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69thSpiritus_Mortem

TFS Update 07/22/2017: The Last Steps

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While the northern hemisphere is sizzling away from summer heat, work on TFS 4.5 is getting closer and closer to completion.  We want to thank everyone (yes, even you critics and naysayers) for being patient, especially within the last nine months. We know a lot of you out there are wondering about all the aspects you read about when news broke of the deal between TFS and 1c, I ask you again for your patience. Everything you read before is still planned and in the works, but the biggest priority for us is the completion and delivery of TFS 4.5 before anything else. 

 

Being the mind readers we are:

 

We will not divulge a release date. This is TFS's policy and won't change for numerous reasons. With that said, we hope you'll be able to see the light at the end of the tunnel after reading and watching the update below, because we can. 

 

And now for the reason why you all have bothered reading to this point. Grab a drink or three of your choice, your reading glasses,  and get comfortable, there is a TON to chew on here. Starting with a surprise that everyone has been waiting for. 

 


 

While working to update the Speedtree 5.2 program to DX11, our resident genius and chief Coder Colander found a way to implement tree collisions... without inflicting a huge FPS hit. In most games the player's aircraft location is constantly compared to the location of all the trees in the game on a split second basis... a huge load on the computer considering there are millions of trees.

 

Colander wrote code that simplifies this:

 

a) divides the total number of trees in the game into "forest blocks".

b) compares the player's aircraft to each block... a much smaller number to crunch

c) only if the player plane's location is close to a "block" are the trees within the block in question then compared to the players aircraft location... and detailed calculations are only done for those trees which are within a certain distance. 

 

:)

 

Now on to the meat of this update... Flight Modeling. Get comfy. 

 

Those who are easily bored may want to tune out here... this update is for the Gear-heads... yes you will need to think about what you are reading and the videos are more focused on the detail rather than the eye candy.

 

IL2 STURMOVIK Cliffs of Dover is a simulation and Team Fusion understands that. From the beginning one of the core essentials of our work has been to provide as accurate a modeling of the various CoD aircraft as possible. TFS 4.5 is the culmination of a lot of Flight Modeling work... either to fix existing bugs in the game, or to add new features which will add further dimension to the player's experience.

 

One of the biggest issues with the original game, one which was only partially solved with TFS 4.312, was the so called 'Altitude Density Bug'... probably better titled, "Power modeling with increase in altitude ".

 

Before I detail the fixes... a simplified explanation of CoD's physics system:

 

The game has a base physics engine... which calculates air density, gravity, weight, wind speed, friction, etc, etc... this interacts with  three discrete aircraft systems.

 

a) Engine power.

b) Prop thrust as generated by the engine/s powering the rotation of blades, (with the blades having their own aerofoil characteristics, and at a specific rpm determined by the engine/prop governor).

c) Aircraft aerodynamics... incorporating in the latter for example, aerofoil lift/drag as well as the drag generated by the aircraft in its 'clean' configuration...  and this modified by the additional drag generated in various 'dirty' configs... i.e. gear down/up, flaps, down/up, canopy open/closed, rads open/closed, etc. 

 

How engine power is handled is a complex element in CoD... the game has as detailed a model for this as any game out there. Start with the basic elements... engine displacement, number of cylinders, compression ratio, carburetor type, (fuel injection or specific carb type, as modified by the size of venturis, means to introduce fuel into the charge, etc. ) throttle systems,  (linear, density based, manual) add in mix systems, (fuel injectors, auto rich/lean, manual metering) and on top of that, the supercharger characteristics... the critical element in WWII aircraft performance... with a supercharger's capability to generate a certain number of atmospheres of pressure up to a certain altitude being the key... some superchargers being single stage single speed types, (ie. with a single impeller running at one rpm) and others being multi-speed, (with the option for two rpms to be selected, low or high), or the more efficient fluid drive multi-speed, like the Daimler-Benz types in the 109's... with a hydrocoupling system which allows the rpms to increase with altitude.

 

There are also multi-stage types... with two superchargers in sequence, one piggy-backed on the other, the second kicking in at high altitudes... in this case, first one supercharger compresses the atmosphere, then the second takes the already compressed charge, and compresses it further... or a Turbo-supercharged system as seen in the Pratt and Whitney R2800 in the P-47... whereby a multi-rpm turbocharger first compresses the atmosphere, then forces that charge into a single speed supercharger at the engine, which then compresses it further... etc. etc. The important factor in all being as the atmospheric density naturally decreases with altitude, the quantity of density of the fuel/air charge which can be forced into the combustion chamber without the assistance of a supercharger decreases as well... and without charge density, power is reduced.

 

All of this is replicated in the game's code with a whole series of interacting equations... modified by the individual aircraft characteristics... it is a really elegant system... Oleg's idea for how power was generated and modified was brilliant, but the problem was that the game's original math was flawed.  

 

The power generated by the engines in effect was off by approx. 15% at sea level... and to add complexity to the error...  as altitude was gained, the power would fall off at an increasing rate... greater than 15%... power loss to the bug was an ascending curve.

 

Now, some of you might say... "What's the big deal... add more power and the planes will climb higher."

 

And yes, it is simple enough to add more power to allow the aircraft to reach their historical ceilings... but then they are much too fast at sea level and climb times resemble jets more than prop types. We were and are thinking of the future... The historical fact was combat in WWII took place at increasingly high altitudes as the war continued. Aircraft engines had higher and higher full throttle heights. In order to make CoD accurate, and to ensure any new expansions would have aircraft performance accurate at high altitude, we had to fix the bug. If we want to model the contrail busting combat of 1943/44 with the 8th Airforce and the P-47's, P-51's and 190's, we need to get the power equations right.

 

But getting the power curves to match through the altitude range is a complex process.

 

Here's one example of historical engine curves and our modeling... I will use the Daimler-Benz DB601A, because it is the most complex of all the types to model in CoD. It uses a Single Stage Supercharger, but with the speed, i.e. the rpm which the supercharger impeller turns is controlled by a "Hydrocoupling" clutch... which allows the Supercharger to spin at a gradually faster speed as the altitude increases. This in effect gives the advantages of a Single Stage Two Speed Supercharger... but with a much smoother transition between the speed changes and less potential power loss.

 

Below is an original source diagram from the DB601A/B manual illustrating the PS (metric Horsepower) produced through the altitude range. The key line is 1.30ata boost and 2400 rpm.  That traces the level of compression the DB601A (with 'Neuem Supercharger') can generate up to its 'rated' altitude... ie. the standard DB601A can maintain 1.30ata boost up until 4500 meters height at which point it is producing 1020 PS (Metric HP).

 

post-18684-0-04801900-1500732326_thumb.png

 

As mentioned, the original game's power calculations were way off. In TFS 4.312, without the Source Code, and under pressure to get a decent release out before everyone left, we had to compromise. The result was a DB601A with slightly too much power at low altitudes, but with the power falling off at high altitudes despite the temporary fixes we added. If you look at the chart below, original vanilla CoD power at 1.30 ata/2400 rpm would be the orange line, completely inaccurate... and the reason the aircraft were so slow in the original game and why they didn't climb.  At the same settings power for TFS 4.312 would be the red line.  Both lines do not model the characteristic curves of a Hydro-coupling supercharger. In TFS 4.312 we had to trade off between not making the 109's too fast at sea level and full throttle height and not crippling their climb at high alt.

 

Neither was entirely successful.

 

post-18684-0-79194500-1500732632_thumb.png

 

Moving on to today... and after nearly a two year struggle, most of which was without SC access we have our new power formula.  Below is a chart from our TFS utility to model power... and using our new math. Compare it to the original chart at 1.30 ata and 2400 rpm and you will see an almost perfect match... only at sea level is it out a bit... 20 PS too high.... but we can tweak the sea level performance using some other parameters.

 

post-18684-0-66749200-1500732661_thumb.png

 

Almost all the credit for this work has to go to Colander, our chief coder.  He had to teach himself the details of supercharged engine theory, then find the error in the original CoD code, (without access to the SC) and then write new equations, and translate them to code form.  In all it was a nearly two year process, with some 20 plus Alphas to get it right.  My own contribution was limited to providing the original source data for the various engine types, harassing Colander to re-do his math if it wasn't perfect, and having the fun of creating the new FM's afterwards.  

 

One of the big advantages of having a known value for engine power, is we can now model the aerodynamics more perfectly. Previously when modeling turn rate, not knowing exactly whether the power characteristics were correct, we had to largely estimate the aerodynamics to match game performance with the historical turn rates... now we can be much more precise in the area of modeling max cl/max drag, induced drag, etc. etc.

 

As part of Colander's engine changes, he also was able to revise the prop thrust equations. So now we have much accurate modeling in that area; takeoff runs with the new math are shorter, aircraft accelerate faster thus take less distance to get airborne. Whereas in the vanilla game and in most of TFS 4.312 props were generally left alone due to the uncertainties of the power equations (they mostly used generic values), in TFS 4.5, we will see props which more accurately model the characteristics of the real thing. In prop design there is a trade off, some props are designed to give low drag at low angles of attack, but lower thrust at high AoA... the result is less performance in a climb, but higher level speed. Others have higher drag at low angle, but high thrust at high AoA... better climb, etc.

 

One other detail.... Fuel injected engines now require a warm-up in cold weather as well as carb equipped types... so the 109's will need to sit for a few moments while their water/oil temps come up.

 

The next video is a demonstration of the more accurate climb ceilings for aircraft which will be seen in TF 4.5... it is of a 109E-4N climbing to ceiling (edited for brevity).

 

In the vanilla game 109's couldn't get past 7000 meters... in TFS 4.312, they were lucky to reach 10000 meters and had to watch the Spits and Hurricanes climb past.  That was a result of the fact that the lower wing-loading of the British aircraft gave them an advantage which was not countered by the historically better power-loading of the German types at high alts.

 

Also note the pilot has to check the engine temperatures when nearly at ceiling to make sure he doesn't overheat his engine... in TFS 4.312 we modified the overheat system to reduce heat generation at high altitudes in our effort to increase aircraft ceilings... but now that mod is gone and the extremely thin atmosphere at 30,000 ft/10000 meters plus altitudes does not reward pilots who run their engines at max rpms... and all climbs at that altitude need to be done at full radiator openings.

 


 

Another aspect of the new engine model is overheating. 

 

While building TFS 4.312... with an average of 15% more horsepower required to be added and the game's physics engine calculating overheat in a logical way meant we had to introduce a mod to reduce heat generated. Unfortunately as part of that, the subtleties of engine damage due to overheat which were in the original game were lost.  :(

 

What this meant in concrete terms was in TFS 4.312 an overheating engine gave only a single result... blown radiators at the point the pilot exceeded exactly the maximum recommended water temperature. Which of course, is not accurate.

 

With HP now historically accurate, and heat generation based on those numbers, we can drop our mods and re-introduce the range of damage which might be encountered by a pilot who unwisely abuses his engine. In addition to water temperatures, pilots also need to be more careful of their oil temps... in CLIFFS OF DOVER exceeding or approaching the maximum recommended oil temperature reduces the viscosity and lubricating properties of the oil and therefore increases friction... which means a drop in horsepower generated and poorer performance.

 

Damage can now range from the relatively minor result of a blown head gasket, to an oil leak, to a prop governor failure, or to a whole gamut of damage including a burst radiator and fractured water jacket. So sometimes a pilot might be able to fly home without much difficultly, other times he/she might find himself taking a swim in 30 seconds. There is an element of randomness in the damage as well, exceeding the maximum allowable temperatures are not necessarily a guarantee the engine will fail but a pilot who takes that chance might be out of luck.  

 

To paraphrase.... "Do you feel lucky flyboy?"

 

Below is a video which illustrates the various results of engines being abused. The first example has a 109 taking off with 25% Rad and Oil opening... the next has a Spitfire sustaining +12 boost at low speeds at 50% rad opening, and the final clip shows a 109 taking minor overheat damage and flying back to its field and landing. You will also see the shorter takeoff run in the 109.

 


 

The Flight Modeling Team has also focused on the details and the overall accuracy of the aircraft.

 

For example, ensuring the correct carburetor/fuel injection types for each aircraft, ensuring the mix systems are correct, and ensuring the prop pitch governor types are accurate.  As one example, the Blenheim will have an auto rich/auto lean mix system, (like the Spits and Hurris) instead of the incorrect system currently in place which requires adjustment through the altitude range. I could go on, but nearly all the aircraft types have had improvements in one area or another.

 

We are also introducing prop feathering for aircraft which historically had this capability (mostly German at this stage in the war).

Below is a video of a Bf110C-4B which has the pilot feathering the prop on the left engine after taking overheat damage on it. The C-4B is one of the new 110 types being introduced (more on the C-6 in the next update). The C-4B had the DB601Ba low alt engine, rated at 1.45ata/2500 rpm max. power output and should be the fastest 110 at sea level.

 

The 110's are an example of an aircraft type which benefited from the new engine math. In TFS 4.312 we had to give the 110's nearly 20% more power to allow them to approach a climb and ceiling near historical but this meant they were much too fast at sea level so we had to add drag to slow them down.  This made them overly sluggish and prone to lose energy in turns. With more accurate engine math and horsepower modeling through the altitude range, we are able to drop the excessive drag and the 110's are now more nimble and maneuverable... especially the C-4B on the deck with its low alt engines.

 


 

 

 

How about a quick, small recap of a few bullet points about 4.5 before moving on?

 

:wacko:

 

- 3D work and texture work is basically finished. Small details may need tweaking. 3D department shifted focus on  5.0 work weeks ago. 

- All mods have been officially written to the SC. New additions (like prop feathering) may need further adjustments to the code.

- Collidable trees, did you notice? Your frame rates barley did. 

- Codework underway to animate and import 3d models. 

- Testing has now started within TFS

- CloD now uses DX11

 

And if that isn't enough, here is a little more for you all, particularly about the channel map and those pesky bugs.

 

The distant river fix has really changed the look of the map, with the new textures flowing seamlessly now.

 

post-18684-0-08536800-1500733275_thumb.jpg

 

And speaking of the new textures, the French land textures can join the new textures for England, which brings a fresh, authentic, and awesome new look to the channel map. 

 

post-18684-0-75276700-1500733296_thumb.jpg

 

And finally, our map team has also been burning the candle at both ends and making great progress on the channel map and the new North Africa map. The images below do not show map files or screenshots from the map editor, but instead are visual tests for them to see if the "map-files-reading-decoding-manipulating-encoding-writing back" code they are writing is working properly, by letting them "see" the data. 

 

post-18684-0-62813600-1500733351_thumb.jpg

 

post-18684-0-78872800-1500733367_thumb.jpg

 

post-18684-0-69238300-1500733388_thumb.jpg

 

post-18684-0-07822100-1500733408_thumb.jpg

 

Among many things, this should also open the door for properly correcting those pesky errors, like sea depth issues, incorrect textures, height issues, odd bodies of water, landmines at airfields, so on. For instance, bug 599.

 

post-18684-0-17981700-1500733438_thumb.jpg

 

post-18684-0-87884500-1500733468_thumb.jpg

 

And I almost forgot, here is a video of a working mirror in a Hurricane... we are very happy to introduce this element... again due to Colander finding the bugs in the code and writing new software to implement it. Smooth frames, again with little FPS hits. 

 


 

As always, please keep reporting bugs or issues you have on our bug-tracker located at the link below. We do frequent it and take note of your posts/requests so thank you all for registering and helping out. 

 


 

I'm sure your beverage is now empty so we will leave it at that. Hopefully there was something in this update to make everyone smile or get excited about. We know you all want this release, and we want to release it more than anyone can imagine. Things are looking great and progressing well for both announced patches, and once TFS 4.5 is released some of those other aspects and questions you may have can start to get answered and showcased. 

 

Until then though, happy flying. 
Edited by 69thSpiritus_Mortem
  • Upvote 24

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Great update, lot's of technical progress has been done. Congratulations!

 

I'd suggest one improvement to the updates: have the YouTube videos have a proper title and description. You really want people who wonder off to these gems to understand what is being showed instead of only having a generic title and absolutely no description.

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Absolutely excellent. I can't wait for this, and I am sure with TF 5.0, we will be seeing a whole new level of sophistication, as well as expansion to the best and most underrepresented theater of the western air war.

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Whoo hooo can't wait to get in there again especially with the new mirrors and engines and trees this is good news!!! and yes great!

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If we want to model the contrail busting combat of 1943/44 with the 8th Airforce and the P-47's, P-51's and 190's, we need to get the power equations right.

This things sound great, .. You have my support if you finally decide to do it. 

 

"Hydrocoupling" clutch... which allows the Supercharger to spin at a gradually faster speed as the altitude increases. This in effect gives the advantages of a Single Stage Two Speed Supercharger... but with a much smoother transition between the speed changes and less potential power loss.

Relative to this issue, don´t forget that a real tactic of the lufwaffe pilots were pulling the enemy fighter in to a vertical combat, in the engine supercharger inter-stage altitude, (about 12,000 ft or 3,500 mt.) for over-performing them.

I think that the lacht of power that Merlin engine suffered at that altitude, must be accuratelly modelled, and you don´t mencioned this thing here.

I hope that you had thinking to modelled this feature too. 

 

 

One other detail.... Fuel injected engines now require a warm-up in cold weather as well as carb equipped types... so the 109's will need to sit for a few moments while their water/oil temps come up.

Yes, all engines need a warming time, for give the maximum power, ..but in the case of the DB-601 equipped with DIRECT FUEL INJECTION, in to the combustion chamber, it is very diferent to injecction carburator in to the supercharger inlet.

The warming time for the DB-601 is almost few minutes), because there not fuel condensation in the inlet manifold like in the RR Merlin engine occurs.

By the way, The luftwaffe used heater trolleys for cold weather operation.

 

19884252_10214007604886479_6445869300587

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Great update, lot's of technical progress has been done. Congratulations!

 

I'd suggest one improvement to the updates: have the YouTube videos have a proper title and description. You really want people who wonder off to these gems to understand what is being showed instead of only having a generic title and absolutely no description.

 

Thanks for the constructive feedback. Went back and added a little. This update was a little different than usual with all the videos, but for our normal single video updates I will have a better description for sure!

Edited by 69thSpiritus_Mortem

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This things sound great, .. You have my support if you finally decide to do it. 

 

Relative to this issue, don´t forget that a real tactic of the lufwaffe pilots were pulling the enemy fighter in to a vertical combat, in the engine supercharger inter-stage altitude, (about 12,000 ft or 3,500 mt.) for over-performing them.

I think that the lacht of power that Merlin engine suffered at that altitude, must be accuratelly modelled, and you don´t mencioned this thing here.

I hope that you had thinking to modelled this feature too. 

 

 

Yes, all engines need a warming time, for give the maximum power, ..but in the case of the DB-601 equipped with DIRECT FUEL INJECTION, in to the combustion chamber, it is very diferent to injecction carburator in to the supercharger inlet.

The warming time for the DB-601 is almost few minutes), because there not fuel condensation in the inlet manifold like in the RR Merlin engine occurs.

By the way, The luftwaffe used heater trolleys for cold weather operation.

 

19884252_10214007604886479_6445869300587

All engines have been remodeled... the new engine code and accurate horsepower at altitude applies to all types.

Edited by Buzzsaw
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We will not divulge a release date.

 

 

You've got to be kidding?  :o:

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Nope.  :)

 

You can probably make an educated guess though. 

 

Yes, I probably can but.....

 

Without a release date there's nothing that exciting or - trees excepted - new in this update.   

 

Now is the time to be bold, take the initiative and give the community some sort of a firm date on delivery.   I'm quite sure there are many good reasons not to do this from TFS's point of view but time, promises and other games march on relentlessly and the community moves with them.....................

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Relative to this issue, don´t forget that a real tactic of the lufwaffe pilots were pulling the enemy fighter in to a vertical combat, in the engine supercharger inter-stage altitude, (about 12,000 ft or 3,500 mt.) for over-performing them.

I think that the lacht of power that Merlin engine suffered at that altitude, must be accuratelly modelled, and you don´t mencioned this thing here.

I hope that you had thinking to modelled this feature too. 

 

The Merlin III and XII currently modelled are single-speed, single-stage engines, there therefore is no "inter-stage" or supercharger gap. Even the Merlin 40/50 series found on the Spitfire Mk.V only had a single-speed, single-stage supercharger. Only the Merlin XX of the Hurricane Mk.II that's coming in 5.0 is going to have a two-speed supercharger.

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The Merlin III and XII currently modelled are single-speed, single-stage engines, there therefore is no "inter-stage" or supercharger gap. Even the Merlin 40/50 series found on the Spitfire Mk.V only had a single-speed, single-stage supercharger. Only the Merlin XX of the Hurricane Mk.II that's coming in 5.0 is going to have a two-speed supercharger.

Yes you are right. But in any case, The Merlin III automatic boost control was worst in efficiency, because blow out the mixture air-fuel when the manifold reached rated pressure.
And in any case, the single -speed, single-stage Merlin engines performance over 12,000 ft ( about 3,500 mt) was worst than the DB-601 with same fuel 100 oc.. 

Thanks you for the corrections  ;)

Edited by III/JG52_Otto_-I-

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By the way, The luftwaffe used heater trolleys for cold weather operation.

Those Bf-109s are Romanian.

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Brilliant update. Thank you for giving us all that information to review and examples in video. I couldn't help but giggle watching the wing come off in that first video. S!

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Great work and continue!
I think it might / will be my favored flight simulation!

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For those who noticed I didn't completely stop the prop on the Bf110 when feathering it... here is a video of feathering the prop on a Ju-88A-1 and landing on one engine.

Note: Sometimes it is better not to stop an engine if it is not too badly damaged... because the engine might power an auxiliary element in the aircraft... for example, the hydraulics, the compressed air, etc. When the engine is not running, there is no power to run those auxiliaries.

Please note also, I should have locked my tailwheel prior to touching down... as you will see later.

 

My first time landing a Ju-88 on one engine so easy to forget.  :)

https://youtu.be/6XVgsyPbdac

Edited by Buzzsaw

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What a fantastic update, I love the little details  :biggrin:  It's great to see how fixing one area (HP) has positive knock on effects in other areas of the sim.

The tree collision was completely unexpected and so welcome.  Finding a suitable crash landing site will become so much more important now.

 

Colander really sounds like he's getting to grips with the source code.  The sky really is the limit now.

 

Thanks for all your efforts guys, it really is appreciated.

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