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arno

DXT1 - Lack in image quality after converting?

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Hello Guys,I'm just creating some large scaled textures of 1024x1024pix size. When I use PhotoImpact for converting them from 24bit to 8-bit, all works very well and there is no real difference visible.But when I use ImageTool to convert the same texture (doesn't matter if from 24-bot or 8-bit) to DXT1, there is a real lack in quality.Is is not possible to get the same result with DXT1 as with 8-bit BMP? Or are there any hints and tricks to get better results?Best regards,Sasa

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Hi Sasa,I have never seen a big difference after converting to DXT1 (DXT1 is 16 bit, so converting to 8bit first is not really useful). What do you mean with a low quality? Does the image look blurred or so? In that case it could also be that the highest mipmap is not shown on time.

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Hi Arno,Well, 8bit looks definetely better than DXT1 converted from 24bit. Just have a look at the Attachement above.I've never seen it that much before, but the bitmap converted there is quite large and has many colours in the grey range.Sascha

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Hi,I use convr8 program for converting 24 bit to 8 bit.I red that DXT1 is rather for simple things. And that DXT3 gives more detail. Right ?Greetz. Jos

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Hello Sascha,In order to see the best quality display of textures, it is necessary to place FS settings to the maximum.Please go to Options - Display - Hardware tab, and put the Mipmap slider to maximum (8).Best regards.Luis

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>In order to see the best quality display of textures, it is necessary >to place FS settings to the maximum.That won't help. The reduced image quality is already visible in ImageTool after converting.>I use convr8 program for converting 24 bit to 8 bit.R8? Isn't that FS5-style with 256 fixed colours?! ;)>I red that DXT1 is rather for simple things. And that DXT3 gives more >detail. Right ?DXT3 gives more detail for partly opaque/transparent parts of the image. But it doen't help to get better quality with it for all I know.Best regards,Sascha

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Hi Luis,>Please go to Options - Display - Hardware tab, and put the>Mipmap slider to maximum (8).I don't think this option does that much. I have set it to 5 or 6 in general, when you set it to 8 the terrain texture don't look nice anymore, because the highest mips are shown too far away (gives a bit of a blinking view).But on the same settings page there is also an option for the texture size (at the bottom). Setting that to massive is necesairy to see the 1024x1024 mip of any texture.Sasa, do you also have mipmaps in your 8bit image? I am thinking it could be a wrong texture scale in your GMax object. Causing the wrong mipmap to be displayed.

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Hi Jose,>I use convr8 program for converting 24 bit to 8 bit.>I red that DXT1 is rather for simple things. And that DXT3>gives more detail. Right ?No, the only difference between DXT1 and DXT3 is the size of the alpha channel. With DXT1 you can only have black and white in the alpha channel (so only fully transparant or not), while DXT3 allows you to use grayscales as well, so that you can have more levels of transparancy.

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Hello Arno,Please notice the trees in the images. This is with Mipmaps set to 4:http://forums.avsim.net/user_files/117336.jpgAnd here is the same view with Mipmaps to the maximum, 8:http://forums.avsim.net/user_files/117337.jpgAs you can see, the difference is quite noticeable. The virtual cockpit is also using DXT-compressed textures, as well as the gauges, and here also you can see a lot of difference in the quality.Best regards.Luis

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Hi Luis,That shows quite some difference indeed. But don't you find that the landscape looks to "noisy" when you fly around with this mipmap setting? Or maybe that is a personal taste as well.I guess when you get closer with the mipmap setting at a lower value, the more details mip will still show? It is just the time at which it shows that differs I guess.

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>Sasa, do you also have mipmaps in your 8bit image? I am thinking it >could be a wrong texture scale in your GMax object. Causing the wrong >mipmap to be displayed.It doesn't matter if I use mipmaps or not. After converting there is a real difference visible. If you like, I will send you the sample image (approx. 2-3MB, 24bit) by mail.Sascha

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Hi Sascha,Sure, I am certainly interested to take a look at it.

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Hi Sascha,I took a look at the texture and there is indeed a small difference in the quality of the textures. This must be due to the compression that is added to the DXT texture.But I also made two test cubes in GMax and placed the two textures on them (one 16 bit (555) and one DXT1 texture). And I must say that you hardly see the problem in that case. Only when you are really close (witin a few meters or so) I find the difference really noticeable. And I guess when you don't know the difference, you would not even find the DXT texture looking bad.

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Thanks Arno! :)Well, when you're 100 meters away from the object you may not notice it. But these object is a hangar und usually you would get close to it.So on the one hand you have to option to get worse results with DXT1 and save around 30% of texture size. On the other hand you can get the best results with 30% more texture size.I guess with the new computer systems that won't make a big difference anymore.Sascha

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Hi Sascha,Yes, I think that is about the choice. Either you have a 700 kB DXT texture, or you have a 2 MB texture that is not compressed.The DXT format should also be processed slightly faster by the graphical card and thus improve the framerate a bit (altough I have never seen a huge difference).So I think for most objects a DXT texture works fine, but when you want very very high detail, using a non-compressed format is better indeed.

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