els{ 0 }
        </Code>
      </Parameter>
    </Visibility>
    <Animation>
      <Parameter>
        <Sim>
          <Variable>PROP ROTATION ANGLE:1</Variable>
        </Sim>
      </Parameter>
    </Animation>
  </PartInfo>

First of all, the note above about the prop codes needing to be re-implemented tells me that this code is work-in-progress, and hopefully will be better in the next version of FS. That being said, adjustments can be made to obtain desired results. Notice how in the part prop0_still the prop_anim is copied. This told me that each prop animation is rooted in the behavior of prop_anim. So, looking at the prop_anim code, the only "variable" I see is:

<Scale>0.1592</Scale>

I began to experiment with this value and successfully change the animations of the props! In FS9, an aircraft with full mixture, full prop, and full power shows a prop disc that is barely in motion, essentially moving so fast it doesn’t appear that it is moving. I cannot get the exact same results with changing the scale value, but I have been able to slow the disc down significantly with all levers firewalled. I get optimum results using a value of 0.0530. I recommend experimenting for yourself to obtain the animation speeds you desire.

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2 Comments

Filed under Flight Simulator

2 responses to “Developer Tip: Adjust prop animation speed

  1. Brian

    That\’s why you\’re the king, Owen

  2. Jean-Robert Turcot

    Wow !
    This is what I was looking and hoping for…
    Merci beaucoup !

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