[WIP] Periscope accurate Field of View (US, IJN, French, British)

[keltos01]

So as not to clog Captscurvy's optimeter thread with my ramblings I have decided to start this thread.

This thread is intended for the betterment of my IJN, British and French scope views, as captscurvy stated a FOV of 32° was required to use his omnimeter, and since I think it is a very nice addition to SH4, I have decided to check that my scopes are compliant with it.


keltos

[keltos01]

It's that parameter, and the stock magnification of 1.0 at low power/4.0 at high power, that gives the stock attack periscope the incorrect 36 degree wide Field of View (38 degree FoV for the 1280x1024 game resolution). captscurvy

@ Keltos, those figures of the Attack Periscope "stock" AngularAngle of 62.4814 are wrong (I mean, they are incorrect if you expect to have a 32 degree Field of View).
so should i set 32° instead ?

also, and i don't remember the exact figure, when at high power (6x for the IJN) the field of view should be in the magnitude of ? 10° only shouldn't it ? how do I get that, or is the FOV divided by the magnification at that level ?

stock obs periscope :
angular angle=62,4814


stock scopes, both observation and attack, have :





IJN scopes have a magnification of
Obs scope : 4.0 x and 1.0 x
attack scope : 4.0 x and 1.0 x (should be 6.0x)
FOV :62,4814° (=angular angle)


British scopes have a magnification of : stock


French scopes have a magnification of
Obs scope : 2.0 x and 1.1 x
attack scope : 6.0 x and 1.1 x
FOV : 32° (=angular angle)

German scopes have a magnification of :

note that the gradings on the scope are for low power (left) and high power (right) right Hitman ?




let's try and do this once and for all !

keltos

[Hitman]

The problem is that you have actually two things to take care of,

1) Camera aperture (The setting in the cameras.dat)

2) Periscope screen in the game

This last one is the graphic you are tweaking, and it will show the correct FOV only as long as you tune it according to the cameras aperture.

Let me explain that:

You have a rounded hole in the middle of the screen, but that hole can be bigger or smaller, you choose how much. If you make it bigger you are actually gaining field of view, so you would then have to tune the cameras.dat accordingly.

What you need to do is:

1) Decide a standard size of the hole, for all your optical views. I have chose 480 pixels in my mods, for example

2) Tweak the cameras.dat so that you set the proper aperture angle to make that 480 pixels correspond to the 32º you want to have

3) Place the reticle markings in the hole in the proper places, with 1 degree spacing in horizontal separation

4) Tweak all the other cameras apertures in cameras.dat to the same one as in your optics, so that the zoom proportions are correct. (Otherwise it could happen that at 6x zoom in your optics you see objects that are apparently only 2x what you see on the bridge)

[keltos01]

let's use the french scope as an example :

I edited the Periscope_Mask_1024.dds file (stock us)

I then scaled the periscope view I had to fit the hole on the screen and redrew the lines and tick marks



the stock's hole is 540 pixels wide as far as I can tell

1) Decide a standard size of the hole, for all your optical views. I have chose 480 pixels in my mods, for example
so mine is like stock : 540 pixels
2) Tweak the cameras.dat so that you set the proper aperture angle to make that 540 pixels correspond to the 32º you want to have
how ?
3) Place the reticle markings in the hole in the proper places, with 1 degree spacing in horizontal separation
I am measuring in pixels..; how do I calculate how many pixels per degree ?

[edit] 480 pixels

240 half

240 = 16°

240/16 = 1 mark every 15 pixels right ?

[edit]




in the french scope view, there is a vertical line 175 pixels from the center with 9 divisions, so one every 19.44 pixels, I chose 19.5, and a zone without marks 95 pixels wide as half the circle is 270 pixels

if the half the view is 16° wide = 270 pixels then 1° =270/16 = 16,875 pixels

so the divisions as shown on the reticle are each 1.15°


4) Tweak all the other cameras apertures in cameras.dat to the same one as in your optics, so that the zoom proportions are correct. (Otherwise it could happen that at 6x zoom in your optics you see objects that are apparently only 2x what you see on the bridge)
?
keltos

[keltos01]

« Quel grossissement as-tu prévus pour les deux périscopes ? Le commandant L'Herminier donne l'info dans son livre pour le Casabianca, comme ils ont contemporains l'un l'autre, je suppose que ça doit être la même chose.

Angle + grossissement cité par L'Herminier : "environ 6° au grossissement 6, 40° au grossissement normal 1.1." »

so it's 6° FOV at 6x zoom and 40° FOV at 1.1x zoom for the french attack periscope

[CapnScurvy]

Hi keltos, I've read your thread and Hitman is correct in his assessment in how to get the proper Field of View size with whatever size periscope view opening you use.

As an example, I'm going to use the known American periscope specs as having a True Field of View of 32 degrees with a low power magnification of 1.5x, the high power magnification of 6.0x.

First the game's Camers.dat parameter of "AngularAngle=62.4814" is influenced by the parameter "Viewport=xxxx". Now, I'll be the first to admit I don't understand this relationship, so being able to give you a math lesson on how the 62.4814 (which in Silent 3ditor states is in degrees) relates to a True Field of View of 36 degrees in-game.... I DON'T KNOW!! But it does. And the FoV is 38 degrees when you use the 1280x1024 game resolution!! I don't know why or how I just know it does.

So you may ask, How do you know what the stock game Field of View is? I've tested for it, and I recommend you do the same.

In order to test the true FoV of the periscope (or any periscope image you may wish to use), you must use the only tool that is available to you and that's the periscopes relative compass bearing. You will also need to have a test background to measure. A group of stationary ships set at about equal distance from a stationary sub will do the trick. Try THIS download called "Optical Test Mission Pack". There is an American mission called "Optical Test Mission" that can be activated through JSGME. When it is installed in-game you will find under the American Quick Mission menu a mission entitled "Test 21". Run the mission and you will find yourself in front of a group of ships that can be measured using the compass bearing of the periscope. I also recommend you activate the second mod in the "Pack" called "Big Bearing Compass for Stock Periscope". This will give you a much larger compass to read exactly what degree you are looking at.

NOTE: These two mods were intended for use with the American side of play. So, let me know if your scope mods are only for the German side. If they are, I'll make you a German mission and put the Big Compass Bearing on the German periscope.

Once you have the mods running on a stock game, go to the periscope and choose the low power magnification. Try to put the center line of the scope directly on a degree mark (does not matter what it is) and make sure one of the outer edges of the scope is lined up on a reference point of a ship background (again, it does not matter what reference point you choose, or whether you go left or right) but choose a reference point that you will find easily and precisely when you do the next step. Move the scopes center line onto the point you picked out at the edge of the scope. Now read the compass bearing (and be exact; no almost, or just a bit off will do). The difference between compass degrees of where you started and what the reference point compass bearing reading is will be half the true field of view for the scope. If you count 18 degrees difference between the center line bearing and the edge bearing you measured to, the True Field of View is 36 degrees wide. To see some images of doing this, check out the first couple of posts in this thread.

I could do math all day and couldn't get the "AngularAngle=62.4814" to end up being a true FoV of 36 degrees when the game is running!! BUT, That's what it is!!

So, find out what your specific French periscopes Field of View and Magnification in real life really is. Make a "Periscope_Mask" image to suit the French style (if the French uses the 32 degree FoV, simply measure the Alpha channel black image and divide the width of pixels by 32. This will give you the correct spacing of the Telemeter divisions to put onto the periscope_mask. Every image is different, for instance my periscope images I'm using for Optical Targeting Correction are larger than the stock periscope viewable size. The viewable image size is 768 pixels wide (least wise that's the size on a 1024x1024 canvas). Dividing 32 into 768 you get 24 pixels. So, there is 24 pixels between each Telemeter division on my scopes. This will give you the correct measurement for the FoV of the scope you make, you just need to re size the AngularAngle and Magnification of the Camera.dat file to have the view match the 32 degree width of the scope you made.

You may ask, How did you make the AngularAngle come out to the correct FoV size?

The old saying "If you don't succeed the first time try again" was the way I got it. You know Thomas Edison did hundreds of tries to find the right metal element to put into his light bulb before he found tungsten worked the best. Well, after changing the magnification parameter to what the American scope should be, I just kept fiddling with the AngularAngle until I came up with the correct FoV when I'd restart the game using my "Test 21" mission. No math, I'm just too stupid to know what to do (in this case)!!

[CapnScurvy]

Originally Posted by keltos01

so it's 6° FOV at 6x zoom and 40° FOV at 1.1x zoom for the french attack periscope

While I was writing my previous post, you found the French periscopes specs. Good

Leave it to the French to come up with such an odd combination.
High Power is 6x magnification with a 6 degree FoV
Low Power is 1.1x magnification with a 40 degree FoV

The point is they don't add up with each other like the American periscope.
High Power is 6x magnification with an 8 degree FoV
Low Power is 1.5 magnification with a 32 degree FoV

You see, the American figures are of a multiple of 4 which help in keeping a target height or length in a direct connection, whether you use either the high or low power magnification. For the French to use the Telemeter division marks, there was probably a set just for the low power magnification and a separate set for high power.

And, since the French have such a different Low Power FoV of 40 degrees (the German periscopes were 32 degrees), my Omnimeter for finding range when counting the Telemeter divisions up to a known height will be useless.


=========

Keltos, I noticed something else about the "AngularAngle=" on the Silent 3ditor image you posted. That figure should read 62.4814 not 62,4814. Put a decimal point after 62.