The Language:

• That it should be readable by a human;
  
• That it should be editable by the computer;
  
• That it should go like the clappers.

Characteristically commands are verbose. It is recommended that typing in commands using longhand is to be avoided and that cut and paste facilities are employed wherever possible.

When loaded, commands are translated into an internal format and the original textfile is discarded. Loaded files may contain command names in any case, truncated names, commands optionally abbreviated with the . character, confused and confusing punctuation and mismatched brackets. When the file is saved, it is cleaned up, reformatted and expanded into a standard format. Unless you know what you are doing, keeping copies of the original files is recommended, as What The Computer Thinks You Are Talking About may initially differ from What You Are Trying To Say.

Error checking is currently implemented mainly at the parsing stage. If the program you feed the computer contains errors, a message will tell you which line they are found on. These messages should be helpful in the process of tracking down mistakes. Runtime error messages are also possible, but should occur rarely in practise.

If your version of this program is unregistered, then you will probably experience difficulties in changing existing textures or getting your own textures to be displayed. Please refer to the Register document for details of why this occurs.

Resources:

There are three one dimensional buffers of &400 16-bit values which may be manipulated. One two dimensional buffer is provided, with dimensions controlled by the size of the sprite to be generated. A buffer for storing colourmaps exists and there is space reserved for the manipulation of &400 variables. These contain unspecified values on entry to the routine.

Texture generation programs are entered when a texture is required. Their execution begins at their first line.

Comments are considered to be anything after a | character. Comments in If...Then...Else lines are treated using the same conventions as in Obey files, i.e. If 1 = 2 THEN |ECHO Equal! ELSE ECHO Not_Equal! would print Not_Equal! in an Obey file, despite the earlier |.

Conventions:

Textures terminate when they reach the End command. It is conventional to place subroutine definitions after the End so they are separate from the main program. The mutator may rely on this in the future.

Everything falls into one of four categories.

These four categories are: Comments, Commands, Functions and Parameters.

Comments are simple: they are considered to be anything after a | character.

Index

Returns (A + B) And &FFFF.

Returns (A - B) And &FFFF.

IF A + B > &FFFF THEN returns &FFFF ELSE returns (A + B).

IF B > A THEN returns 0 ELSE returns (A - B).

IF A + B < &10000 THEN returns (A + B) ELSE returns &20000 - (A + B).

IF A - B > 0 THEN returns (A - B) ELSE returns (B - A).

Returns (A + B) DIV 2.

Returns ((A - B) DIV 2) &FFFF (A and B are considered unsigned).

Returns the greater of A and B (A and B are considered unsigned).

Returns the greater of A and B (A and B are considered unsigned).

Returns A * B And &FFFF.

Returns ((A * B) DIV &10000) And &FFFF.

This produces an effect like a ball bouncing off a ceiling (ahem).

This produces an effect like a ball bouncing off a floor.

Displays the percentage of the texture completed using the hourglass.

The Percentage parameter's domain may be considered as being either from &0 to &63 (99) or from &80 to &63FF (100 * 256 - 1). Using Percentage(&FFFF) turns off the percentage display.

In unregistered versions of the program, textures which do not contain the correct value in their checksum or contain no checksum at all are rejected by the program and not displayed. This limits the extent to which unregistered users may manipulate their textures.

In registered versions, an additional module is supplied which will enable the program (and all future upgrades of it) to read textures independently of the checksum.

A site license or Super-user version will also display whether the checksum is correct, and will write texture files with correct checksums, enabling people other than the author to distribute textures readable by the freeware distributed version of the program.

Digression beginning...

If ... Then ... If ... Then ... Else constructs currently treat the Else as belonging to BOTH Ifs. One can't help thinking that If ... Then ... If ... Then ... Else ... Else should make sense - i.e. the Else should belong to the nearest If. Unless the Ifs are nested in this manner one of them cannot have an Else without the other one getting it too. However, BASIC does not agree (and that's BBC BASIC, the official Englishman's dialect). No doubt the Germans would have implemented it as they are used to recursively peeling verbs from their sentences and correlating them with earlier nouns. Still, the sentence The boy, the girl, the man, kissed, hit, ran is reputed to be good English, though no-one seems quite to be able to get their head 'round it. It is possible to invert the first condition so that the If comes after the Else instead of after the Then (unless the command required there is another If statement).

Obey files don't seem to like their Ifs nested either (programmers must find it easier to just look for the next Else than to count the intermediate Ifs), and so neither does Texture Garden (which tries to follow the Obey file syntax, so its files can be displayed in Obey file syntax-colouring modes in text editors).

...digression end.

As <Condition>s you cannot use <, =, >= != etc.
A list of conditions that are acceptable follows:

IsLessThan(A,B) returns TRUE (&FFFF or -1) if A is less than B, otherwise it returns FALSE (0).

This is useful when creating images by using multiple layers of texture.

Type_R, Type_G and Type_B are the combination-types to be used when adding to an existing sprite for red, green and blue components respectively.

The virtual sprite should not be assumed to be blank when it is created and so the first occurrence of this command should normally use Overwrite,Overwrite,Overwrite as its parameters.

FloydSteinberg dithering may be applied, but will only produce noticable effects if the texture is rendered in 16, 256 or 32K modes. In 16M modes, FloydSteinberg dithering is not required.

The MakeSpriteFromVirtualSprite command usually leaves the virtual sprite unaffected, but if FloydSteinberg dithering is being used, it is altered to the dithered version of the sprite in the selected mode.

One point to note is that dithering should always be set either to Zero or to FloydSteinberg before this command is executed. As the dithering command is affected by the mutator this should not be as a raw number, but as one of the strings mentioned above.

This is for compatibility with other possible future dithering routines.

* Note that with these commands, the sprite may not subsequently be added to. These operations may stop the resulting sprite from tessellating.

# These commands should only be used when resizing the texture using the front-end is not necessary, as they will stop textures from being resized.

What noise is used and how the filtering is performed is affected by the following commands: Seed(Value), Phase(Value), NoiseToBeFiltered(Value), CreateCosineSymmetry, CreateSineSymmetry, CreateCosineArtefacts(Value), CreateSineArtefacts(Value), AbandonCosinePhase, and AbandonSinePhase.

Exactly how these commands affect the filtering of the noise is partially described elsewhere.

Next the resulting spectrum is exposed to an two-dimensional inverse fast fourier transform. This is an elaborate function that is capable of converting a signal from the frequency domain into the space/time domain. Readers are referred to signal processing textbooks for further details. Finally the resultant vectors are converted to a series of amplitudes by squaring, adding and then square-rooting their components.

This command is currently in an embryonic state and only affects the creation of filters for fourier transforms. It should not currently be used in the making of one-dimensional filters. It has an effect on these, but this is currently broken, and is subject to change in future versions of the program.

Sets the values of AbandonCosinePhase, AbandonSinePhase, CreateCosineArtefacts and CreateSineArtefacts to zero.

Dithering0 affects the red component of palettes defined using RGB data, the hue component of palettes defined using HSV data and general (within-palette) dithering when making Sprites.

Dithering1 affects the green component of palettes defined using RGB data and the saturation component of palettes defined using HSV data.

Dithering2 affects the blue component of palettes defined using RGB data and the value component of palettes defined using HSV data.

Floyd-Steinberg dithering is available if virtual sprites are being used through the Dithering(FloydSteinberg) command. Note that ScaledDithering(FloydSteinberg) will not usually work.

Depth Result

 16M   0

 32K   Value * 3 / 8

 256   Value / 2

 16    Value

 4     Value * 2

 2     Value * 4

One of the problems with this command (and the one above) emerges when textures using it are animated. Because the height of the highest mountain and the floor of the deepest valley (so to speak) determine the scaling factor to be used, this will be a different factor for different animation frames. An especially high mountain will produce a freak low gain value. This will have the effect of making the rest of the texture appear lower than it would normally be. Depending on the colouring scheme used, this can result in an unsightly flashing effect in the resultant animation. There is no simple fix for this, but truncating high mountains, and using a fixed gain contrast command are both possible.

If called with XFactor and YFactor both equal to &FFFF this command does no processing. Otherwise it performs the action of Resize(XFactor,YFactor).

* Note that by virtue of the nature of its action, this command may destroy the ability of the texture to tessellate unless <Theta> is one of Zero, Ninety, OneHundredAndEighty and TwoHundredAndSeventy (in which case QuickRotate should be used). The discontinuities are introduced at what would normally turn into the edges of the sprite. However, further processing may alter their location. The command is also a bit quick and dirty in that no anti-aliasing techniques are used to smooth the rotation. If multiple rotations are used then this might become a problem, though it may also produce some interesting effects as the number of iterations reaches 100.

# Note that there is no QuickRotateAbout as this can be accomplished with a QuickRotate and a TwoDimensionalShift.

* Note that the memory used in manipulating the first two dimensional buffer is not allocated by default, and this will cause the process of texture generation to use more memory than normal. This is only important in if textures are to be generated in low-memory environments.

The three one-dimensional buffers are used to supply the colour's components.

With the RGB ColourModel, buffer two contains the red component, buffer one contains the green component, and the main buffer containing the blue component.

With the HSV ColourModel, buffer two contains the red component, buffer one contains the green component, and the main buffer containing the blue component.

With the HSV ColourModel, buffer two contains the hue component, buffer one contains the saturation component, and the main buffer contains the value component.

With the HSV ColourModel, buffer two contains the X component, buffer one contains the Y component, and the main buffer contains the Z component.

The virtual sprite contains the data which is to be illuminated, and is used to store the result.