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Author Topic: Help required  (Read 6533 times)

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slibenli

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Re: Help required
« Reply #12 on: August 10, 2019, 04:05:31 PM »





This reminds me of the ready room in old Flight Unlimited :)

(skip to 4:15)

[FAC]Ghost129er

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Re: Help required
« Reply #13 on: August 10, 2019, 04:24:10 PM »

No way!!! I have Flight Unlimited 2 on a disk which a real pilot gave to me as he knew my obsession and love for planes! I've got such a cheeky and cheesy grin you have no idea, love the SAS community and the common sims a lot of us have had! (sorry for the derail).
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Pursuivant

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Re: Help required
« Reply #14 on: August 13, 2019, 09:49:31 AM »

This is a quick and dirty .jpg of the map, based on two screenshots edited together. Sadly, the resolution of the original isn't quite good enough to determine the exact map number (in lower L hand corner just below the map itself).

I'm not sure of the original source, but the "Secret" marking means that it was a wartime issue map.



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Pursuivant

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Re: Help required
« Reply #15 on: August 18, 2019, 03:00:49 AM »

A bit more research on my part.

Each sector and subsector had its own control station with customized tabletop-sized maps in the operations room for the filterers and plotters. Overall command was at Bentley Priory, now a museum with a recreated filtering room with giant map. Each subsector appears to have had its own custom map, loosely based on a map similar to what I posted above.

Wikipedia has a great picture of a sector fighter control map here, from RAF Uxbridge:

https://upload.wikimedia.org/wikipedia/commons/b/bf/Plotting_Table.jpg

The search term "operations room" + map gets a lot of other good pictures as well.
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Stainless

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Re: Help required
« Reply #16 on: August 18, 2019, 04:36:08 AM »

That image is my main reference.

I have already started putting together assets, but getting the map sorted is a skull crusher.




These will be added to my noew deferred renderer so we can have real lighting effects for the squadron status.
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Stainless

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Re: Help required
« Reply #17 on: September 03, 2019, 02:08:20 AM »

I have decided that the only way to solve this problem is to write a tool.

So I have started a map creator.

It takes GIS data as input and can create maps of any region of the world in any projection. So we know that during WWII the allies used a Cassini projection for all the maps. I can add that as well as any others we need.

Then you can set a visualisation theme to match the maps used by any country.

Add any locations or other GIS data you want to have visible on the map

And render it to a file.

You can obviously do any tweaks you want after that in any art package you like.

Eventually I want to add the ability to take other input data as well, so you could render maps of airfields or towns or anything really as long as you have data for it.


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Stainless

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Re: Help required
« Reply #18 on: September 03, 2019, 02:11:28 AM »

I do need help with something else though.

At the moment I have a problem with my lighting.

I calculate the suns position based on time, date, latitude, longitude. So at night the sun is still there, it's just below the horizon.

I need an equation that defines when the sun goes below the horizon based on aircraft altitude.

Aircraft high in the sky are lit for longer than aircraft at low altitude.

I need to model that as well

If anyone spots an equation for this, please post a link here as I am really busy at the moment.

Cheers guys
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Pursuivant

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Re: Help required
« Reply #19 on: September 04, 2019, 02:06:13 PM »

My apologies if I'm missing something, but can't you determine illumination of aircraft above the horizon in the same way you determined the illumination of the moon and planets by the sun using the Pythagorean Theorem or Secant-Tangent Theorem and the object's azimuth?

Darkness/gloaming occurs on the planet's surface when the earth's motion takes the line formed by the sun's top edge and the true horizon beyond the observer's position, but only ceases to illuminate objects as higher altitudes when the planet's motion brings the sun's position below the object's astronomical horizon as compared to the true horizon. The same illumination effect allows mountains to remain illuminated after the rest of the terrain goes dark.

Basic calculations here:

https://en.wikipedia.org/wiki/Horizon

If you want to get into the nuances of atmospheric refraction, the necessary calcs are here:

https://aty.sdsu.edu/explain/atmos_refr/altitudes.html

If you want to simplify it, define levels of illumination for civil twilight, nautical twilight, astronomic twilight, and night based on each 6 degrees the sun goes below the horizon.

https://www.timeanddate.com/astronomy/astronomical-twilight.html
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Stainless

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Re: Help required
« Reply #20 on: September 05, 2019, 12:38:05 AM »

I will read through those, they seem to be exactly what I need.

It's not a trivial problem for two reasons.

1) Coordinate systems
    The Earth, Sun and Moon are in Galactic coordinates. The renderer works in world coordinates.  Conversion between the two is possible, but floating point accuracy makes the results unreliable.
2) Screen positions
    I don't render the sun as a 2D object, it exists in the shaders as a calculated angular position which is then subject to display transformations.

So the two simple, obvious approaches just fail to work.

Thanks for digging those references out for me, I will dig through them and see what I can do

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slibenli

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Re: Help required
« Reply #21 on: September 05, 2019, 01:15:14 AM »

Assuming that the object position, earth center and sun direction are available in the shader, you could cast a ray from the object into the sun's direction and test whether it intersects the earth's sphere.

https://gitlab.com/vrresto/render_util/blob/master/shaders/util.glsl#L62

Stainless

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Re: Help required
« Reply #22 on: September 05, 2019, 12:19:46 PM »

Tried that , didn't work. don't know why, I think it is just a matter of scale.

I have a prototype solution which is hard to explain,,  of course

SO .....

It is easy to calculate the distance to the horizon based on altitude.

So I know one point and a distance.

I then calculate the two intersection points of two circles.

One with the aircraft at the centre and radius (distance to the horizon), and the other the Earth.

From one of these intersection points I can calculate a direction from the horizon to the aircraft.

I can then calculate the "elevation" of this direction and compare it with the suns elevation (already known)

I haven't put it into the renderer yet, just ran the maths for a few values, but it looks like it should work.


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Stainless

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Re: Help required
« Reply #23 on: September 05, 2019, 12:57:35 PM »

It works !!!!!!!!!!!!


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