File formats for textures
polycounter lvl 3
Why .exr is not used in games ? Instead people go with targa?
Some say file size is smaller some say bigger compared to png
Also why targa is used instead of png ? Only reason is alpha channel ?
Some say file size is smaller some say bigger compared to png
Also why targa is used instead of png ? Only reason is alpha channel ?
Replies
What the image is storing.
How easy is it to generate.
Compared to PNG and TGA, EXR can store higher bit depth images because colour is stored in 32bit floating point, but even then RAW and HDR have you covered for most cases like landscapes and HDRI's.
What features of EXR are you interested in? If it's just a size thing, I'd be curious what was said. You might have read something like: "One EXR image with all my layers is smaller than several PNGs of my layers" which could be true, but probably isn't true about a single image. Or are we talking about how a VW Camper Van can overtake a Ferrari if the Ferrari is only doing 30mph? (Not that I'm saying a PNG is a Ferrari)
Png alpha support is shit in Photoshop but that's easily avoided by eliminating Photoshop from your pipeline.
Exr support in substance designer is basic but functional - you can't do deep images but that has limited utility in game development and beyond that the only trouble I've had is with zbrush (and that is because zbrush is a dick)
It's perfectly fine fine for up to 4 channel 32 and 16 bit data
as gnoop says deep exr is the logical place to go - it was designed for use in vfx pipelines where there was a need to package up multiple images per frame for compositing (exactly was we need for shaders).
It supports any number of channels which don't need to all be same resolution (i think precision can vary between channels too but would have to check ) and is open source.
The downsides are mainly around tool support since the python libraries are all written for Linux and believe me it's a pig to build for windows
For doing VFX, or transport between various software packages I completely agree that EXR is the best way to go. However, If you're taking it to a game engine then you're not gaining anything by choosing EXR really. The thought of a file format with great tool support that carried all your PBR channels in one file is nice for organisational purposes, but at some point you have to separate them into different formats (greyscale, rgb, rgba, bit depth and custom compression settings) to sample them in the shader at which point it's just as logical to import them individually.
That's before you get to the bit-depth issue, I thought EXR might be able to store more than just 32bit float but after searching I realised all it can do is 16bit float, 32bit float and 32bit int (that's per channel, i.e. 0 to 4,294,967,296 values of colour). That's a massive amount of colour range, most people don't need all that for hero assets let alone game props. Even 16bit int is overkill outside of normal and height maps (at SDR). So now we just move the problem and say "that's okay the engine will just optimise" but that defeats the point of using them, since we are now reducing the quality of them intentionally and we have to manage that ourselves because we're artists and we're fussy bastards.
These days everything's getting a live-link plugin anyway and that's ideal because it means we don't need to worry about it anymore, let the developers work out what you need and organise it for you silently.
I'm not entirely with you on bit depth
More precision going into a process such as compression can and often does improve the quality of the output and of course it comes into play if you're switching colorspaces or compositing textures between export and compiling into your engine.
Given how easy it is to produce 16bpp texture data I don't see any downsides to doing it - as long as you're not working on unreal