[neistridlar]

As is my custom, I have spent way too much time over the last few days thinking about how one could make a spotting system for wolfpack that would feel realistic, and reward playing as is described in the literature from WWII. It is based on my own experience as a lookout on recreational vessels at sea, together with reading a translation of the U-boat Commanders handbook. Also some Ideas are lent from other games, like KSP and Cold waters.

So, here is what I envision: Each ship will have a number of lookout points. These lookout points have a sector in which they can look. They also have a scan period/frequency, a detection threshold, and a spotting score. The scan period is in part for performance reasons, and in part to emulate how a lookout may sweep back and forth along its sector. Detection threshold and spotting score will make more sense later.

1. On the U-boat there will be 3 checkpoints, one at the top of the bow, one on the top of the stern, and one at the highest point of the boat with all equipment extended (probably on top of the attack periscope).
   1. First a simple check is made, whether any of these points are above a min depth plane. This plane would reflect the visibility of the water itself. In my experience this would typically be around 5m, but may vary between 1m and 20m. If no points are above the plane, visibility score is 0, and no further checks are needed.
   2. Next the distance to the points are checked. If they are not within the visible range, same as before, no further checks are needed, visibility score is 0.
   3. Next we check for obstructions. All ships are replaced with a very simple model, like a box, for performance reasons. A ray trace is done to check for obstructions. Again, if no points pass this check, visibility score is 0, and no further checks are needed.
2. This is where the real “meat” of this method is. In order to find a score we do a simple render. To keep the performance impact down the quality of this render should be kept as low as possible, think 1990s levels of graphics. Also, a low resolution and a narrow field of view should be used (similar to the field of view in the binoculars).
   1. The u-boat is rendered diffuse light gray. Except for the glass on the periscopes, which are specular, in order to make them glint in the sun.
   2. The sea is rendered as black fog. The thickness of the fogg is according to visibility, like with the depth plane.
   3. The surface of the ocean is rendered so that it is transparent when viewed head on, and black at oblique angles. That way you can “hide” behind waves, but the boat may still be visible, even submerged at close range, and fully submerged in clear water. Also this mimics the way water reflects the sky at oblique angles more than right angles.
   4. Ships render black.
   5. Black fogg, according to visibility conditions.
   6. Black “glare” post processing according to sun-direction.
   7. Other effects, like spray from the periscope or wakes at high speed could also be rendered light gray.
3. Visibility score is calculated simply by summing up the values of the pixels in the render (black being 0, and white being 255). So if more of the boat is visible, either because it is closer, or for instance surfaced, and showing its broad side, the higher the visibility score is. While attacking out of the sun, while low on the sky, will blind the enemy, and render the boat almost invisible.
4. Here is where my own experience, U-boat Commanders Handbook, and Cold Waters come into the picture. Every lookout has a spotting score (from 0-100), that works similar to the “solution” in Cold Waters.
   1. Visibility score is compared with the detection threshold.
   2. If the visibility score is below half the spotting threshold, spotting score is reduced by 50 points.
   3. From visibility score between half the spotting threshold and the spotting threshold, the spotting score is reduced between 0 and 50 points, proportional to how much lower it is.
   4. Similarly, above the spotting threshold, up to 200% of the spotting threshold, spotting score is increased between 0 and 100 points, proportionally to how much larger the visibility score is. So at close range, you can be detected immediately, but at longer ranges detection takes longer.
5. Spotting scores above 0 may trigger warships to get suspicions, and act accordingly. The chance would increase as the spotting score increases.
6. At 100 points, you are definitively spotted. Great speed ahead

The reasoning behind the visibility score, is from my own experience spotting things at sea. Your eyes will frequently play tricks on you, leaving you to think you might have seen something, but often you can not find it again. Other times they will appear again, when you have closed distance, or it appears from behind a wave. This is especially true for fishing equipment, which like a periscope is just a small speck dipping in the waves. Also, as is written several times in the U-boat Commanders Handbook, at close range the periscope should be used sparingly, but frequently, and be kept as low as possible, with the ocean washing over it constantly. Using the periscope this way would then make the spotting score raise more slowly, or even be completely arrested by alternating between increasing and decreasing.

Oh boy does it feel good to get all that out. Now I invite you to tear it apart, and figure out why it would be good/bad, or how it could be better.