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FieldTrip

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[[Category:Libraries]]
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[[Category:Graphics]]
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[[Category:3D]]
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[[Category:Packages]]
   
Field Trip is a library for describing 3D scenes declaratively. It is intended
+
== Abstract ==
as an open and machine/technology independent API for building animations as well as still life pictures. We also supply a bridge to use the OpenGL rendering engine, but other technologies are envisioned, for example a raytracing based renderer.
 
   
It is in active development by Conal Elliot and Andy Gill.
+
[[Image:Torus-pair-d-shadowed.png|right|thumb|300px|Torus pair modeled and rendered in FieldTrip]]
  +
'''FieldTrip''' is a library for functional 3D graphics, intended for building static, animated, and interactive 3D geometry, efficient
  +
enough for real-time synthesis and display.
  +
Our first renderer uses OpenGL, with the usual visual limitations.
  +
Since FieldTrip is functional, it is about ''being'' rather than ''doing''.
  +
One describes what models are, not how to render them.
   
== Architecture ==
+
FieldTrip is work-in-progress.
  +
It's being released to show what's going on and see who's interested in collaborating on developing it further.
   
The basic purpose of the core FieldTrip library is to allow a user build a 3D scene. The principal types are as follows.
+
Besides this wiki page, here are more ways to find out about and get involved with FieldTrip:
  +
* Join the [http://www.haskell.org/mailman/listinfo/FieldTrip FieldTrip mailing list].
  +
* Visit the [http://hackage.haskell.org/cgi-bin/hackage-scripts/package/FieldTrip Hackage page] for library documentation and to download & install.
  +
* Or install with <tt>cabal install FieldTrip</tt>. See [[#Installation dependencies|Installation dependencies]] below.
  +
* Get the code repository: <tt>darcs get http://code.haskell.org/FieldTrip</tt>
  +
<!-- * See the [[FieldTrip/Versions| version history]]. -->
  +
* Report bugs and request features on [http://trac.haskell.org/FieldTrip/ the tracker].
   
<dl>
+
== Basic types ==
<dt><b>data</b> Geometry3</dt>
 
<dd>A abstract type describing a number of objects in 3D space. These objects can be scaled, rotated or translated in space, as well as grouped.
 
</dd>
 
   
<dt><b>type</b> Surf a = (a,a) -> (a,a,a)</dt>
+
The basic purpose of the core FieldTrip library is to allow a user build 3D geometry, from individual simple shapes to full 3D scenes.
<dd>
+
The principal types are as follows.
Primitive Geometry3's are build from surfaces, which represented as a function from R2 to R3 - so this function maps every point on the (2D) surface onto a point in 3D.
 
</dd>
 
   
<dt>Normal and Derivatives</dt>
+
; <hask>Geometry3</hask>
<dd>One novel feature of FieldTrip is the automation of derivative computation. We represent our surfaces using (more text) .. This design allows us to perform functions over surfaces, adding ripples and other deformities.
+
: 3D geometry. These values can be spatially transformed in space (affinely: scale, rotate, translate) and combined (union).
   
</dd>
+
; <hask>Surf a = (a,a) -> (a,a,a)</hask>
  +
: Parametric surfaces, i.e., mappings from 2D to 3D. Normals are constructed automatically and exactly via derivatives, thanks to the [[vector-space]] library. These normals are used for shading. For simplicity and composability, ''surfaces are curved'', not faceted.
  +
: Surface ''rendering'' tessellates adaptively, caching tessellations in an efficient, infinite data structure for reuse. The mechanism for choosing tessellation is a very primitive placeholder. FieldTrip provides some basic shapes of surfaces (spheres, torus, cubes, etc) and many functions for manipulating surfaces, colors, etc.
   
<dt><b>type</b> ImageC = (a,a) -> Color</dt>
+
; <hask>Geometry2</hask>
<dd>We represent all 2D images as straightforward functions from location (in 2D) to color (including an alpha component). We use [http://en.wikipedia.org/wiki/Bilinear_interpolation bilinear interpolation] to sample imported image data. Fonts are also supported via our ImageC idiom.
+
: 2D geometry. There's a function (<hask>flatG</hask>) to embed 2D into 3D.
<dd>
 
   
</dl>
+
; <hask>Image o = (R,R) -> o</hask>
  +
: A primitive placeholder for functional imagery in the spirit of [http://conal.net/Pan Pan]. The intention is to use this type or
  +
something like it for texture mapping. Much design and implementation work to be done.
   
The standard way of creating basic Geometry3 uses all these architectural features, using Surf and ImageC to realize a Geometry3, as well as the derivative mechanism to compute normals for realistic lighting.
+
== Example ==
   
In FieldTrip we provide some basic shapes of surfaces (spheres, torus, cubes, etc) and many functions for manipulating surfaces, colors, etc.
+
The code for the static torus pair shown above:
  +
<haskell>
  +
torusPair :: Geometry3
  +
torusPair = f red (1/2) `mappend` pivot3X (f green (-1/2))
  +
where
  +
tor = torus 1 (2/5)
  +
f :: Col -> R -> Geometry3
  +
f col dx = materialG (plastic col) (move3X dx tor)
  +
</haskell>
  +
where <hask>pivot3X</hask> and <hask>move3X</hask> are simple helper short-hands for 3D transformation.
   
We combine a Geometry3 with lights, fog, and other effects, as well as a camera location, and give this combination (the details are still in flux) to the renderer.
+
The <code>[http://hackage.haskell.org/packages/archive/FieldTrip/0.2.2/doc/html/Graphics-FieldTrip-Geometry3.html#v%3Atorus torus]</code> function used here is a
  +
simple wrapper around a parametric surface defined as follows:
  +
<haskell>
  +
-- | Torus, given radius of sweep circle and cross section
  +
torus :: (Floating s, VectorSpace s, Scalar s ~ s) => s -> s -> Surf s
  +
torus sr cr = revolve (const (sr,0) ^+^ cr *^ circle)
  +
</haskell>
  +
where <hask>revolve</hask> and <hask>circle</hask> are defined in
  +
[http://hackage.haskell.org/packages/archive/FieldTrip/latest/doc/html/Graphics-FieldTrip-ParamSurf.html Graphics.FieldTrip.ParamSurf], along with other tools for shape generation.
   
  +
The trick to turning this polymorphic <hask>torus</hask> function into a <hask>Geometry3</hask> is to use a derivative tower (from
  +
[[vector-space]]) for the type parameter <hask>s</hask>.
  +
<haskell>
  +
surfG :: Surf (Vector2 R :> R) -> Geometry3
   
  +
torus :: R -> R -> Geometry3
  +
torus sr cr = surfG (P.torus (pureD sr) (pureD cr))
  +
</haskell>
   
== FieldTrip for Animation using OpenGL ==
+
''[fill in more examples]''
   
Our first renderer uses OpenGL.
+
== FieldTrip meets Reactive ==
FieldTrip is intended to be efficient enough for real time image generation.
 
We do not draw shadows or reflections when rendering, and inherit the OpenGL anti-aliasing policy.
 
   
Towards efficiency we have a dynamic accuracy graphics context internally, which uses less triangles when [http://en.wikipedia.org/wiki/Tessellation tessellating] a surface when performance is needed. When finished this will allow us to automatically use less triangle for distance objects, for example.
+
FieldTrip contains no support for animation, because we intend it to be used with the [[Reactive]] functional reactive programming
  +
([[FRP]]) library (and possibly other animation frameworks).
  +
By design, FieldTrip is completely orthogonal to any formulation or implementation of FRP.
   
We want our library to be usable in real time by FRP-based code, though FRP is by design completely orthogonal to FieldTrip.
+
The [[reactive-fieldtrip]] project connects [[Reactive]] and FieldTrip.
   
== The FieldTrip Universe ==
+
The picture above comes from an animation in [[reactive-fieldtrip]].
  +
Load <code>src/Test.hs</code>, as follows:
  +
<pre>
  +
~/Haskell$ cd reactive-fieldtrip/src
  +
~/Haskell/reactive-fieldtrip/src$ ghci
  +
GHCi, version 6.10.1: http://www.haskell.org/ghc/ :? for help
  +
Loading package ghc-prim ... linking ... done.
  +
Loading package integer ... linking ... done.
  +
Loading package base ... linking ... done.
  +
Prelude> :l Test
  +
:l Test
  +
[1 of 2] Compiling FRP.Reactive.FieldTrip.Adapter ( FRP/Reactive/FieldTrip/Adapter.hs, interpreted )
  +
[2 of 2] Compiling Test ( Test.hs, interpreted )
  +
Ok, modules loaded: FRP.Reactive.FieldTrip.Adapter, Test.
  +
</pre>
  +
Then run the example:
  +
<pre>
  +
*Test> anim3 (const (spinningG torusPair))
  +
Loading package OpenGL-2.2.1.1 ... linking ... done.
  +
Loading package syb ... linking ... done.
  +
Loading package base-3.0.3.0 ... linking ... done.
  +
[...]
  +
Loading package reactive-0.9.0 ... linking ... done.
  +
Loading package FieldTrip-0.2.2 ... linking ... done.
  +
Loading package reactive-glut-0.0.5 ... linking ... done.
  +
</pre>
   
Field trip has a number of packages.
+
== Some videos ==
   
<dl>
+
* [http://www.youtube.com/watch?v=ulPsJzUCQi8 Texture-mapped Earth.]
<dt>FieldTrip</td>
+
* [http://www.youtube.com/watch?v=WNB5V9Z7Obc The torus demo running in GHCi.]
<dd>The basic library of combinators for building 3D scenes.
 
</dd>
 
   
<dt>FieldTrip-OpenGL</td>
+
== Problems and solutions ==
<dd>The library for rendering a scene in real time, using the OpenGL library.
 
</dd>
 
   
<dt>FieldTrip-GLUT</td>
+
=== Installation dependencies ===
<dd>The library for opening a viewer into a FieldTrip OpenGL based scene.
 
</dd>
 
   
<dt>FieldTrip-GLFW</td>
+
==== Haskell packages ====
<dd> Same, for GLFW.
 
</dd>
 
   
<dt>FieldTrip-OSX</td>
+
You'll need the OpenGL and GLUT packages. If you are using synaptics/apt-get, those are called libghc6-opengl-dev and libghc6-glut-dev. If you're using cabal-install, it will take care of the dependencies for you (see "Non-Haskell libraries" below though).
<dd>An alternative version of GLUT/GLFW that provides access the the OSX extensions, for example .mov file capture.
 
</dd>
 
</dl>
 
   
There will be more!
+
==== Non-Haskell libraries ====
  +
  +
Make sure that you have the opengl-dev and glut-dev libraries installed. If you don't have them, there are two ways to fail: Either on the installation of the corresponding Haskell libraries, like this:
  +
  +
<pre>
  +
configure: error: no GLUT header found, so this package cannot be built
  +
See `config.log' for more details.
  +
cabal: Error: some packages failed to install:
  +
GLUT-2.1.1.2 failed during the configure step. The exception was:
  +
exit: ExitFailure 1
  +
</pre>
  +
  +
Or, if you do have the Haskell packages and C libraries, but accidentally removed the opengl-dev and glut-dev libraries, you can end up with FieldTrip just producing black windows.
  +
  +
===== Linking problems on Debian Lenny =====
  +
  +
You may experience linker problems on Debian Lenny. Running:
  +
  +
> ghc --make -main-is Test Test.hs
  +
  +
can give you:
  +
  +
<pre>
  +
Linking Test ...
  +
/home/ghc/.cabal/lib/reactive-glut-0.1.6/ghc-6.10.1/libHSreactive-glut-0.1.6.a(SimpleGL.o): In function `s5SW_info':
  +
(.text+0x1654): undefined reference to `glutInitDisplayMode'
  +
/home/ghc/.cabal/lib/reactive-glut-0.1.6/ghc-6.10.1/libHSreactive-glut-0.1.6.a(SimpleGL.o): In function `s5SW_info':
  +
(.text+0x1668): undefined reference to `glutInitWindowSize'
  +
...
  +
</pre>
  +
  +
This is a HOpenGL problem and has already been [http://www.haskell.org/pipermail/haskell-cafe/2008-September/047357.html reported here] and a [http://www.haskell.org/pipermail/haskell-cafe/2008-September/047815.html solution here]. To make a long story short, you need to explicitly link with glut when compiling:
  +
  +
> ghc --make -lglut -main-is Test Test.hs

Latest revision as of 19:45, 3 July 2009


Contents

[edit] 1 Abstract

(thumbnail)
Torus pair modeled and rendered in FieldTrip

FieldTrip is a library for functional 3D graphics, intended for building static, animated, and interactive 3D geometry, efficient enough for real-time synthesis and display. Our first renderer uses OpenGL, with the usual visual limitations. Since FieldTrip is functional, it is about being rather than doing. One describes what models are, not how to render them.

FieldTrip is work-in-progress. It's being released to show what's going on and see who's interested in collaborating on developing it further.

Besides this wiki page, here are more ways to find out about and get involved with FieldTrip:

[edit] 2 Basic types

The basic purpose of the core FieldTrip library is to allow a user build 3D geometry, from individual simple shapes to full 3D scenes. The principal types are as follows.

Geometry3
3D geometry. These values can be spatially transformed in space (affinely: scale, rotate, translate) and combined (union).
Surf a = (a,a) -> (a,a,a)
Parametric surfaces, i.e., mappings from 2D to 3D. Normals are constructed automatically and exactly via derivatives, thanks to the vector-space library. These normals are used for shading. For simplicity and composability, surfaces are curved, not faceted.
Surface rendering tessellates adaptively, caching tessellations in an efficient, infinite data structure for reuse. The mechanism for choosing tessellation is a very primitive placeholder. FieldTrip provides some basic shapes of surfaces (spheres, torus, cubes, etc) and many functions for manipulating surfaces, colors, etc.
Geometry2
2D geometry. There's a function (
flatG
) to embed 2D into 3D.
Image o = (R,R) -> o
A primitive placeholder for functional imagery in the spirit of Pan. The intention is to use this type or

something like it for texture mapping. Much design and implementation work to be done.

[edit] 3 Example

The code for the static torus pair shown above:

torusPair :: Geometry3
torusPair = f red (1/2) `mappend` pivot3X (f green (-1/2))
 where
   tor = torus 1 (2/5)
   f :: Col -> R -> Geometry3
   f col dx = materialG (plastic col) (move3X dx tor)
where
pivot3X
and
move3X
are simple helper short-hands for 3D transformation.

The torus function used here is a simple wrapper around a parametric surface defined as follows:

-- | Torus, given radius of sweep circle and cross section
torus :: (Floating s, VectorSpace s, Scalar s ~ s) => s -> s -> Surf s
torus sr cr = revolve (const (sr,0) ^+^ cr *^ circle)
where
revolve
and
circle
are defined in

Graphics.FieldTrip.ParamSurf, along with other tools for shape generation.

The trick to turning this polymorphic
torus
function into a
Geometry3
is to use a derivative tower (from vector-space) for the type parameter
s
.
surfG :: Surf (Vector2 R :> R) -> Geometry3
 
torus :: R -> R -> Geometry3
torus sr cr = surfG (P.torus (pureD sr) (pureD cr))

[fill in more examples]

[edit] 4 FieldTrip meets Reactive

FieldTrip contains no support for animation, because we intend it to be used with the Reactive functional reactive programming (FRP) library (and possibly other animation frameworks). By design, FieldTrip is completely orthogonal to any formulation or implementation of FRP.

The reactive-fieldtrip project connects Reactive and FieldTrip.

The picture above comes from an animation in reactive-fieldtrip. Load src/Test.hs, as follows:

    ~/Haskell$ cd reactive-fieldtrip/src
    ~/Haskell/reactive-fieldtrip/src$ ghci
    GHCi, version 6.10.1: http://www.haskell.org/ghc/  :? for help
    Loading package ghc-prim ... linking ... done.
    Loading package integer ... linking ... done.
    Loading package base ... linking ... done.
    Prelude> :l Test
    :l Test
    [1 of 2] Compiling FRP.Reactive.FieldTrip.Adapter ( FRP/Reactive/FieldTrip/Adapter.hs, interpreted )
    [2 of 2] Compiling Test             ( Test.hs, interpreted )
    Ok, modules loaded: FRP.Reactive.FieldTrip.Adapter, Test.

Then run the example:

    *Test> anim3 (const (spinningG torusPair))
    Loading package OpenGL-2.2.1.1 ... linking ... done.
    Loading package syb ... linking ... done.
    Loading package base-3.0.3.0 ... linking ... done.
    [...]
    Loading package reactive-0.9.0 ... linking ... done.
    Loading package FieldTrip-0.2.2 ... linking ... done.
    Loading package reactive-glut-0.0.5 ... linking ... done.

[edit] 5 Some videos

[edit] 6 Problems and solutions

[edit] 6.1 Installation dependencies

[edit] 6.1.1 Haskell packages

You'll need the OpenGL and GLUT packages. If you are using synaptics/apt-get, those are called libghc6-opengl-dev and libghc6-glut-dev. If you're using cabal-install, it will take care of the dependencies for you (see "Non-Haskell libraries" below though).

[edit] 6.1.2 Non-Haskell libraries

Make sure that you have the opengl-dev and glut-dev libraries installed. If you don't have them, there are two ways to fail: Either on the installation of the corresponding Haskell libraries, like this:

    configure: error: no GLUT header found, so this package cannot be built                                                      
    See `config.log' for more details.                                                                                           
    cabal: Error: some packages failed to install:                                                                               
    GLUT-2.1.1.2 failed during the configure step. The exception was:                                                            
    exit: ExitFailure 1

Or, if you do have the Haskell packages and C libraries, but accidentally removed the opengl-dev and glut-dev libraries, you can end up with FieldTrip just producing black windows.

[edit] 6.1.2.1 Linking problems on Debian Lenny

You may experience linker problems on Debian Lenny. Running:

> ghc --make -main-is Test Test.hs

can give you:

 Linking Test ...
 /home/ghc/.cabal/lib/reactive-glut-0.1.6/ghc-6.10.1/libHSreactive-glut-0.1.6.a(SimpleGL.o): In function `s5SW_info':
 (.text+0x1654): undefined reference to `glutInitDisplayMode'
 /home/ghc/.cabal/lib/reactive-glut-0.1.6/ghc-6.10.1/libHSreactive-glut-0.1.6.a(SimpleGL.o): In function `s5SW_info':
 (.text+0x1668): undefined reference to `glutInitWindowSize'
 ...

This is a HOpenGL problem and has already been reported here and a solution here. To make a long story short, you need to explicitly link with glut when compiling:

> ghc --make -lglut -main-is Test Test.hs