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Basic types for computer graphics.
Gg defines types and functions for floats, vectors, points, matrices, quaternions, sizes, axis aligned boxes, colors, color profiles, linear bigarrays and raster data.
Consult the basics.
Open the module to use it, this defines only modules and types in your scope.
module Float : sig ... end
Floating point number utilities.
An n-dimensional vector
v is a sequence of n, zero indexed, floating point components. We write
vi the ith component of a vector.
The matrix types are defined here so that they can be used in vector modules; their modules are here.
module type V = sig ... end
Implemented by all vector types.
module V2 : sig ... end
module V3 : sig ... end
module V4 : sig ... end
An n-dimensional point
p is a vector of the corresponding dimension. The components of the vector are the point's coordinates.
type p2 = v2
The type for 2D points.
type p3 = v3
The type for 3D points.
module type P = sig ... end
Implemented by all point types.
module P2 : sig ... end
module P3 : sig ... end
Unit quaternions represent rotations in 3D space. They allow to smoothly interpolate between orientations. A quaternion is a 4D vector, whose components
w represents the quaternion
type quat = v4
The type for quaternions.
module Quat : sig ... end
An mxn matrix
a is an array of m rows and n columns of floating point elements. We write
aij the element of
a located at the ith row and jth column.
Matrix constructors specify matrix elements in row-major order so that matrix definitions look mathematically natural with proper code indentation. However elements are stored and iterated over in column-major order.
module type M = sig ... end
Implemented by all (square) matrix types.
module M2 : sig ... end
2D square matrices.
module M3 : sig ... end
3D square matrices.
module M4 : sig ... end
4D square matrices.
An n-dimensional size
s represents extents in n-dimensional space.
type size2 = v2
The type for sizes in 2D space.
type size3 = v3
The type for sizes in 3D space.
module type Size = sig ... end
Implemented by all size types.
module Size1 : sig ... end
Sizes in 1D space.
module Size2 : sig ... end
Sizes in 2D space.
module Size3 : sig ... end
Sizes in 3D spaces.
An n-dimensional axis-aligned box
b is defined by an n-dimensional point
o, its origin, and an n-dimensional size
s. Operations on boxes with negative sizes are undefined.
The space S(
b) spanned by
b is [
s0] x ... x [
sn-1]. The extremum points of this space are the box's corners. There is a distinguished n-dimensional
empty box such that S(
empty) is empty.
The type for 1D axis-aligned boxes (closed intervals).
The type for 2D axis-aligned boxes (rectangles).
The type for 3D axis-aligned boxes (cuboids).
module type Box = sig ... end
Implemented by all axis-aligned box types.
module Box1 : sig ... end
1D axis-aligned boxes.
module Box2 : sig ... end
2D axis-aligned boxes.
module Box3 : sig ... end
3D axis-aligned boxes.
module Color : sig ... end
Colors and color profiles.
Linear bigarrays and bigarray buffers
type ('a, 'b) bigarray = ('a, 'b, Bigarray.c_layout) Bigarray.Array1.t
The type for linear bigarrays.
type buffer = [
`Int8 of (int, Bigarray.int8_signed_elt) bigarray
`Int16 of (int, Bigarray.int16_signed_elt) bigarray
`Int32 of (int32, Bigarray.int32_elt) bigarray
`Int64 of (int64, Bigarray.int64_elt) bigarray
`UInt8 of (int, Bigarray.int8_unsigned_elt) bigarray
`UInt16 of (int, Bigarray.int16_unsigned_elt) bigarray
`UInt32 of (int32, Bigarray.int32_elt) bigarray
`UInt64 of (int64, Bigarray.int64_elt) bigarray
`Float16 of (int, Bigarray.int16_unsigned_elt) bigarray
`Float32 of (float, Bigarray.float32_elt) bigarray
`Float64 of (float, Bigarray.float64_elt) bigarray
The type for linear bigarray buffers.
module Ba : sig ... end
Linear bigarrays and bigarray buffers.
module Raster : sig ... end
Gg is designed to be opened in your module. This defines only types and modules in your scope, no values. Thus to use
Gg start with :
In the toplevel enter:
> #require "gg.top";;
to automatically open
Gg and install printers for the types.
Most types and their functions are defined with the following conventions. The type is first defined in
v2 for 2D vectors, a module for it follows. The name of the module is the type name capitalized, e.g.
V2 for 2D vectors and it has the following definitions:
- a type
tequal to the original toplevel type (
intvalue that indicates the dimensionality of the type (
v, a constructor for the type (
ppto convert values to a textual representation for debugging purposes and toplevel interaction
comparethe standard functions that make a module a good functor argument (
compare_fwhich compare like
comparebut allow to use a client provided function to compare floats (
trto apply linear and affine transforms on the type (
- Other accessors (e.g.
V2.x), constants (e.g.
V2.zero), functions (e.g.
V2.dot) and predicates (e.g.
V2.exists) specific to the type.
- Modules that represent the same object but for different dimensions, like
V4for vectors, usually share a common signature. This common signature is collected in a module type defined in
Gg, this signature is
Some types are defined as simple abreviations. For example the type
p2 for 2D points is equal to
v2. These types also have a module whose name is the type name capitalized,
P2 in our example. However this module only provides alternate constructors, constants and accessors and the extended functionality specific to the type. You should fallback on the module of the abreviated type (
V2 in our example) for other operations. The aim of these types is to make your code and signatures semantically clearer without the burden of explicit conversions.
Finally there are some types and modules like
Color whose structure is different because they provide specific functionality.
Here are a few other conventions :
- Numbers in names indicate dimensionality. For example
M4.scale3indicates scale in 3D space while
M4.scale4scale in 4D space.
- Most functions take the value they act upon first. But exceptions abound, to match OCaml conventions, to have your curry or to match mathematical notation (e.g.
- Conversion functions follow the
of_conventions. Thus to convert a value of type
t'to a value of type
tlook for the function named
To conclude note that it is sometimes hard to find the right place for a function. If you cannot find a function look into each of the modules of the types you want to act upon.
- In 3D space we assume a right-handed coordinate system.
- Angles are always given in radians (except in this function...).
- In 2D space positive angles determine counter clockwise rotations.
- In 3D space positive angles determine rotations directed according to the right hand rule.
Note on colors
Values of type
color are in a linear sRGB space as this is the space to work in if you want to process colors correctly (e.g. for blending). The constructor
Color.v_srgb takes its parameters from a non-linear sRGB space and converts them to linear sRGB.
# let c = Color.v_srgb 0.5 0.5 0.5 1.0;; - : Gg.color = (0.214041 0.214041 0.214041 1)
This is the constructor you are likely to use when you specify color constants (e.g. to specify a color value matching a CSS color). If you need an sRGB color back from a
color value use
# Color.to_srgba c;; - : Gg.Color.srgba = (0.5 0.5 0.5 1)
Remarks and Tips
- Everything is tail-recursive.
- Do not rely on the output of printer functions, they are subject to change. The only exception is the function
Float.ppthat output a lossless textual representation of floats. While the actual format is subject to change it will remain compatible with
- All modules can be directly given as arguments to
Map.Make. However this will use
Stdlib.compareand thus binary comparison between floats. Depending on the intended use this may be sensible or not. Comparisons with alternate functions to compare floats can be defined by using the functions named
V2.compare_f). An alternate float comparison function is
Float.compare_tolthat combines relative and absolute float comparison in a single test, see
Float.equal_tolfor the details.
- For performance reasons some functions of the
Floatmodule are undefined on certain arguments but do not raise
Invalid_argumenton those. As usual do not rely on the behaviour of functions on undefined arguments, these are subject to change.