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FSX random virble for gauges

T

tomerh

Messages
118
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israel
Hi

I just work on precision panel for C172P/S

I just add some Random fluctuations to VOR needles (depande on VHF Reception range) and some other gauges.

I just add sone formulas to the (A:NAV1 CDI, number):

<Macro Name="random1">
(E:Local time, seconds) 2 * sin 3 *
</Macro>

<Macro Name="random2">
(E:Local time, seconds) 0.5 * cos 4 *
</Macro>

<Macro Name="random3">
(E:Local time, seconds) 3 * cos -1.5 *
</Macro>

<Macro Name="random">
@random1 @random2 @random3 (A:NAV1 HAS NAV, bool) * * *
</Macro>

this creates a number thats runs between -11 to +11 almost random

I have 2 questions:

1) do you think this formulas can caouse memory leak and stutters, do you know better formula for random movenent in and out?

2) do elements that are not visible (with <Visible> tag) affects on sim performance?
 
Hi thanks for answering I will try this random formula.

my main quwestion is if formula depands on sim time thats runs always, can cause performance hit, like stutters...

p.s what is the meaning of <update> ?
 
I have had a need for an XML random number generator for some time now. Could never see a reliable way of implementing it myself. This Pierre L'Ecuyer style one came along at a very opportune moment. I have incorporated it already and it works just fine. Thanks a lot, Bob! :)
 
tomerh said:
Hi thanks for answering I will try this random formula.

my main quwestion is if formula depands on sim time thats runs always, can cause performance hit, like stutters...

p.s what is the meaning of <update> ?
Click to expand...


update

Definition: bring up to date
Synonyms: amend, modernize, refresh, refurbish, rejuvenate, renew, renovate, restore, revise
 
In the case of XML, it is a section where you would place stuff you want to be evaluated every gauge cycle (up to 18 times per second).

Code: 
<Update>
   (* stuff to be evaluated/executed every cycle *)
</Update>
 
tomerh said:
Hi thanks for answering I will try this random formula.

my main quwestion is if formula depands on sim time thats runs always, can cause performance hit, like stutters...

p.s what is the meaning of <update> ?
Click to expand...
I don't believe that using an xml sim variable (A:, E:, P: ) will have more impact on performance than using an L: variable.
Not 100% sure, but I believe the variable is calculated/stored by FS anyways every cycle, so memory usage/calculation time for updating the variable should be the same whether you use it or not (?)

I'm using the following quasirandom number generator based on middle square method suggested by John Von Neumann. While said to be a very poor generator, if it was good enough for him working on Eniac, it's good enough for me on FS :D
http://en.wikipedia.org/wiki/Middle-square_method
Code: 
(L:RandomNumber,number) 
(E:ABSOLUTE TIME,seconds) 1 % + 
d * 100 * 1 % 
(>L:RandomNumber,number)
 
Hi

I finnished to build my VOR gauge which considerate the VHF range formula (line of site).
when flying at low altitude and far from VOR station, the signal we can receive is on and off, cause the needle to rotate randomally left and right, also the to/from flag moves on and off untill we climb to altitude witch the signal is high enough for a stable indication.

the problem is when the random formula takes action on the VOR needle, I get light performance hit.

I done a test:
default VOR
my VOR but not tuned to a station (no random)
my VOR tuned to a station (with random)
the results is -11% frame rate hits and some stutters

in my opinion this performance hit is too high for some real gimics :)

if you want to test my VOR gauge, just download from
http://www.virtual-flight.com/dl/fsx/vor.zip and use vor!VOR1_Indicator ...



my question about <update> is:
if I want only one element to update at 5 HZ
I need to use it like this?

<update frequncy="5">
<element>

</element>
</update>

or

<element>
<update frequncy="5">

</update>
</element>

?

Thanks

Tomer
 
tomerh said:
Hi

I finnished to build my VOR gauge which considerate the VHF range formula (line of site).
when flying at low altitude and far from VOR station, the signal we can receive is on and off, cause the needle to rotate randomally left and right, also the to/from flag moves on and off untill we climb to altitude witch the signal is high enough for a stable indication.

the problem is when the random formula takes action on the VOR needle, I get light performance hit.

I done a test:
default VOR
my VOR but not tuned to a station (no random)
my VOR tuned to a station (with random)
the results is -11% frame rate hits and some stutters

in my opinion this performance hit is too high for some real gimics :)

if you want to test my VOR gauge, just download from
http://www.virtual-flight.com/dl/fsx/vor.zip and use vor!VOR1_Indicator ...



my question about <update> is:
if I want only one element to update at 5 HZ
I need to use it like this?

<update frequncy="5">
<element>

</element>
</update>

or

<element>
<update frequncy="5">

</update>
</element>

?

Thanks

Tomer
Click to expand...

Some GOOD news ?
I don't think the "random" behaviour of your VOR Gauges is very "Real World" Realistic.

The VOR gauge's FLAG has a far degree of Hystresis. Once you climb high enough for the flag to indicate you have enough signal for a reliable bearing reading, then the signal has to drop quite significantly again, before the flag goes back to indicating "No signal".

It would be very rare to see a VOR gauge acting the way you describe.

You might do better to simulate this Hystresis effect , and gain the added advantage, of not needing to process the Frame rate reducing code you currently have added.

Note: While better than nothing, the line of sight equation does NOT take into account terrain.
(Adding the effect of terrain is not an insignificant task)

While the addition of line of sight range is neat, it is only a first approximation to what is really happening, so it really does not have to be that exacting.
 
Last edited:
hi Geoff,

you right, I fly c172 in real world and I know that line of sight range is only formula. what happand in real word in depand on terrain and temerature, atmoshper and meny parameters.

but in FSX thare is no "line of sight". almost all VHF VOR and UHF DME range is ~150 NM, so I want to simulate real behavior of VOR/DME from takeoff to cruise alt.

about the Hystresis effect formula:
I'll try to reduce the speed of Hystresis effect but I guess that the fps drop will be the same if I still use (E:Local time, seconds) :mad:.

here is video I taked from my last flight.
http://www.youtube.com/watch?v=cqV0jV8M1G8

we can see during takeoff roll, the needle with light Hystresis around center and off flag.
between 150ft to 250ft, on and off and above 250ft, albost stable neddle and flag with light Hystresis
 
Last edited:
tomerh said:
I have 2 questions:

1) do you think this formulas can caouse memory leak and stutters, do you know better formula for random movenent in and out?

2) do elements that are not visible (with <Visible> tag) affects on sim performance?
Click to expand...


1) No, they can't cause memory leaks and stutters other than those produced by the normal rendering of the gauge. In your VOR's example, it shouldn't be any difference because the code is very simple.

2) Yes, and it can be easily measured: Put yourself in VC main view, with the whole panel visible, check FPS value, then scroll down the view until it shows only the floor of the cockpit and check FPS again; the difference would be produced by a rendering of the panel's gaugeset.

teson1 said:
I don't believe that using an xml sim variable (A:, E:, P: ) will have more impact on performance than using an L: variable.
Not 100% sure, but I believe the variable is calculated/stored by FS anyways every cycle, so memory usage/calculation time for updating the variable should be the same whether you use it or not (?)
Click to expand...

Sim variables (A:,E:,etc) are always updated at standard frame rate, whether they are used in a gauge or not. Local (L) variables are updated/recalled only when they are referenced within a gauge's code.

tomerh said:
my question about <update> is:
if I want only one element to update at 5 HZ
I need to use it like this?

<update frequncy="5">
<element>

</element>
</update>

or

<element>
<update frequncy="5">

</update>
</element>

?

Thanks
Click to expand...

<Update> must go outside an <Element> structure. For example:

Code: 
<Gauge xxx>
  <Update Frequency="5"/>
  <Element1>
  </Element1>
  <Element2>
  </Element2>
  etc
</Gauge>
Tom
 
tomerh said:
hi Geoff,

you right, I fly c172 in real world and I know that line of sight range is only formula. what happand in real word in depand on terrain and temerature, atmoshper and meny parameters.

but in FSX thare is no "line of sight". almost all VHF VOR and UHF DME range is ~150 NM, so I want to simulate real behavior of VOR/DME from takeoff to cruise alt.
Click to expand...

What I would suggest is this.

Calculate the line of sight range (LOS Range), at the most, once a second.
Set your own Flag, with Hystresis
ie if ((Range > LOS Range) and (flag == 0)) then Flag = 1
if ((Range < (0.9 * LOS Range)) and (flag ==1 )) then Flag = 0

Then, if Flag =1, you are out of range of VOR.
( Force Flag indiactor to show, and Center needle)

No need for and Random calculations, or any random needle movements.
 
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