GPL 1967 v3 Dev blog

Discussion and releases for the 1998 racing simulation by Sierra/Papyrus
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#121

Post by PTRACER »

Bottom post of the previous page:

Michkov wrote: 6 months ago The Ferraris had their rear disks inboard, cooled by an airscoop at times iirc. I'd need to look up the other cars to be certain, but inboard brakes at the rear weren't that uncommon for the period.
Image

And if you want to take the idea even further, why not mount the sole rear brake directly to the gearbox output shaft like the on BRM P48.
Image
I had a feeling that BRM brake wasn't effective and I was kinda right...Two brake failures in 1960, one of them resulted in the death of a spectator (Gurney at Zandvoort).

At any rate all this presents a good case for rear brakes having poorer cooling than the fronts!
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#122

Post by Michkov »

Comparing the 49 to the other 6 cars, the Lotus should have the best cooling. All four brake disks are in the airstream with little to obscure airflow to them. All other chassis have their front brakes tucked into the rims, with all but the Ferrari running outboard rears. So from a first approximation on cooling efficiency, the Lotus should be the best, with everyone else below it. There are also quite a range of brake duct variations across the season. Although, I'm not sure if the exposed brakes on the 49 are to improve cooling or allow larger disks to be used. Its predecessors all have the conventional disk inside the rim arrangement.
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#123

Post by PTRACER »

Michkov wrote: 6 months ago Comparing the 49 to the other 6 cars, the Lotus should have the best cooling. All four brake disks are in the airstream with little to obscure airflow to them. All other chassis have their front brakes tucked into the rims, with all but the Ferrari running outboard rears. So from a first approximation on cooling efficiency, the Lotus should be the best, with everyone else below it. There are also quite a range of brake duct variations across the season. Although, I'm not sure if the exposed brakes on the 49 are to improve cooling or allow larger disks to be used. Its predecessors all have the conventional disk inside the rim arrangement.
The other *six*? :mrgreen: If you think that it adds value I can add additional code for specific cars, i.e. Lotus gets "100%", Ferrari "60%" and all other cars "80%". (Or I could try to do individual cooling rates for each car but then it starts to become harder to manage all the parameters across the 11 carsets :( )
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#124

Post by Michkov »

I still think of GPL as 7 cars and 500 tracks, what can I say :D

As for the usefulness of such granularity, I don't know if putting the effort makes that much difference in the end. The cars already feel different on the brakes as is, with the temperature changes and floating BB they are going to be even more variety. The amount of detail may get lost in all the new effects. My comment was just more of a general musing borne out of curiosity, because I didn't know what the brake setup was for the 67 cars.
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#125

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Michkov wrote: 6 months ago I still think of GPL as 7 cars and 500 tracks, what can I say :D

As for the usefulness of such granularity, I don't know if putting the effort makes that much difference in the end. The cars already feel different on the brakes as is, with the temperature changes and floating BB they are going to be even more variety. The amount of detail may get lost in all the new effects. My comment was just more of a general musing borne out of curiosity, because I didn't know what the brake setup was for the 67 cars.
:mrgreen: I miss the simple days of Coventry and Murasama

I also haven't given it any thought until now! It's interesting to dive into such a topic.

In my opinion, the vast majority of players wouldn't notice the difference, but it would be nice to know each car has its own braking characteristics. I haven't tested this new feature for more than a few laps but the change in brake balance over the course of a few laps is fairly subtle in terms of overall handling, but it is making the brakes feel a tad less predictable. What with the added front-end lift the braking technique has become the polar opposite of what you would do on downforce cars.
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#126

Post by ROOKIE4EVER »

Nice to follow. :thumbsup:

By the way can't login on the new SRMZ and don't receive any mail about it (but well received 2 mails to say SRMZ is online now). :down:
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#127

Post by leon_90 »

PTRACER wrote: 6 months ago At any rate all this presents a good case for rear brakes having poorer cooling than the fronts!
Rear brakes develop less heat than front ones, almost always with some notable exceptions for some front-wheel drive cars. At first the Lotus 49 had ventilated rear disc brakes, but they didn't develop enough heat and cracked, so they replaced them with normal, smaller brake discs.
These guys knew what they were doing, so in my opinion the cooling efficiency should be the same for all teams, at least if we're talking about the '67 season. If anything, having inboard brakes means having an overall more stable car thanks to the reduction in unsprung masses. This is a difference worth highlighting :wink:
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#128

Post by PTRACER »

leon_90 wrote: 4 months ago
PTRACER wrote: 6 months ago At any rate all this presents a good case for rear brakes having poorer cooling than the fronts!
Rear brakes develop less heat than front ones, almost always with some notable exceptions for some front-wheel drive cars. At first the Lotus 49 had ventilated rear disc brakes, but they didn't develop enough heat and cracked, so they replaced them with normal, smaller brake discs.
These guys knew what they were doing, so in my opinion the cooling efficiency should be the same for all teams, at least if we're talking about the '67 season. If anything, having inboard brakes means having an overall more stable car thanks to the reduction in unsprung masses. This is a difference worth highlighting :wink:
Isn't that mainly a brake bias thing? I have the patch programmed to heat the brakes based on bias and pedal pressure, mostly you would be using something like a 54/46 or 52/48 split front to rear, which will heat the fronts up faster. For cooling I'm just copying what Assetto Corsa did, they know more than me :mrgreen:
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#129

Post by leon_90 »

ah yes bb definitely plays an important role, although I imagine that where masses are and which axis is being driven are key factors too. I suspect that the drive axle brakes have an easier time slowing down their respective wheels 'cause engine braking is helping them out, while the other two brakes have to do it all by themselves.
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#130

Post by leon_90 »

This popped up on my social feed today:

Pratt Miller Motorsports
"The front brakes do about 70% of the work to get the Corvette Z06 GT3.R slowed down.
This image is an amazing visual representation of that work in action shown by the intense rotor glow in the front compared to the rear."



Image

In general you can see that rear brakes glow almost always less than front ones. There's a passage in Donohue biography where he tells the story of when he tried to reach the perfect braking balance on the GT40 he shared with Hansgen by (with the help of a friend) making them all glow the same. He would brake at a specific turn, go back to the pits, the friend would tell him what difference there was and he would tweak the car accordingly. The result was that he made it undriveable and Hansgen was very pissed at him :biggrin:
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#131

Post by leon_90 »

Hey Paul, I was watching the video you uploaded about the rain experiment and wondered: would it be possible to implement a 3D model for the flag-waver (s/f) and the track marshall? After that, sourcing and texturing a low poly 3D human wouldn't be too difficult, although it would require someone who can create animations (and that's not easy).
Just throwing the idea :biggrin:
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#132

Post by PTRACER »

@leon_90 Yeah I can imagine every time he stepped on the brakes the rear end came to say hello ;) I'll try to think about how I could implement a greater split between brake temps mathematically, but it would mean a major rewrite (having to shift all the other code forwards to make space).

3D modelled flag waver - That would be very tough, it's not something I could do. I would guess the best way to do it is to create say, 8 different 3D models of a guy waving a flag and then get the game to cycle through them in a loop. But I wouldn't even know where to start. The graphics sections of the EXE are beyond my understanding at the moment.

----------

Small update on this mod. I had a few hours spare on Saturday so I tried to implement a non-linear load sensitivity curve. The test was successful and the feeling was good so I'll add the code officially to the mod at my next opportunity.
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#133

Post by leon_90 »

- Brakes: if I remember correctly from AC, the 312 and Type 49 modelled there have a 100/150 Celsius difference between front and rear, tops. In any case, it's not a crazy difference, although that is because front brakes are always better ventilated than the rear ones otherwise there would be a much bigger difference between the two of course. Honestly, your call mate :biggrin: you have to gauge if there's space for improvement in the current physics model and if that improvement is worth the work you have to put in for it.

- 3D Marshalls: I was thinking of something much, much simpler. Just two different 3D models, one for all of the flag marshalls and flag waver at the start and one for the finish line flag waver. Same thing as it is currently albeit with 2D spinning models. There's no need to implement such a variety, which would only complicate things. We have dealt with the same track marshalls having infinite twin brothers all over the different racetracks of the world for 25 years so I don't think it's too much of a problem to deal with a new family for the next 25 :biggrin: but again, even if you have the time to dig deep into the code and learn new stuff about graphics we would need someone to animate it.
This just popped in my mind: will GPL cope with all of the new polys though? Probably this idea is just a time pit.

- Sensitivity: when you first talked about this I thought of something different. Speed sensitivity for controller inputs, which GPL does not do and makes controls harder on gamepads. I believe that you are talking about something different though, right?
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#134

Post by PTRACER »

@leon_90 Yeah something different:

Speed sensitivity = Reduction of tread grip with speed
Load sensitivity = Reduction of grip with tyre load

SS was not originally simulated in GPL, but some mods include a very simple version in their code. I just replaced that with the calculation used in Assetto Corsa. And LS is already a fundamental part of the tyre physics, I just changed the calculation from a linear to non-linear one. Read the GPL Tyre Model PDF I uploaded and you'll understand;)

Re: Brakes - Indeed :cool: And I spent a lot of time already ensuring temps in AC match the temps in GPL. So if you drive my Lotus 49 and then AC's at Monza67 you'll find the brake temps in both sims hit about 350C at their highest and cool to around 160C at their lowest. Both sims are within 10C of each other or so. Rear brakes don't cool as fast too.

Re: 3D flaggers. That's the problem - there aren't any 3D animation file formats programmed into GPL. Somehow you would have to replace the SRBs with animated 3DOs and you would have to load a new 3DO every frame to animate it. Even if you could do that, I bet it would clip like hell lol
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#135

Post by leon_90 »

PTRACER wrote: 4 months ago there aren't any 3D animation file formats programmed into GPL.
Probably just the driver's arms (and the driver's head thanks to Lee's patch)?
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#136

Post by PTRACER »

leon_90 wrote: 3 months ago
PTRACER wrote: 4 months ago there aren't any 3D animation file formats programmed into GPL.
Probably just the driver's arms (and the driver's head thanks to Lee's patch)?
Good point, though it's not a specific file format. Not sure if there is anything special about the head patch, but driver arms are just another example of mathematics. Each 3DO has an X, Y, Z position. Turning the wheel modifies the X,Y,Z position of the 3DO by a calculated amount. A different calculation is used on the wrists so it gives the impression of the wrists bending. Pressing the Raise Hand button moves the glove's XYZ to another specified location. Same with the gear shift. It's kind of funny how Papy were able to do that back in 1998. Even though the driver hands move in AC, it's just a sequential shifting motion. And the gear stick doesn't move.

Anyway back to the point, I wouldn't know where to begin to make a flag marshall take out a flag, wave his hands in a figure of 8 motion, then put the flag back.
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