# FieldTrip

### From HaskellWiki

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m (→FieldTrip meets Reactive: making the torus animation) |
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The [[reactive-fieldtrip]] project connects [[Reactive]] and FieldTrip. |
The [[reactive-fieldtrip]] project connects [[Reactive]] and FieldTrip. |
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+ | To picture above comes from an animation in [[reactive-fieldtrip]]. |
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+ | Load src/Test.hs into ghci, and type |
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+ | <haskell> |
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+ | anim3 (spinningG torusPair) |
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+ | </haskell> |
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+ | |||

+ | The code for the static torus pair: |
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+ | <haskell> |
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+ | torusPair :: Geometry3 |
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+ | torusPair = f red (1/2) `mappend` pivot3X (f green (-1/2)) |
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+ | where |
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+ | tor = torus 1 (2/5) |
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+ | f :: Col -> R -> Geometry3 |
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+ | f col dx = plasmat col (move3X dx tor) |
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+ | </haskell> |
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+ | where <hask>pivot3X</hask> and <hask>move3X</hask> are simple helper functions for 3D transformation, and <hask>plasmat</hask> applies a color with a plastic look (defined in <code>Test.hs</code>. |

## Revision as of 19:51, 10 November 2008

## 1 Abstract

**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.

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

- Join the FieldTrip mailing list.
- Peruse the library documentation.
- Install from Hackage.
- Download the code repository:
. Patches welcome.`darcs get http://code.haskell.org/FieldTrip` - Report bugs and request features on the tracker.
- Examine the version history.

## 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 () to embed 2D into 3D.flatG

- 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.

## 3 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. To picture above comes from an animation in reactive-fieldtrip. Load src/Test.hs into ghci, and type

anim3 (spinningG torusPair)

The code for the static torus pair:

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 = plasmat col (move3X dx tor)

`Test.hs`

.