LOD stories.. and a query - Need Help for LODs setup

Chris · Post by **Chris** » 22 Jul 2007, 18:36

First of all, relax and get a cup of coffee or get back some other time - Yeah, I know, Greeks are talking too much

Well, I have a query for the F-16 block 52 plus I'm trying to build - you can see some pictures in the "your packages" section. I'm writing this query here as it is not directly related with my project but it might be helpful also for other people. This query might be stupid for somebody but I have to do it anyway.

For the records I'm still on the 30 percent of the design progress.

Backround

Well, as I have described in the other section, it looks like the last upgrade into my pc was powerful enough so I cannot test anymore my model correctly

With only the LOD 1 - 6000 polys - without textures applied - not armed, according to ACM I'm still getting 30-60 fps on an empty airport - I mean without any other facilities and 30 aircrafts parked on it. Usually I have some 35 to 45 fps. When I'm turning my view to the opposite side so as to hide all models the fps are again 40 to 60 even to 80. For the records for FS9 I have set the fps slider to unlimited.

So, as a result I cannot figure out anymore what impact this model will have on lower end machines and I cannot set correctly the LODs

Ok, with over 30 fps the first answer I gave to myself was - I don't need LOD models

Just kidding!

Now let's come to the hot part..

Some time ago, after I saw a relevant article in the freeflightdesign.com, I bought the 3D action reducer, which to those who are not aware, is a tool for reducing polygones by moving a slider - works with 3ds and x - and If you are not carefull you can destroy very easyly your model. Convertion and reconversion proccess from FSDS V3 is simple using CVA converter and 3d exploration. Please dont' ask for more info - I'm not advertising this software - If you are interested Just google it

After a quick attempt (10 minutes total including makemdl process) I ended with 11 LODs by reducing the polys by aroung 500 every time. LOD 400 = 6000, LOD 350 = 5500 and so on and the result was good enough - at least to my eyes

So, my query is to the designers and their experience from testing - particulary those using not high end machines is:

Based on the fact that I will probably end this model at 8000 polys (for the time being) I have accepted already the fact that the polys for LOD 1 are too high

How many LODs would be considered as appropriate and how many polys should I cut on each step i.e. LOD 1 6000 polys to LOD 2 5500 polys = 600 polys. This off course might not be the same for all cases i.e. LOD 1 to LOD 2 1500 polys, LOD 2 to LOD 3 800 polys.

I know that probably there is no easy answer to be given and there is a lot of testing required but I'm sure I have many things to learn

I would be grateful to anyone can help me on this issue.

Thank you in advance and sorry if this was time consuming to you.

Chris

nickblack423 · Post by **nickblack423** » 23 Jul 2007, 14:31

Chris

For my models I do 7 LODs now, but for a higher model you may want to go up to 8. Make them 400, 300, 200, 100, 075, 050, 015 and 005.

The way I test initially is to copy the main LOD1 into all the LODs and make a small coloured box floating next to the aircraft, so that in FS you can see when the transitions change, to judge where you need to lose aerials etc.

When making my LODs I start by copying the main model into LOD200 and lose the aerials. Then copy that into LOD100 and make the wings/tail into flat shapes. And gradually lose detail in further models. Im sure you've got your own way of doing that by now though.

I reckon you need to aim for no more than 5000 polys on the main LOD1 though, and if you're gonna do that you need to make sure the lower LODs are very low poly in order to counter the high polys of higher LODs.

Hope this helps.

Nick

Chris · Post by **Chris** » 23 Jul 2007, 16:38

Thank you Nick, I appreciate your help

,

So, as I'm thinking how to catch what you are describing and If I understand correctly the concept, my target should be

a. To reduce the LOD 1 polys as possible but at least to below 5000.

Ok, practicly that means that I will have probably to redesign completely the fuselage and the vertical stab so as to be more efficient. No problem with that apart from the fact that I'm afraid a little, since I'm not experienced, not to destroy the shape. So, ok I'll give it a try

b. After let say the LOD 1 is ready, I have to create about 8 LODs in the pattern you have described i.e 400, 300, 200, 100, 075, 050, 015 and 005.

c. Indepentently of the method that I will follow to reduce the polys between LODs, in order to keep a good balance, when the LOD 1 is about 5000 polys, I will have to reduce the polys between LODs at about 1000 polys every time and at the same time to keep the last 3? LODs with very little polys i.e. LOD 6= 500, LOD 7=200 and LOD 8= 100 or less.

Is that right? If you find some time please correct me if and where wrong

Thanks again Nick

Chris

nickblack423 · Post by **nickblack423** » 23 Jul 2007, 17:03

I dont usually have a guide to the amount of polys in each LOD, I just see what I can get rid of in each level. Some things I do are like,

Changing the wheels for less sided models lower down. Changing the Gear for less sided tube lower down.

Tips Ive found for reducing the amount of polys on your main LOD1, is to make surfaces 2D where you can, like gear doors and aerials etc.

Nick

Chris · Post by **Chris** » 23 Jul 2007, 17:56

Ok, I can see clearly what you mean. So, is much more a matter of judgement for each LOD what to keep and what not to keep considering also 2D surfaces where possible in long distances. I'm going back to FSDS for testing..

Thanks again

Chris

nickblack423 · Post by **nickblack423** » 24 Jul 2007, 07:27

Yeh it definately is a matter of judgement. There are no hard and fast rules. Unfortunately for fighters there are so many small things that are noticed when they dissappear, aerials etc.

Ive just been looking at your model. It looks fantastic, you've done a great job there. Unfortunately it may be too intricate for a useable good AI low-poly model. When building these you need to make a big choice between top-quality and low-poly. You'll end up with lots of simpler shapes that maybe arent as round as you want, but as long as they look the part they'll be good. remember most people looking at AI are seeing it from a distance anyway, not mega close up. Use textures where you can to show things rather than modelling them. Take my B2, I didnt model the engine exhaust, instead just used a texture to show where they are. Same principles could be applied to your F-16 mate.

All the best with it, lets see it out soon.

Nick

Chris · Post by **Chris** » 24 Jul 2007, 07:51

Thanks Nick, You are very kind and your input is always valuable

Ok, I'm having some tips in my mind and yesterday I took the big decision. After testing some ideas I had about it, I found that there is a strong possibility - fingers crossed - to keep almost the same appearance as my pictures are shown with 2000-2500 less polys... This will bring the LOD1 to 4000-4500 polys. Of course it is too early and I have to spent many manhours which I don't get easily...but the decision has been taken already. I have this week off work so I'll try to speed up a little..

I'll get back when I have something positive on this.

Thank you

Chris