[darwins]

I did post this in a previous thread, but still do not know the answer.

Do we need Levels of Detail in models in OR or does the OR software decide what it draws depending on distance without the need for these?

[ebnertra000]

LODs are almost certainly still required. How else would OR know what should and shouldn't be drawn at a given distance

[darwins]

Just wondered if the drawing was intelligent to think about size and distance.

Possibly as things were further and further from the viewer polys might be omitted, starting with the smallest and then getting progressively larger.

I need to work out what is good practice for OR and what is not as I start to look at building for OR rather than MSTS.

[wacampbell]

Open Rails responds well to having LODs. But there is no need to over do it.

For example if you have a model that renders in a single draw call ( eg 1 texture, 1 material ), and its under about 500 triangles, thats as low as you need to go. There's little value in making a 200 or 100 triangle LOD. It takes modern GPUs about the same amount of time to render 500 triangles as 100 triangles due to their parallel processing.

If you have a model for example, 2000 tris, and 5 draw calls. Then its great if you can add one LOD to get it down to the 500 tris/1 draw call level.

If you are at 10000 tris, then maybe two LODS are in order at 2000 tris and 500 tris

None of this is carved in stone - these guides are just from my own practical experience.

[Genma Saotome]

Right now the correct strategy to follow also depends on the combination of how many instances of the model are placed in the same scene and you've activated instancing. In that case the LOD's are pretty much ignored and all of the placed instances are drawn at once. That does save a lot of work... n models being drawn as-if they were only 1, but the code ignoring their LOD's is counter-intuitive to the model creator.

I agree w/ Wayne's comment that if you can use an LOD to cull one or more drawcalls from a complex model you have an ideal situation for using LOD's.

Last, because of OR's extended view distances models will display at much further distances than in the old MSTS days and there will be a whole lot more models being displayed as well. Recall that few to none of those MSTS models were created with that reality in mind and so with that said I'll suggest there is a legitimate need for more than one or two LOD levels... quite a few polys and drawcalls can be culled from large models in ranges between 2000m and 10000m.

[darwins]

Thanks for the comprehensive answers.

Quote

Right now the correct strategy to follow also depends on the combination of how many instances of the model are placed in the same scene and you've activated instancing.

How do we activate instancing?

Does it work for trains as well as scenery objects?
Presumably if so it would only work for identical shapes - so if we wanted to have a rake of similar carriages with different numbers - then those would presumably be better added as a freight anim. to a common shape...

[Hamza97]

Unfortunately, AFAIK, instancing doesn't work on rolling stock at the moment, so 5 same wagons will be x5 processing only, not x1 processing....

[Guille592]

I have some trains I made myself with way over 40k polygons and more and no LODs on the train. I just simply introduced a distance of 2Km and with a dual core PC I can move it without any hesitation.

[Goku]

Guille592, on 02 February 2018 - 06:23 AM, said:

I have some trains I made myself with way over 40k polygons and more and no LODs on the train. I just simply introduced a distance of 2Km and with a dual core PC I can move it without any hesitation.

If you have only one - two shapes in your activity, then you can ignore LODs. But remember that if you want to use this shape in AI traffic then LOD is very important.

[espee]

If you make a model for yourself, and never intend to release it to the public, don't run it in an activity, don't use it as an AI etc etc and can live with lower frame rates, then you don't need LOD's...