Slow JPG decompression

Redfish · Post #1by **Redfish** » 28.08.2002, 14:07

At the moment i'm using large jpg files for the moons of jupiter, but this considerable slows down celestia, even more than loading the earth16k.dds and the satellites surrounding it.
Is there any way to improve the performance?

Darkmiss · Post #2by **Darkmiss** » 28.08.2002, 17:01

I noticed this too
So im trying to get as many dds files as i can

I had an 8k jpg of mars, and it took about 20 seconds to show on the screen, after traveling time.

abiogenesis · Post #3by **abiogenesis** » 28.08.2002, 17:46

You can convert your jpegs to dxt compressed files using utilities created by nVidia. From their website you can download a stand-alone conversion program and a PhotoShop plug-in. The plug-in is, by far, the easier of the two. You just have to open your jpeg in PhotoShop and Save As dds.

The stand-alone program only works on tif files, I believe, so you'll need to be able to do the jpeg/tiff conversion at least. That can be done with The Gimp if you don't have PhotoShop.

- a b i o g e n e s i s -

Rassilon · Post #4by **Rassilon** » 28.08.2002, 20:07

Yeah but has anyone got the dds plugin to work in photoshop?

abiogenesis · Post #5by **abiogenesis** » 28.08.2002, 20:38

I don't know what you mean. I've used it to save files as .dds and that seemed to work fine. I haven't used it extensively and I can't really mess with it now (my GeForce 3 is in the shop

) but I didn't have any obvious problems.

- a b i o g e n e s i s -

Redfish · Post #6by **Redfish** » 28.08.2002, 20:40

Yeah the plugin actually works for me. And making dds files from jpg's did improve speed for me. I couldn't dxt the europa8k texture, cuz it crashed my photoshop.

ANDREA · Post #7by **ANDREA** » 28.08.2002, 22:05

abiogenesis wrote:I don't know what you mean. I've used it to save files as .dds and that seemed to work fine. I haven't used it extensively and I can't really mess with it now (my GeForce 3 is in the shop ) but I didn't have any obvious problems.

- a b i o g e n e s i s -

I have gone to nVidia home page, but I didn't find anywhere the PhotoShop plug-in able to convert .jpg in .dds
Will you please be so kind to give me the web page where I can download it?
Thanks a lot!
Andrea

Ortolan · Post #8by **Ortolan** » 29.08.2002, 01:23

Here you go:
http://developer.nvidia.com/view.asp?IO ... ion_plugin

Miserableman · Post #9by **Miserableman** » 29.08.2002, 11:38

JPGs are slow because they have to be decompressed by the processor before they can be displayed. DDS files also have to be decompressed, but they are decompressed by your graphics hardware, which is a lot quicker and supports some new features.

(at least I think that's right)

Don't use the photoshop plugin (unless you can get it to behave). Photoshop has some bugs involving transparancies which can royally screw your work up. Instead download the standalone tool-suite here. Use the program nvdxt.exe from the command line to convert TIFF files to DDS format. Warning: even though the documentation says it can, nvdxt cannot convert from any other file format than TIFF.

I had to resort to GIMP in Linux to actually make specular reflections in my textures though :O/

Rassilon · Post #10by **Rassilon** » 29.08.2002, 15:06

Miserableman wrote:JPGs are slow because they have to be decompressed by the processor before they can be displayed. DDS files also have to be decompressed, but they are decompressed by your graphics hardware, which is a lot quicker and supports some new features.

(at least I think that's right)

Don't use the photoshop plugin (unless you can get it to behave). Photoshop has some bugs involving transparancies which can royally screw your work up. Instead download the standalone tool-suite here. Use the program nvdxt.exe from the command line to convert TIFF files to DDS format. Warning: even though the documentation says it can, nvdxt cannot convert from any other file format than TIFF.

I had to resort to GIMP in Linux to actually make specular reflections in my textures though :O/

Thank you thats what I was looking for....

Boots · Post #11by **Boots** » 29.08.2002, 22:40

Can any one explain (or point me to) what the differences in the texture formats are DXT1 DXT3 DXT5... and which is best for what type of texture, eg planet, clouds, specular, bump (the latter 2 apear to be greyscale (8bit).

Miserableman · Post #12by **Miserableman** » 29.08.2002, 23:07

A standard picture is made up of three channels - Red, Green and Blue, which makes up the full colour image. Additionally, an image may have one (or sometimes even more than one) alpha channels - a fourth channel that can be used to map the transparancy (think dark = transparent, light = opaque) or specular highlights or somesuch.

dxt1 compression is only for RGB images - no alpha channel

dxt1a compression does have an alpha channel, but it is only one bit, which means there can only be two "colours". A texture such as this might be used to map the reflectiveness of the Earths surface - water reflects, land doesn't.

dxt3 compression supports a full 32bit alpha channel

dxt5 - same as dxt3, there is a difference and I think I once knew what it was, but I've forgotten now :O( I always used dxt3 for my Earth textures, so I wouldn't worry about dxt5.

dxt1 is 8:1 compression, and dxt3/dxt5 4:1 compression. I don't recommend using the photoshop plugin, as photoshop (and seemingly every other Windows program) can't handle transparencies - I had to create my alpha channels in GIMP for Linux (a superb program), then switch back to Windows to sow the dds file together :O/

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