Interesting Findings on the Airstrike

[absolute_imperial]

So I was playing through Black Mesa again and I got to my favorite part of the game: the airstrike on the desert facility while you are on the cliff. I’ve always thought the visuals of this part as well as the massive scale of the scenery were very enlightening.

I began to wonder what the actual scale of the entire scene was. To determine it, I timed the shock wave from its instance to when it reaches the player on the cliff. The average time is almost exactly 3.5 seconds. Knowing the shock wave travels at the speed of sound in Earth’s atmosphere, I calculated the distance from the player to the facility. It is about 1.232 km or roughly 0.77 miles.

I was somewhat disappointed in my findings because it appears at least visually that the facility is about 2 to 3 miles away. If that is the appearance the Black Mesa team was going for, the jets and the shock wave should have both traveled considerably slower.

I’m sure I’m not the first person to think to check this, but I thought it was worth sharing none the less.

[Dotard]

Wow, some fans simply can’t help but to analyze everything under microscope.

[Swaggless]

It’s actually pretty cool that you found this out… I don’t think it matters too much, though. If it took much longer, it’d take TOO long.

Besides, those are super-secret, experimental, super bombs developed by BM that have a supersonic shockwave. Problem solved!

[bur]

@absolute_imperial

I’m sure I’m not the first person to think to check this

I think you might be

[Ronster]

BOOM!!!

[absolute_imperial]

@Swaggless

It’s actually pretty cool that you found this out… I don’t think it matters too much, though. If it took much longer, it’d take TOO long.

Besides, those are super-secret, experimental, super bombs developed by BM that have a supersonic shockwave. Problem solved!

Oh I agree it doesn’t matter too much, a slower shock wave may have been a bit boring by comparison, but I thought it was an interesting finding…

[absolute_imperial]

@stormseeker

I did all the calculations before hand, and tested them. I can give you the numbers if you want them.

18 seconds was far too long for the scene, and interfered with the jumping puzzle, so it was deliberately reduced to 11 seconds as per testing.

We have to reduce realism sometimes to improve gameplay.

Oh awesome, it’s great that you took the time make the calculations. Those numbers would be interesting to see. It would make sense that a longer time lapse would lead gameplay complications.

[RK1]

Decompiling maps also helps in determining exact distances.

Given:
Distance between cliff and base is approx 5708 hammer units.
One hammer unit in skybox = 1 foot.

That gives us 5708 feet, or just a little over a mile.

That actually is much closer to your calculations, I think.

Source: https://developer.valvesoftware.com/wiki/Dimensions

EDIT: On further considerations if you use the measurements they use for humans (which is 12 units per foot (which is 16/12 feet per skybox unit), the measurement between the cliff and the base becomes more like 7135 feet, which is Which is about 1.35 miles.

[Swaggless]

@stormseeker

First of all it’s important to note that Level Designers tend to use the human comparison (because Gordon is not 4ft tall) for scaling in Hammers unit system, whilst we use the standard of 128 units for wall height etc, we rarely use that for actual corridor heights as it looks odd. As such we use the 1unit = 1" rule rather than the .75" actual. It’s why you’ll often find info_player entities scattered around the map.

As such my calculations were as thus.

Date of incident 16th May (average temperature outside is usually between 50F and 80F in new Mexico, however the high on that day was 105F - [105-32/1.8 = 40.5c]

Spd of sound @ 20c = 343m/s approx (767.3 mph)
Spd of sound @ 40.5c = 355m/s approx (794.1 mph)

Distance to Comms Base Facility from skybox camera is at an angle, therefore:

O - 2783 units
A - 5477 units

H = 2783^2+5477^2 = ¬37742618 = 6143.5 units (6144 units)

angle = 2783/5477 = 0.51 tan^-1 = 27 degrees.

6144 units @ skybox scale (0.0625 or 1/16th) = 98304" or 8192’ (8192/3.2808 = 2496.9 [2497m]) or about 2.5km (1.55 miles)

Therefore the Shockwave from the blast should be 2497 / 355 = 7.03 seconds.

Actual shockwave timing as per entity reduction (for gameplay purposes)

= 3.6 seconds. [This is based on the trigger onPass from the planes, enacting .55 seconds after the planes pass the pathtrack point ‘b_pt09a’ to allow for bomb drop timing, up until the sound is played at 4.10s in from trigger - ie 3.55s]

This would mean the actual speed of the shockwave is approx 695m/s or 1554.7 mph. Which would require an air temperature of 1000c, so obviously not accurate.

---

Speed of the planes.

“on trigger set speed 750.”

AV8-B.II for USMC max speed = 673 mph
750 units = 1000ft/s or 304.8 m/s = 681mph

however there are the AV8-A and AV8-C variants that have a top speed of 731mph, so this is not unreasonable.

Distance therefore takes - 8.2 seconds to reach the base.

Total time for full scene (approx) -

Original before testing = 15.23 seconds.
After testing and reductions = 11.8 seconds.

so about 3.4 seconds sooner than in reality.

That was really interesting. A lot of work and thought went into that. Thanks!

[Dotard]

Wow, I wish I had that kind of brain.

[CPU]

@Dotard

Wow, I wish I had that kind of brain.

Yeah, but you don’t. After all, you are an admitted dotard.

[Narfin]

I’m always amazed at how much thought and attention to detail went into this game. I love developer posts like this and the questionable ethics one, they make me appreciate why the mod took as long as it did.

[Cat_Fuzz]

NM

[absolute_imperial]

@stormseeker

First of all it’s important to note that Level Designers tend to use the human comparison (because Gordon is not 4ft tall) for scaling in Hammers unit system, whilst we use the standard of 128 units for wall height etc, we rarely use that for actual corridor heights as it looks odd. As such we use the 1unit = 1" rule rather than the .75" actual. It’s why you’ll often find info_player entities scattered around the map.

As such my calculations were as thus.

Date of incident 16th May (average temperature outside is usually between 50F and 80F in new Mexico, however the high on that day was 105F - [105-32/1.8 = 40.5c]

Spd of sound @ 20c = 343m/s approx (767.3 mph)
Spd of sound @ 40.5c = 355m/s approx (794.1 mph)

Distance to Comms Base Facility from skybox camera is at an angle, therefore:

O - 2783 units
A - 5477 units

H = 2783^2+5477^2 = ¬37742618 = 6143.5 units (6144 units)

angle = 2783/5477 = 0.51 tan^-1 = 27 degrees.

6144 units @ skybox scale (0.0625 or 1/16th) = 98304" or 8192’ (8192/3.2808 = 2496.9 [2497m]) or about 2.5km (1.55 miles)

Therefore the Shockwave from the blast should be 2497 / 355 = 7.03 seconds.

Actual shockwave timing as per entity reduction (for gameplay purposes)

= 3.6 seconds. [This is based on the trigger onPass from the planes, enacting .55 seconds after the planes pass the pathtrack point ‘b_pt09a’ to allow for bomb drop timing, up until the sound is played at 4.10s in from trigger - ie 3.55s]

This would mean the actual speed of the shockwave is approx 695m/s or 1554.7 mph. Which would require an air temperature of 1000c, so obviously not accurate.

---

Speed of the planes.

“on trigger set speed 750.”

AV8-B.II for USMC max speed = 673 mph
750 units = 1000ft/s or 304.8 m/s = 681mph

however there are the AV8-A and AV8-C variants that have a top speed of 731mph, so this is not unreasonable.

Distance therefore takes - 8.2 seconds to reach the base.

Total time for full scene (approx) -

Original before testing = 15.23 seconds.
After testing and reductions = 11.8 seconds.

so about 3.4 seconds sooner than in reality.

Wow, I must say I am quite impressed with the attention to detail you put into calculating the shockwave, even paying attention to the temperature dependent variance and net displacement of the player to the base. Well done

[Dadster]

@Stormseeker, I ran your numbers through my trusty slide rule, and they are bang on.

[Vinylshadow]

kinda makes you wonder how fast Gordon runs, given how many Hammer Units are in an in-game mile…

[k3nny1550]

Gordon’s sprint speed is 13.6mph.
Don’t know if Black Mesa changed this speed.