Class: MD2::Command

Inherits:
Object
  • Object
show all
Defined in:
lib/md2/command.rb

Overview

This class is instantiated from the C extension. You shouldn’t have to instantiate it directly.

GL Commands are an optimization technique employed by MD2 files to improve render time. The MD2 file contains a span of bytes equal to the MD2::Header#gl_command_count. Those bytes in turn have the following format:

1. How many bytes follow for a single GL command. This is an integer, so the data need to be
   cast into an integer in order to be processed.

   This byte also indicates the render method for this GL command: if it's positive,
   this is a triangle strip; if it's negative, a triangle fan. If zero, this byte
   represents the end of the command list. Terminating bytes are silently omitted
   by this Ruby library.
2. The horizontal texture coordinate. This is a float, so the data needs to be cast into a
   float to be processed.
3. The vertical texture coordinate. This is a float, so the data needs to be cast into a
   float to be processed.
4. The vertex index to be rendered. This is an integer, so the data needs to be cast into
   an integer to be processed.

As the data are cast into the necessary types, the boundaries of any given command structure must be adjusted to match. I was not able to find a way to do this using pure Ruby, so the bulk of the above algorithm is implemented in this gem’s C extension.

This class is only instantiated after the fact, with the data already deserialized.

Defined Under Namespace

Classes: Segment

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(args) ⇒ Command

Arguments are expected to be a single array with the following content:

[ (:triangle_strip|:triangle_fan), *elements ]

The remainder of the elements are expected to appear in this order:

(s_coord, t_coord, vert_index)

So, the elements are expected to be in groups of 3: the s and t texture coordinates (which are Floats), and the vertex index (which is a Fixnum).

The array of args is expected to be a single, flat array – the data should not be nested into other arrays.



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# File 'lib/md2/command.rb', line 55

def initialize(args)
  @type = args.shift
  @segments = []
  
  0.step(args.length-1, 3) do |index|
    @segments << MD2::Command::Segment.new(args[index], args[index+1], args[index+2])
  end
end

Instance Attribute Details

#segments ⇒ Object (readonly)

an array of segments, each an instance of MD2::Command::Segment. Segments contain the vertex and texture data for this command.



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# File 'lib/md2/command.rb', line 41

def segments
  @segments
end

#type ⇒ Object (readonly)

The type of command. This is equal to either :triangle_strip or :triangle_fan.



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# File 'lib/md2/command.rb', line 37

def type
  @type
end