FlightSim Development Group

We received some criticism for unexpected low fps in our FS9 version of Djerba X. The reason is most probably the "scenery shadows" option. Let me explain this a bit:

In FS9 and FSX you can select scenery shadows in the graphics settings. This usually costs a lot of fps - why? The GPU has to calculate everything twice if shadows are rendered. This loss of fps is for most users and developers not acceptable because they want a smooth performance in flightsim.

The easiest solution for the user is obviously to disable the scenery shadows. From community feedback we know that very few FSX users fly with scenery shadows. Because of the usually much better fps in FS9 the number of "shadow pilots" is higher there.

The easiest solution for developers is to simply disable shadows in their scenery addons (hardcode a NoShadow call in the models). This way the user does not have to worry about how to save precious fps. (A lot of developers do this, including flyTampa and other big players.)
Well, it is the easiest way obviously, but surely not the best. If FlightSimulator offers the option "scenery shadows", why take this option away from the user? It's not fair for those who want the shadows for more realism or because they have enough spare PC performance to smoothly fly with shadows enabled. It's just like all the other graphic sliders and options in FS: they're there for a reason! Let the user decide which settings fit him best and develop a scenery that reacts to the user settings.


To cut a long story short:

Our philosophy is: What you select in your FS settings, you will see on the screen. If you want scenery shadows you get them. If you want the maximum number of objects set autogen and scenery sliders to max. If you need more fps disable shadows, reduce autogen or scenery settings and make sure you don't spoil too much performance on things like AI traffic or road traffic (in FSX).

If you have any questions concerning those things don't hesitate to contact us.

Hi Thorsten,

There are several topics on the internet about Alpha Channels. In short, textures without alpha channels can cause performance issues, because the sim has to calculate them on the fly because they are not avalailable in the texture itself. Can you clarify please?

Thanks!

There are in fact no alpha channels for some of the DXT1 textures in the FS9 version, but only few. We will release an update soon that will also include a nice surprise for FSX users.

Whenever there is a surprise is always for FSX users, its unfair, but at the end lets be happy that we are having the scenery

Erik is only slightly correct, the issue with missing alpha channels (Actually its the setting of the Alpha flag within the texture) is in DXT3 textures, not DXT1 because as you rightly state DXT1 is quite happy with or without and alpha.
However DXT3 and DXT5 are certainly not, and you will induce massive stuttering and performance problems with DXT3 and DXT5 with the alpha flag set to none.

If I recall correctly your Djerba scenery had many such DXT3 textures with missing alphas. If you open the textures in imagetool and look on the pane on the right hand side if all is well it will say:
Alpha: Alpha or Colorkey
if however it says
Alpha: None
Then you have a problem.
Note that Imagetool describes the Alpha as being none and this is where we kind of termed it as missing the alpha channel. Techincally its the alpha flag setting within the texture.
Textures created with imagetool that have an all white or no alpha will cause this. DXTBMP will always add an alpha to a DXT3 or DXT5 texture saved with it, regardless of whether the alpha is blank or not.

Anyway, two ways around it:
1) Convert the texture to DXT1
2) Simply open and resave the texture in DXTBMP. DXTBMP will reset the alpha flag and if you reopen it in imagetool it should now show Alpha: Alpha

The following are all DXT3 textures in Djerba that do not "have" an Alpha:
DTTJ_Bld1_lm.bmp
DTTJ_Bld2_lm.bmp
DTTJ_Bld3_lm.bmp
DTTJ_Bld4_lm.bmp
DTTJ_Bld5_lm.bmp
DTTJ_Detail_Grass.bmp
DTTJ_FireStation_lm.bmp
DTTJ_Gate_lm.bmp
DTTJ_LightPoles_lm.bmp
DTTJ_MainTer1_lm.bmp
DTTJ_MainTer2_lm.bmp
DTTJ_MainTer3_lm.bmp
DTTJ_MainTer4_lm.bmp
DTTJ_MainTer5_lm.bmp
DTTJ_MainTer7_lm.bmp
DTTJ_ParkingArea_Surfaces.bmp
DTTJ_ParkingArea_Surfaces_lm.bmp
DTTJ_StairBody_lm.bmp
DTTJ_Twr2_lm.bmp

This I am almost certain is the cause of performance problems. Fixing these textures should give you nice, smooth performance

Regards
Garry

Thanks for the explanation Garry! Indeed I only look at the DXT3 textures.

Garry, I appreciate your input, but I do not expect that this will change anything for FS9 users. In FS9 DXT1 is used whenever you do not need an alpha channel. If you do (because of transparency) you use DXT3. So in FS9 all DXT3 textures do have an alpha channel.

Now for FSX the story is completely different, because FSX does not know DXT1 and internally converts DXT1 to DXT3. So no need to feed DXT1 textures to FSX in the first place.
Secondly those stutters were only reported for FS9, not FSX. I have also no reports of FSX having any trouble with DXT3 -alpha textures.

Thorsten I'm talking about the FS9 product.

Using your installer there are nineteen textures that are DXT3 without alpha channel, you are simply not correct in saying that all your FS9 DXT3 textures have alpha's - they do not.

Go ahead, run the installer and then open the textures I listed in imagetool. I'll bet you anything they show Alpha: None
I'm not really sure what else to say, if you are arguing that I am wrong and these textures do have alpha's then repectfully thats just not the case. A clean, fresh install has nineteen of them as listed in my last message.

Please do not bring DXT1 into the discussion, this is not about them. Yes you have them in your Djerba scenery and of course DXT1 without alpha is perfectly acceptable, there is no performance hit. However this is not the case with DXT3 without alpha and THAT is the point of this discussion.

This is only about DXT3 textures in your Djerba product that are missing Alpha channels and they are there.

Garry, thanks for the feedback. I am in fact surprised to see that there are quite some DXT3 textures that should not be DXT1 at all. No idea why a) we didn't notice and b) they ended up in the final release anyway. Maybe just a stupid mistake when we packed the 1.1 update.
I agree that those DXT3 - alpha are indeed a bad thing and should not be DXT3. I was just not aware of them.

No problem, glad we got there in the end Happy to help.

Its unfortunate that almost every addon scenery still contains there textures and from even large, respected developers like FSDT, LatinVFR, Aerosoft, UK2000 so its by no means unusual ;)

There is an incredibly useful utility called Alpha searcher made by the World of AI guru Peter VanderVeen that makes finding these problem textures a breeze. As far as I know Peter only made it available to us at the Alpha India Group forums (registration needed)
http://www.alpha-india.net/forums/index ... 5#msg92195

It finds these problem DXT3 textures quickly and easily. Its the first thing I run after installing a new scenery

For users I would suggest checking other sceneries, because there are loads of these suckers out there, and the fix while time consuming is very easy.
As I posted two fixes
a) Convert the problem textures to DXT1 instead of DXT3
b) Open the texture in DXTBMP and do nothing more than save it again as DXT3. DXTBMP will "add" back the alpha channel

Some people are concerned with the quality reduction of DXT1 so option b is better for them. Personally I am quite happy with DXT1 so I use option a.

Hope this has been helpful
Regards
Garry

We usually only use DXT3 in FS9 if we need the alpha, so I'm at a loss of explaining how those files ended up there. That tool will certainly help making sure that kind of thing does not happen again.

atco wrote:No problem, glad we got there in the end Happy to help.

Its unfortunate that almost every addon scenery still contains there textures and from even large, respected developers like FSDT, LatinVFR, Aerosoft, UK2000 so its by no means unusual ;)

There is an incredibly useful utility called Alpha searcher made by the World of AI guru Peter VanderVeen that makes finding these problem textures a breeze. As far as I know Peter only made it available to us at the Alpha India Group forums (registration needed)
http://www.alpha-india.net/forums/index ... 5#msg92195

It finds these problem DXT3 textures quickly and easily. Its the first thing I run after installing a new scenery

For users I would suggest checking other sceneries, because there are loads of these suckers out there, and the fix while time consuming is very easy.
As I posted two fixes
a) Convert the problem textures to DXT1 instead of DXT3
b) Open the texture in DXTBMP and do nothing more than save it again as DXT3. DXTBMP will "add" back the alpha channel

Some people are concerned with the quality reduction of DXT1 so option b is better for them. Personally I am quite happy with DXT1 so I use option a.

Hope this has been helpful
Regards
Garry

Helpful! helpful!? .....this is the find of the year for me! thankyou very much.

I have just "fixed" the alphas on Aerosoft's Maastricht scenery..... now loads faster and smooth.

Garry, I don't find any DXT3 textures without alpha in our V1.10, I guess you didn't install the update?