11 replies to this topic

[Siddley]

For race sims I mean - I tried it....it's not that easy...

I started a project to build a replica Porsche 908 - a real vehicle - and modelled it in Solidworks. My friend was a very skilled fibreglass laminator, he built racing boats so he was going to make the body for me, and I thought the tubular chassis shouldn't be too big a problem as I used to build custom bike frames. A spaceframe is just like a bike frame, except bigger ?

What I really wanted to build was a 917 ( I saw the movie 'Le Mans' one too many times ) but I couldn't figure out a way to mold the windscreen, so 908 Spyder it was.
I bought an MoT failure Lexus with a good V-8 engine as the powerplant, but then we emigrated to Spain, killing the project.
This is the Solidworks model :-

 

Then I showed it to the HistorX guys and they asked me to model the 908 for their rFactor mod.
That was a real eye opener. Solidworks will only allow you to construct a shape which can exist in the real world rather than on a computer screen and it's not good at surfaces anyway. At least not the kind which form the body of a 908..

I had to use 3D Max, which lets you do what the hell you want because it's not engineering CAD, it's just for video games and stuff. So I thought it would be easy. Big mistake. It wasn't the modelling ( which was kind of alien to me at first, because it's got no engineering basis ) but the challenge of producing a model which wouldn't have so many polygons\vertices that it would fry any video card trying to reproduce it.

Eventually I got to this :-

 

It drove me bananas getting there because all the time you have to be reducing the polygon count without making the poor 908 look like it was built from triangles and flat planes. And then, even worse, you have to texture it so that it can have a 'skin' wrapped around it with the livery.
Real life again got in the way, so it was never finished. Then a hard disk crash lost all the files, which I would have turned over to the team for them to finish...

So I take my hat off to 3D modellers for race sims , that stuff is not as easy as it might look...

Edited by Siddley, 29 March 2014 - 00:15.

[Radion]

Looking not bad!

I also model since a year or so, just for kicks. It's real fun to play around with the polys and design your own car. The biggest challenge though's to find decent blueprints. I wasn't able to find any (I gues you too used blueprints?), so I used the ones that the FIA has in their rulebook and went from there. Anyway, I never finished the project. At one point, I just lost interest (hence some 'flaws'). 

 

 

I used cinema4d for this. Not sure how many polys, I think too many for any video card/game engine... 

Edited by Radion, 29 March 2014 - 15:54.

[Siddley]

Wow, that's pretty good but a lot too many polys for a game I reckon...with rFactor at least the graphics engine applies smoothing to the model and what you create is a model that looks a little crude, but when shown in game looks much better.

What I did for the 908 blueprints went like this. I found a general arrangement drawing of the 917 spaceframe and suspension, which I reverse engineered into a Solidworks 3D model ( I still think I'm building a real car here, and designing my own suspension geometry is way beyond my skills )
Then I used 3 view drawings from a web archive of 1960's slot car magazines to create the 908 body and scaled it slightly to fit the 917's wheelbase and track. Then I tweaked the 908 shape using photographs. A lot of photographs...

When I had given up on the real 908 project and was using 3D Max to make the virtual 908 for HistorX the body was inherited from the Solidworks model, using a really awkward process to convert it to .3DS which involved about 3 different changes of file format. The spaceframe didn't make it over as most of it would have been invisible and just added polygons.

If you are modelling modern cars I think blueprints are going to be a huge challenge. For anything pre 1970 there is the slot car magazine archive ( the name of which I forget ) which is pretty good. As far as I can figure out their technical illustrator attended race meetings and measured the cars. What a lousy job to have

A modern F1 car I'd guess would be the biggest challenge of all, given the level of secrecy that goes along with anything aerodynamic.
There was a car modelling forum I used to use ( mainly just reading it, rather than contributing ) which had a blueprints section, I can't remember the name  and I have a feeling it may now be defunct.

[RogerGraham]

Siddley and Radion, how many polys are roughly in each of your models?

[Siddley]

Helpfully enough, I can't answer that Roger

 

The Solidworks model doesn't have polygons as such, it doesn't use wireframe methods to construct surfaces. If you had an enormous 5 axis milling machine and a huge block of plastic or aluminium you could put the file through a post processor which outputs G-Code and eventually the machine would spit out a full size 908 body. Theoretically anyway...

What you see there is output from Solidworks buit in rendering engine.

The 3DS wireframe in the screenshot was something like the target poly count that the mod team aimed for. What that was I can't remember of course...
When I initially converted the Solidworks model to a 3DS wireframe it almost made my PC drop a valve, such were the number of polys. 3D Max has a built in poly reduction tool, which I ran a lot of iterations of, and then reduced polys by hand - vertex by vertex - because if you use the tool too aggressively it messes up fine details. A lot of work.

So there you go - some useless information and no answer to your question

Edit :- One issue with building 3D models for racing sims, assuming you don't have a large budget ( in the case of most mod teams that means no budget at all ) or access to the real cars is that the question " which cars do we have enough research material on to model ? " becomes a lot more important than " which cars would we like to model ? "
Which sort of fits in with the discussion we had about the Project Cars list of vehicles...

Edited by Siddley, 29 March 2014 - 15:10.

[Radion]

Siddley and Radion, how many polys are roughly in each of your models?

The basic model has ~6000 polys. The final one (as you can see in the pic above) has ~37000 polys.

 

Edit :- One issue with building 3D models for racing sims, assuming you don't have a large budget ( in the case of most mod teams that means no budget at all ) or access to the real cars is that the question " which cars do we have enough research material on to model ? " becomes a lot more important than " which cars would we like to model ? "

Which sort of fits in with the discussion we had about the Project Cars list of vehicles...

Good point. 

I think the big studios get access to some data from the teams in order to be able to replicate cars as realistically as possible. Which of course's in the best interest of the manufacturers. Would love to actually see the whole process of creating a formula one model from scratch. 

Btw Siddley, max should also have an option that allows you to view the amount of polys of your model?!

[Siddley]

Btw Siddley, max should also have an option that allows you to view the amount of polys of your model?!

It does and it gave me nightmares when modelling the 908

But I don't remember what the amount was, this all happened nearly 5 years ago and I lost the original files.

I wonder if the F1 licenced cars are provided by the teams as 3D models to the software developer ? with the shapes simplified so they aren't giving away any of their aero secrets...

[RogerGraham]

Hi Radion, apologies if you've already seen this (and it's not an F1 car), but here's a video on how iRacing prepared the 2014 BMW Z4 GT3.

 

Hi Siddley, just on your thought that maybe the models had too many polys for a game.  I only have figures for Project CARS, but other new games running on the same hardware probably target similar polygon counts, depending on whether they emphasise the cars or the tracks etc.

 

For Medium graphics settings, the poly counts and LOD distances are:

 

LODX = 200k - (mainly for GUI)

LODA = 50k - High detail LOD (0-10 meter)

LODB = 20k - Mid distance LOD (10-60 meter)

LODC = <2k - Far distance LOD (60-500 meter)

Cockpit = 50k - 1st person cockpit (basically same detail level as LODX, but optimized for game use)

 

The High and Ultra car detail settings double the LOD distances, and the Low setting halves them.  I believe that Ultra graphics settings now use LODX for cars that are very close to you.

Edited by RogerGraham, 04 April 2014 - 14:32.

[Siddley]

I wish I could remember more about the 3DS model... I seem to recall that with rFactor some LOD changes were built into the game and some had to be taken care of by the modeller. I'd actually got to the point of readying it for texture mapping when we suddenly decided to move 1000 miles to a new country and live on a smallholding in the middle of nowhere.

 

I REALLY wish I'd still got the Solidworks model of the 908 chassis and body - I showed it on a forum dedicated to people who build real world replicas of sports prototypes and even though I haven't even looked at the forum for 5 years I still occasionally get emails from people offering me money for it. The last sum mentioned was $500...
One guy who contacted me was a graphic artist who was drawing a comic book about the 1970 WSC season. He didn't have any money to spend but wanted the model as a reference. I would have helped him out gladly, the guy is very talented and the subject is very close to my heart.

But I didn't back my work up, and a dual boot utility wrecked my hard drive. Mostly my own stupid fault

[Radion]

@RogerGraham: Awesome stuff, thanks for that!

[gilez]

Looks sweet! I'm a total ignorant on the matter but i'd love to drive that in Assetto Corsa! Maybe you can check their forum too, they seem to have a good modding community.
http://www.assettoco...ins-modding.24/
Hope you can make it!

[Siddley]

I could model the 908 again, but someone would have to pay me a lot of money to do it