Classic British Flight Sim

Hi Chaps,

I've done a little experiment and converted most of my aircraft textures to DXT5. (FSX) I'm finding that the detail is very good and frame rates are much better. I remember trying a similar thing with DXT3 in FS9 and getting results which made the aircraft look like bad AI.

Is DXT5 a higher quality version of DXT3 or is it just something in the way FSX is processing it?

Not tried DXT5.. I presume it's the cut-down version of FSX native .dds :roll: To be brutally honest, a lot of what you see depends on the type and make of card you're using. The 'real' difference between 32-bit and DXT3 isn't such a big deal and conversion is worth 4-5fps in FS9. I'd guess DXT5 is the FSX compat version although DXT3 works too :o

ATB

DaveB :tab:

I noticed when doing repaints for FSX that it uses DDS format which , depending on A/C is OK frame rate wise also....

Tony

From what I can understand DDS is the base format and DXT3 or DXT5 are generated from DDS?

DaveB wrote:Not tried DXT5.. I presume it's the cut-down version of FSX native .dds :roll: To be brutally honest, a lot of what you see depends on the type and make of card you're using. The 'real' difference between 32-bit and DXT3 isn't such a big deal and conversion is worth 4-5fps in FS9. I'd guess DXT5 is the FSX compat version although DXT3 works too :o

ATB

DaveB :tab:

From my understanding DXT5 and DXT3 are identical image quality wise, the difference lies in the alpha channel. They will both compress the physical image to the same quality however the DXT5 will do a far better job with the alpha channel than DXT3. Since in Flight Simulator 99% of the alpha channels aren't very smoothly graduated (we tend to use blocks of very different shades of grey, white and black) you may as well use DXT3. For your average common-or-garden FS texture the original 32 bit bitmap will be 4.0 megs, compressing it to DXT3 or DXT5 will knock it down to 1.0 megs. If you've got a fairly modern graphics card you won't notice any real difference in fps between the DXT compressed texture and the 32 bit version however you will notice a big difference in the moment when you switch views and the textures take a few seconds to "load". However depending on the texture occasionally you will notice artifacts on the DXT compressed version, the vast majority of the time you can get away with it though. On rare occasions you can get away with saving them as DXT1 which will knock the file size down to 512k, however the artifacts can get very messy so it's worth checking. Also remember to always work from a 32 bit master, never open up a DXT compressed file and then re-save it as a DXT compressed file because you'll keep introducing more artifacts and the image quality will get gradually worse and worse.

DDS and DXT are completely different formats. DXT was developed a long time ago by S3 for the Savage GPU and became a widely used format, DDS is Microsoft's own "DirectDraw Surface (hence DDS)" format. Don't ask me to explain the different levels of DDS compression though, I've only just started getting my head around using DDS instead of DXT compressed bitmaps.

Rgr that Chris.

Its very noticeable at airports with lots of AI (all my AI are full models) so the load time is much quicker. I siply ran the Imagetool.exe from the fsx sdk in batch mode (having backed up everything first) and it seems to have helped things greatly.

This might be a daft question, but is there any milage in DXTing ground texture bitmaps? Just curious.

XR219 wrote:Rgr that Chris.

Its very noticeable at airports with lots of AI (all my AI are full models) so the load time is much quicker. I siply ran the Imagetool.exe from the fsx sdk in batch mode (having backed up everything first) and it seems to have helped things greatly.

Indeed, if you left all of your AI textures set at the original 32 bit bitmap (assuming they only use one texture per aircraft and you have twenty aircraft onscreen at a busy airport) you'd be looking at 20 aircraft times 4 megabytes each which gives you 80 megs of textures flying around on just the aircraft. If you compress them to DXT3 you'd only have 20 megs of textures flying around for a minimal quality loss. And if you went further and changed them to DXT1 you'd only have 10 megs of textures flying around.

I tend to keep my own aircraft at the highest quality, i.e 32 bit uncompressed in all it's wonderful glory then (if they aren't already) change my AI to DXT1. AI tends to be of such a detail level that you won't really notice the loss of quality. Of course you don't have that luxury since your AI are full models, but DXT3 is a good compromise.

XR219 wrote:This might be a daft question, but is there any milage in DXTing ground texture bitmaps? Just curious.

I've never tried the ground textures so I'm not sure, but you can get pre-compressed autogen textures on the usual big three flight sim sites where people have simply compressed them to DXT3 or DXT1 which can make a huge difference to your frame rates, or alternatively allow you to have the slider a little higher than you would have had previously.

Hopefully everything I've said above is true; I think it is but I'm sure one of the many talented modellers and repainters on the board will correct me if I'm wrong.

As an aside you can get a .dds plugin for photoshop which makes it quicker to edit the files as you don't have to faff around converting to and from.