Texture Quality

[Pixel Perfect]

Having converted some assets I own from the engine 'I dare not mention' I noticed that the visual quality seemed far worse in Leadwerks and was somewhat taken a back.

 

Having experimented a bit I've come to realise for the first time just what an impact compression and the DTX5 format has on both grain in the diffuse and also the quality of the bump mapping.

 

Once you see it without compression it's hard to go back.

 

Whilst there are I believe some obvious advantages to using compression, namely the ability to fit more textures in the graphics card memory and the fact that DTX expansion is supported in hardware making it fast, I'm not sure I like the side effects.

 

So basically, what are peoples thoughts/experiences on this and what do you use?

[Flexman]

Aye, this was my experience also. When we created the cockpit textures we noticed a huge difference in quality between DTX5 compression and uncompressed. It introduced a purplish hue and grain (bumps) to flat black panel surfaces. As you say the quality is much better without. It left me wondering if there's a texture tool that can achieve a compromise.

 

What we ended up doing was picking choosing which textures to compress and which not to.

[Roland]

Question. Is there actually any meaning to use compressed textures at all, besides hard disk space. Does not of all of them end up in a uncompressed size in the GPU?

[Pixel Perfect]

Thanks Flexman, it's always good to hear other peoples opinions too. I'd kind of come to the same conclusion whilst doing some more conversion, that for things that don't matter so much/are not seen close up I'd probably retain the compression but leave detailed/close inspection surfaces uncompressed.

 

I'm converting some very high quality assets (probably the best I've managed to get my hands on so far) and they really do benefit from not compressing the textures.

 

In answer to your question Roland, it was my understanding that Josh recommended DTX compression for the very reason that it does remain compressed on the graphic card memory; being expanded as required on the fly by hardware acceleration. However, don't quote me on that as I'm just going by what I'd previously heard

[Canardia]

Modern graphics card have 2GB texture memory, so I think there's really no need to compress textures, especially when they look so horrible with DXT5 compression.

[shadmar]

You can use R8G8B8 format to preserve quality.

[Pixel Perfect]

That's what I've been today using. Matches the quality of the png textures used in the 'other' engine. The loss of quality using DTX5 was unacceptable

[shadmar]

Question. Is there actually any meaning to use compressed textures at all, besides hard disk space. Does not of all of them end up in a uncompressed size in the GPU?

 

DDS compressed textures stay compressed in GPU memory, hence the quality loss. So compressed DDS textures actually uses less memory (they don't decompress ==> ultra fast loading). It's the native texture format to GPUs. PNG and JPG textures would need decompression and mipmap generation on the GPU side and would use up to 8 times more memory.

[Pixel Perfect]

DDS compressed textures stay compressed in GPU memory, hence the quality loss. So compressed DDS textures actually uses less memory (they don't decompress ==> ultra fast loading).

From what I've been reading I don't believe that is the case. The drop in quality is purely down to the fact that the compression is lossy, not that they are used without decompression. The articles I've referenced do support the belief that the DDS files are decompressed using hardware on the GPU. They do remain compressed in memory though and hence occupy less space than formats that cannot be decompressed using the hardware, so you can pack more onto the graphics card using direct draw surface formats with block compression.

[Daimour]

I think you are talking about the same but with different words.

 

The articles I've referenced do support the belief that the DDS files are decompressed using hardware on the GPU.

Of course, GPU can't use compressed texture. It need to know color of each pixel with coords X,Y. The main question is when texture will be decompressed? While loading or during pixel colourization? In other words, does it stay compressed or decompressed in video-memory?

 

I didn't read any special articles, but I believe that DDS-textures stay compressed in video-memory and will be decompressed on the fly when needed (may be partially).

[Canardia]

So compressed DDS actually lowers FPS, that's kinda even double worse then:

1) horrible texture quality

2) horribe FPS

[shadmar]

Ah sorry, I haven't reseached it like you guys, my comment was based on the article here

http://wiki.polycount.com/DXT

DXT is widely supported on current graphics hardware, meaning it will stay compressed in video memory

[Road Kill Kenny]

I have 2 personal rules when it comes to textures concerning quality.

 

1. Don't compress normal maps

2. Don't compress anything with alpha.

 

Everything else I compress and there isn't too much of a difference.

[Roland]

I have 2 personal rules when it comes to textures concerning quality.

 

1. Don't compress normal maps

2. Don't compress anything with alpha.

 

Everything else I compress and there isn't too much of a difference.

Yeah.. I think I saw some video by Josh telling "don't compress normal maps" somewhere.

[Road Kill Kenny]

Yeah.. I think I saw some video by Josh telling "don't compress normal maps" somewhere.

 

Yeh that's where I got it from.

[Pixel Perfect]

Will be changing my own stance on this and I'm sure my scenes will look all the better for it. Wish I'd realised this earlier on ... a lot of textures to re-work!