You can’t even imagine how hard it was to release luminance-0.7. I came accross several difficulties I had to spend a lot of time on but finally, here it is. I made a lot of changes for that very special release, and I have a lot to say about it!
As for all my projects, I always provide people with a changelog. The 0.7 release is a major release (read as: it was a major increment). I think it’s good to tell people what’s new, but it should be mandatory to warn them about what has changed so that they can directly jump to their code and spot the uses of the deprecated / changed interface.
Anyway, you’ll find patch, minor and major changes in luminance-0.7. I’ll describe them in order.
Internal architecture and debugging
A lot of code was reviewed internally. You don’t have to worry about that. However, there’s a new
cool thing that was added internally. It could have been marked as a minor change but it’s not
supposed to be used by common people – you can use it via a flag if you use
though. It’s about debugging the OpenGL part used in luminance. You shouldn’t have to use it but
it could be interesting if you spot a bug someday. Anyway, you can enable it with the flag
Uniform Block / Uniform Buffer Objects
The UBO system was buggy and was fixed. You might experience issue with them though. I spotted a bug and reported it – you can find the bug report here. That bug is not Haskell related and is related to the i915 Intel driver.
The minor changes were the most important part of luminance-0.7. luminance now officially supports
OpenGL 3.2! When installing luminance, you default to the
gl32 backend. You can select the
backend you want with flags –
gl45-bindless-textures – but keep in mind you need the
appropriate hardware to be able to use it. Because you need to use flags, you won’t be able to
switch to the backend you want at runtime – that’s not the purpose of such a change though.
The performance gap should be minor between
gl45 but still. Basically, OpenGL 4.5 adds
the support for DSA, which is very handy and less
ill-designed that previous iterations of OpenGL. So a lot of code had to be rewritten to implement
luminance’s stateless interface without breaking performance nor bring them down.
I might add support for other backends later on – like an OpenGL ES backend and WebGL one – but that won’t ship that soon though because I have a ton of work to do, and yet need to provide you with a concrete, beautiful, fast, appealing and eye-blowing demo with luminance! ;)
Feel free to test the
gl32 backend and give me back feedback!
However, if I spent so much time on that 0.7 version, it’s because I had issue whilst writing the
gl32 backend. Indeed, I spotted several bugs on my Intel HD card. This is my OpenGL version string
for my Intel IGP card:
OpenGL core profile version string: 3.3 (Core Profile) Mesa 11.0.4
The architecture is Haswell. And on such a card (
i915 linux driver) I’ve found two bugs while
gl32 backend with luminance-samples-0.7.
For unknown reason, the
Texture sample failed on my Intel IGP but ran smoothly and flawlessly on
my nVidia GPU. I spent a lot of time trying to figure out what I was missing, but eventually changed
the sampler type – it’s now a
sampler2D – and… it worked. I reported the issue to the intel dev
team. So if you hit that error too, please leave a message here so that I can have more hindsight
about that error and see what I can do.
Uniform block and
This is a very nasty issue that kept me awoken for days trying to fix my code while it was a driver bug. It’s a big technical, so I’ll just leave a link to the bug tracker so that you can read it if you want to.
Ok, let’s talk.
When creating a new shader stage, you now have to use the function
createStage – instead of
several functions like
createVertexShader. That change is important so that I can add new shader
types without changing the interface, and because some shader can fail to be created. For instance,
gl32 backend, trying to build a tessellation shader will raise an error.
When a shader stage creation fails, the
UnsupportedStage error is raised and holds the type of the
stage that failed.
Finally, the interface for the cubemaps changed a bit – you don’t have access to width and height anymore, that was error-prone and useless; you’re stick to a size parameter.
I’d like to thank all people supporting me and luminance. I’ll be watching reactions to that major and important release as it will cover more people with cheaper and well-spread GPUs.
Happy hacking! :)