It’s been a few days I haven’t talked about luminance. I’ve been working on it a lot those days along with wavefront. In order that you keep up to date, I’ll describe the changes I made in those packages you have a talk about the future directions of those packages.
I’ll also give a snippet you can use to load geometries with
wavefront and adapt them to embed into luminance so that you can
actually render them! A package might come up from that kind of
snippet – luminance-wavefront? We’ll see that!
This package has received several changes among two major
increments and several fixes. In the first place, I removed some
code from the interface that was useless and used only for test
purposes. I removed the Ctxt object – it’s a type
used by the internal lexer anyways, so you don’t have to know
about it – and exposed a type called WavefrontOBJ.
That type reprents the parsed Wavefront data and is the
main type used by the library in the interface.
Then, I also removed most of the modules, because they’re re-exported by the main module – Codec.Wavefront. I think the documentation is pretty straight-forward, but you think something is missing, please shoot a PM or an email! ;)
On the bugs level, I fixed a few things. Among them, there was a nasty bug in the implementation of an internal recursive parser that caused the last wavefront statement to be silently ignored.
I’d also like to point out that I performed some benchmarks – I will provide the data later on with a heap profile and graphs – and I’m pretty astonished with the results! The parser/lexer is insanely fast! It only takes a few milliseconds (between 7ms and 8ms) to load 50k faces (a 2MB .obj file). The code is not yet optimized, so I guess the package could go even faster!
You can find the changelog here.
I made a lot of work on luminance lately. First, the
V type – used to represent vertex components
– is not anymore defined by luminance but by linear. You
can find the type here.
You’ll need the DataKinds extension to write types
like V 3 Float.
That change is due to the fact linear is a mature library with
a lot of interesting functions and types everyone might use when
doing graphics. Its V
type has several interesting instances – Storable,
Ord, etc. – that are required in luminance. Because
it’s not simple to build such V, luminance provides
you with three functions to build the 1D, 2D and 3D versions – vec2,
vec3
and vec4.
Currently, that type is the only one you can use to build
vertex components. I might add V2,
V3 and V4 as well later.
An interesting change: the Uniform typeclass has
a lot of new instances! Basically, all vector
types from linear, their array version and the 4x4 floating matrix
– M44 Float. You can find the list of all instances
here.
A new function was added to the Graphics.Lumimance.Geometry
module called nubDirect.
That function performs in linear logarithmic time and is used to
turn a direct representation of vertices into a pair of
data used to represent indexed vertices. The new list of
vertices stores only unique vertices and the list of integral
values stores the indices. You can then use both the information
to build indexed geometries – see createGeometry
for further details.
The interface to transfer texels to textures has changed. It
doesn’t depend on Foldable anymore but on
Data.Vector.Storable.Vector. That change is due to
the fact that the Foldable solution uses
toList behind the hood, which causes bad performance
for the simple reason that we send the list to the GPU through the
FFI. It’s then more efficient to use a Storable
version. Furthermore, th most known package for textures loading –
JuicyPixels
– already uses that type of Vector. So you just have
to enjoy the new performance boost! ;)
About bugs… I fixed a few ones. First, the implementation of
the Storable instance for (:.)
had an error for sizeOf. The implementation must be
lazy in its argument, and the old one was not, causing
undefined crashes when using that type. The
strictness was removed and now everything works just fine!
Two bugs that were also fixed: the indexed render and the render of geometries with several vertex components. Those bugs were easy to fix and now you won’t experience those issues anymore.
I thought it would be a hard task but I’m pretty proud of how
easy it was to interface both the packages! The idea was to
provide a function that would turn a WavefrontOBJ
into a direct representation of luminance vertices.
Here’s the function that implements such a conversion:
type Vtx = V 3 Float :. V 3 Float -- location :. normal
objToDirect :: WavefrontOBJ -> Maybe [Vtx]
objToDirect obj = traverse faceToVtx (toList faces)
where
locations = objLocations obj
normals = objNormals obj
faces = objFaces obj
faceToVtx face = do
let face' = elValue face
vni <- faceNorIndex face'
v <- locations !? (faceLocIndex face' - 1)
vn <- normals !? (vni - 1)
let loc = vec3 (locX v) (locY v) (locZ v)
nor = vec3 (norX vn) (norY vn) (norZ vn)
pure (loc :. nor)As you can see, that function is pure and will eventually turn
a WavefrontOBJ into a list of Vtx.
Vtx is our own vertex type, encoding the location and
the normal of the vertex. You can add texture coordinates if you
want to. The function fails if a face’s index has no normal
associated with or if an index is out-of-bound.
And… and that’s all! You can already have your
Geometry with that – direct one:
x <- fmap (fmap objToDirect) (fromFile "./ubercool-mesh.obj")
case x of
Right (Just vertices) -> createGeometry vertices Nothing Triangle
_ -> throwError {- whatever you need as error there -}You want an indexed version? Well, you already have everything to do that:
x <- fmap (fmap (nubDirect . objToDirect) (fromFile "./ubercool-mesh.obj")
case x of
Right (Just (vertices,indices)) -> createGeometry vertices (Just indices) Triangle
_ -> throwError {- whatever you need as error there -}Even though the nubDirect performs in a pretty
good complexity, it takes time. Don’t be surprised to see the
“loading” time longer then.
I might package those snippets and helpers around them into a
luminance-wavefront package, but that’s not trivial
as the vertex format should be free.
I received a lot of warm feedback from people about what I do in the Haskell community, and I’m just amazed. I’d like to thank each and everyone of you for your support – I even got support from non-Haskellers!
What’s next then… Well, I need to add a few more textures to
luminance – texture arrays are not supported yet, and the
framebuffers have to be altered to support all kind of textures. I
will also try to write a cheddar interpreter
directly into luminance to dump the String type of
shader stages and replace it with cheddar’s whatever will be. For
the long terms, I’ll add UBO and SSBO to luminance, and…
compatibility with older OpenGL versions.
Once again, thank you, and keep the vibe!