GridFlow 0.5.0 - reference index
Conventions of this Manual
Grid Protocol
Picture Protocol
Conventions of this Manual
Grid Protocol
This section is useful if you want to do more than just pictures with GridFlow.
each element of a grid is an integer. the range of allowed integer values is called signed 32-bit and is -2147483648 to 2147483647 (which is -231 to 231-1).
a single-dimensional grid of 3 elements (a triplet) is called dim(3). a three-dimensional grid of 240 rows of 320 columns of triplets is called dim(240,320,3).
There is a sequence in which elements of a Grid are stored and transmitted. Dimension 0 is called "outer" or "first" and dimension N-1 is called "inner" or "last". They are called so because if you select a position in the first dimension of a grid, the selected part is of the same shape minus the first dimension; so in dim(240,320,3) if you select row 51 (or whichever valid row number), you get a dim(320,3). if you select a subpart two more times you get to a single number.
At each such level, elements are sent/stored in their numeric order, and are numbered using natural numbers starting at 0. This ordering usually does not matter, but sometimes it does. Most notably, @import, @export and @redim care about it.
On the other hand, order of dimensions usually does matter; this is what distinguishes rows from columns and channels, for example. Most objects care about the distinction.
A grid with only 1 element in a given dimension is different from one lacking that dimension; it won't have the same meaning. You can use this property to your advantage sometimes.
Zero-dimensional grids exist. They are called dim(). They can only contain a single number.
Picture Protocol
This section is useful if you want to know what a picture is in terms of a grid.
A picture is a three-dimensional Grid:
- 0 : rows
- 1 : columns
- 2 : channels
Channels for the RGB color model are:
- 0 : red
- 1 : green
- 2 : blue
Because Grids are made of 32-bit integers, a three-channel picture uses 96 bpp (bits per pixel), and have to be downscaled to 24 bpp (or 16 bpp) for display. That huge amount of slack is there because when you create your own effects you often have intermediate results that need to be of higher precision than a normal picture. Especially, results of multiplications are big and should not overflow before you divide them back to normal; and similarly, you can have negative values all over, as long as you take care of them before they get to the display.
In the final conversion, high bits are just ignored. This means: black is 0, maximum is 255, and values wrap like with % 256. If you want to clip them, you may use "@ max 0" and "@ min 255" objects.
GridFlow 0.5.0 Documentation
by Mathieu Bouchard matju@sympatico.ca
and
Alexandre Castonguay acastonguay@artengine.ca