Video tutorial about performance

Tomorrow there will be another online video tutorial on the FSDeveloper LiveStream channel. The subject of this tutorial is performance for 3D objects and the tutorial will start at 22:00 CET (21:00 UTC). The following topics will be covered:

  • Definition of concepts important for the performance: levels of detail, drawcall and texture vertex
  • Performance tips how to make best use of these concepts to optimize your performance
  • Explanation of DXT compression for textures, which types are available and how does the compression work (and what does it do for the quality)

I am almost finished with the preparations, so hope to see you tomorrow for this tutorial!

gPoly status update #6

Today I have been making some progress on gPoly again, so time for another status update. The first part I worked on is the user interface, especially the texture library that contains the texture you can use on your polygons. And also other improvements like the interface used to define new projects.

But most of the time I spend on functionality to import shapefiles. Initially I had not planned this for the first version, but since I had some accurate vector data and imagery of the same airport, this would allow me to verify that the imagery is positioned correctly. As you can see on the screenshot below I think it is quite accurate, since the markings line up very well. So I am happy with that and can move on to some other features tomorrow.

ModelConverterX and LODs

It’s a little bit ironic, after all the effort I put in the LOD Creator functionality of ModelConverterX. But today I found out that the LODs were not really working in FSX SP2 when you exported the FSX MDL files. This is because of the drawcall batching functionality that I wrote about in the previous post. There is a solution for this that breaks the drawcall batching.

So I have now added a new option in ModelConverterX that allows you to specify if you prefer the drawcall batching or working LODs. By default the LODs will be working. If the object has only one level of detail the setting has no influence, in that case the drawcall batching will always work. If the object has animations the setting also has no influence, since these prevent the drawcall batching in any case (and thus the LODs will work).

This fix will be available in the development release of tomorrow. So enjoy your LODs even more from now on!

LODs versus drawcall batching

Since MS introduced the concept of drawcall batching in SP2 of FSX there has been a lot of discussion going on about levels of details still working or not. In the end it comes down to a choice between either having LODs working for your object or having drawcall batching. The MDL files that the GMax gamepack makes will have working LODs by default (and thus no drawcall batching). Since I don’t use 3DS Max I am not sure what the default situation is there. But by compiling with an empty xanim file and the /XANIM flag in XtoMDL you can ensure that your LODs will work.

So this brings us to the choice do we want LODs working or do we want the drawcall batching to work? Today I did some experimentation to try to answer this question. What I did is the following. I made a test object that has three levels of detail, a sphere, a cylinder and a cube. I then compared the performance of a grid of 486 of these objects placed in the situation with LODs working and in the situation with drawcall batching working (but always the most complex LOD showing). And to add another dimension to the test I then varied the amount of triangles in the spheres, cylinders and boxes to see which effect that has. Below you see a screenshot of the test situation.

Sounds complex all this? Let’s take a look at the results I got:

Triangles

Drawcalls

Framerate

744440

486

19

1928448

1

11

 

 

 

435072

486

25

1073088

1

20

 

 

 

259704

486

25

594864

1

26

 

 

 

54456

486

25

139968

1

36

Each row of two results is the situation with a different complexity of the object for the situation with the LODs working (486 drawcalls) and with the drawcall batching working (1 drawcall). So it seems that the conclusion from this is that if you have an object that will be used in many places (many instances) that you are better of without the levels of details, but with the drawcall batching working. Only for complex objects (when more than 600000 triangles are rendered in the scene) it seems that using the levels of detail gets the upper hand again. But I doubt there are many autogen or generic objects that are so complex and placed so often to reach such limits.

I am not completely sure yet what this means for custom objects that are only placed in one or two locations. For those drawcall batching will not bring so many benefits, unless the same material is used on many of those custom objects. So I guess for them using levels of detail to reduce the triangle count is the best choice. But I will try to do some more testing to see if I can verify that.

As I mentioned, these are my first results and I am not sure if the conclusions are correct (yet). So I would be happy to hear your thoughts or ideas about this subject. I have also posted this information on the FSDeveloper forum, so please join the discussion there if you have feedback.

 

ModelConverterX tutorial on Wiki

The ModelConverterX tutorial I gave this evening on the FSDeveloper LiveStream channel, has also been uploaded to the Wiki now. So on both of these places you can now review this tutorial.

Unfortunately I had a few bandwidth problems while recording the tutorial, so I had to restart two times. Sorry for the inconvenience for those who were following the tutorial live. Luckily it seemed there were not so many people watching live. When you watch the tutorial on the Wiki you won’t notice these trouble of course. Another comment I got from Nick halfway through is that the sound volume was maybe a little bit low, I will try to fix that for the next tutorial on Friday, when I will be talking about performance related issues (drawcalls, texture vertices, DXT compression).

Criel-sur-Mer

The last few days we were in Normandy, around Criel-sur-Mer. Just a few days away to relax a bit after a busy year and trying to think as little as possible about work or flight simulation. So when it was a nice and sunny day we decided to go for a walk along the coast and over the beautiful cliffs.

And what do you think we stumbled upon during our walk? A nice little airstrip, on top of the cliff and quite close to the coast. I think the airstrip is used by a local flying club, probably with ultralights, but I am not sure about that. We saw one ultralight flying that day as well.

Apart from a few white markers and the little sign (see the photo to the right) there was not much that identified this piece of grass as an airstrip. I think it must be pretty hard to spot something like this from the air, it really blend well into the environment. I found it back on Google Maps though and you can also see the markers there.

For many FS sceneries it is still a challenge to blend that well into the environment. If there was a nice photo scenery of Normandy for FSX (I am not sure if there is actually, I am not so up-to-date with French sceneries), would this not be a fun little airstrip to fly from while exploring the coast? It could be a nice little side project to make if I ever get bored.

ModelConverterX video tutorial

Just a little reminder that in two days there will be an online video tutorial about ModelConverterX. I think tutorial I will give a quick introduction to the tool and after that I will show how you can use it to convert old API macros into FSX MDL files or how to import them into GMax for further editing.

So you are all invited to join this tutorial on Saturday 2nd of January at 20:00 CET on the FSDeveloper Livestream channel. See you there! And if you can’t make it the tutorial will be available on the Wiki afterwards as well.