NAME
Graphics::GVG - Game Vector GraphicsSYNOPSIS
my $SCRIPT = <<'END';
%color = #FF33FFFF;
line( %color, 0.0, 0.0, 1.0, 1.1 );
glow {
circle( %color, 0, 0, 0.9 );
rect( %color, 0, 1, 0.7, 0.4 );
}
END
my $gvg = Graphics::GVG->new;
my $ast = $gvg->parse( $SCRIPT );DESCRIPTION
Parses scripts that describe vectors used for gaming graphics. The script is parsed into an Abstract Syntax Tree (AST), which can then be transformed into different forms. For example, Graphics::GVG::OpenGLRender generates Perl code that can be compiled and called inside a larger Perl/OpenGL program.
LANGUAGE
Compared to SVG, GVG scripts are very simple. They look like a series of C function calls, with blocks that generate various effects. Each statement is ended by a semicolon.
The coordinate space follows general OpenGL conventions, where x/y coords are floating point numbers between -1.0 and 1.0, using the right-hand rule.
Comments
Comments start with '//' and go to the end of the line
Operators
There aren't any.
Conditionals
There aren't any.
Loops
There aren't any. I said this was a simple language, remember?
Data Types
GVG functions can take several data types:
Integer -- a series of digits with no decimal point, like
1234.Float -- a series of digits, which can contain a decimal point, like
1.234. While you can specify as many digits as you want, note that these are ultimately limited to double-precision IEEE floats.Color -- starts with a '#', and then is followed by 8 hexidecimal digits, in RGBA form, like
#5cd2bbff. Hex digits can be upper or lower case.
Integers and floats can both use '-' to indicate a negative number.
The type system is both static and strong; you can't assign an integer to a color parameter.
Variables
Data types can be saved in variables, which each data type getting its own sigal.
&x = 2; // Integer
$y = 1.23; // Float
%color = #ff33aaff; // Color
poly( %color, 0, $y, 4.3, &x, 30.2 );Variables can be redefined at any time:
%color = #ff33aaff;
line( %color, 0, 1, 1, 0 );
%color = #aabbaaff;
line( %color, 1, 0, 1, 1 );Meta Information
Meta info is general things that renderers may need to work with, and are usually dependent on a larger context. For instance, you might put in a !size = "small";, which might be sized relative to tiny, medium, large, huge, etc. objects in the rest of the system.
Meta statements start with ! and are followed by a name and a value. The value can be a float, integer, or a string (surrounded by double quotes).
!name = "flying thing";
!size = "small";
!side = 1;Functions
There are several drawing functions for defining vectors.
line
line( %color, $x1, $y1, $x2, $y2 );A line of the given %color, going from coordinates $x1,$y1 to $x2,$y2.
circle
circle( %color, $cx, $cy, $r );A circle of the given %color, centered at $cx,$cy, with radius $r.
rect
rect( %color, $x, $y, $width, $height );A rectangle of the given %color, starting at $x,$y, and then going to $x + $width and $y + $height.
ellipse
ellipse( %color, $cx, $cy, $rx, $ry );An ellipse of the given %color, centered at $cx,$cy, with respective radii $rx and $ry.
point
point( %color, $x, $y, $size );A point of the given %color, at $x,$y, with size $size.
poly
poly( %color, $cx, $cy, $r, &sides, $rotate );A regular polygon of the given %color, centered at $cx,$cy, rotated $rotate degrees, with radius $r, and &sides number of sides.
Effects
Effects can be applied to drawing functions by enclosing them in a block (inside {...} characters) named for a certain effect.
For example, a glow effect can be set on lines with:
glow {
circle( %color, 0, 0, 0.9 );
rect( %color, 0, 1, 0.7, 0.4 );
}How this is rendered is dependent on the renderer. An OpenGL renderer may show an actual neon glow effect, while a renderer for a physics library may ignore it entirely.
ABSTRACT SYNTAX TREE
The parse results in an Abstract Syntax Tree, which is represented with Perl objects. Developers writing renderers will need to take the AST and walk it to generate their desired output. See Graphics::GVG::AST for a description of the tree objects.
METHODS
parse
Takes a GVG script as input. On success, returns an abstract syntax tree. Otherwise, throws a fatal error.
LICENSE
Copyright (c) 2016 Timm Murray
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.