vertices or textures?

[robystar]

Hi,

Guess this is a basic question but I still have my doubts as to what is best:
Working on a (real life resembling) fire station that is not too complicated as far as textures go, but rather big as the number of vertices go, I simply wonder if it would be a better idea to cut down on vertiices or to use more different kinds of textures.
I could save a lot of polygons by using textures with an alpha channel but I would have to reposition and rotate those textures and have different alpha channels, especially if I want to add nice night textures as well.
I include the skp file of my (non finished) model to show you what I mean.
Your comments appreciated beforehand,

Thanks,

Roby

 

[kevintampa5]

I would just make a shell since no1 will ever be inside. erase as many un-needed lines and faces as possible. You can use LODs to accomplish this as well.

see image

 

[hcornea]

The answer is "Materials"

The lowest number of materials that will do the job is what is required.

There is a caveat (or two) ... for example, roof textures shared with other parts of the airport can share a common material (and hence drawcall) to save texture space. There are some clever ways of doing this to save space, and increase performace.

In an ideal FSX model, you would use:

1. a single material for the entire model (and hence a single texture)
2. < 65535 tVerts
3. don't use LODs

You will then use one drawcall, and hence one buffer in the video card. If you use LODs, you will not benefit from drawcall batching performance gains, and really the object is not "that" complex as to need them.'
In FS9 the optimisation considerations will be different.

 

[robystar]

Hi,

- Thanks but I was still going to delete the superfluous lines. The basic question is whether to use many different textures with alpha channels instead of making the wall 3D (see image) and have a lot more polygons.
- I also would opt for the extra polygons and keep the materials down to two or three, but that is only a gut feeling and not based on comparisons. Appreciated your explaining the reasons.
Am I wrong or am I getting conflicting advice?

Roby

 

[hcornea]

Yes ... you are getting conflicting advice, so you'll just have to work out which is correct.

 

[kevintampa5]

Yes ... you are getting conflicting advice, so you'll just have to work out which is correct.

I am not conflicting I am offering additional ideas. I would assume you are going to make a number of more models for this project. Not just one. Which is where my point of view came from.

Its really a matter of what you feel like doing. Both methods seem to work and have their limitations, such as the Drawcall with LOD limits. Drawcalls are great, LODs are great, just depends on what you want to accomplish.
Certain things will always yield similar results and that is what Hcornea is suggesting. The results would be predictable, but may not be as easy.
Results that I offer would be predictable, but may not be as easy either.

As for verticies vs texture, I have encountered fewer problems when using more textures rather than more faces. I have a large set of models which do not really affect performance even without messing with LOD or Drawcalls. My models incorporate single face with texture in most cases. The single image/texture to give the appearance of more detail appears to render better as far as performance goes. Having 50 or so textures for multiple models is great when its all on one texture sheet. Now if each texture was being rendered from separate files, you could have performance issues if the textures are large enough and numerous enough, this is when more faces would not affect as much in performance. The only issue with vertecies I have is the compiler limitations. That one still hits me in FS9 - and when it does I have to break the models down. This is easily done if you set up layers in Sketchup. FSX havent had the same issues with compiler, but I still work it the same way.

Although there are multiple ways to do this, the best way is to be determined by the author, as you have to do the work. The easiest method and most efficient performance wise is all up to you.

On a side note to the above discussions, I have seen amazing GMAX scenery for Philippines that hit the frames hard because of all the textures loading from separate files. I have seen scenery from the same region that used texture mapping and it was almost non-noticeable. At the same time, had GMAX kmia scenery, terrible frames, very few textures because it was compounded sheeting, the models had so many faces it hurt the frames. Had a different scenery same airport, GMAX as well, had very clean models along with texture sheeting gave beautiful performance. Only hit 1 or 2 max on the FPs.

All machines are different, and that does make a difference. What hurts my frame rates, may not affect HCornea's. Settings and hardware make all the difference.

 

[hcornea]

Kevin,

With all due respect, I am speaking from experience developing and publishing scenery which encompasses a small town and airfield in "quite a bit" of detail.

The scenery has been sold and used by a large number of FS users on the variety of machines they use. Not just tested and run on my computer.

The basic principles hold, regardless of what machine you are running, if you are developing for FSX SP2.

And no, the performance using LODs as opposed to drawcall batching are not even close. Of course, mdls exported from gMax do not support drawcall batching without modification.

LODs have their uses, but rarely is the model complexity sufficiently high that they offer better performance.

In the case of the GSU model posted here .... LODs will offer worse performance. I would almost guarantee it.

3340 tverts = not even close to a single buffer.

LODs will slow texture loading, slow rendering, and inhibit drawcall batch-draw operations.

 

[robystar]

Hi,

Thanks for all the info.
Maybe I should point out that I am on FSX sp2 and uptil now none of my buildings has given me much impact on the fps except for those that used a lot of different textures. But I always thought that was because of my low end computer (intel D915, 2Gb RAM, Nvidia 7300SE).
However, none are deteriorating my fps as much as autogen does.
So, I guess I will follow Hairy's advice, keep the materials to a minimum (think there are going to be five different ones in the end, of which two will be bumpmapped), and draw the other building at the side in the same way including all the hurricane shutter vertices needed.
And yes, Kevin, of course there are more buildings modeled on this airport (like the terminal with 130,000 texture vertices and some 30 textures, something which I still have to have a look at because it seems a bit too much).
I do still have 15 fps (locked at 20) on my obsolete rig.

Roby