Add a description for using extensions and a description of the generic protocol configuration file
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91
docs-mini/README.extensions
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91
docs-mini/README.extensions
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Using Extensions
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----------------
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To use an OpenGL extension in the code is is necessary to include a refference
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to the extensions.hxx header file and add the following to the code (as an
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example):
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/* global variables */
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glPointParameterfProc glPointParameterfPtr = 0;
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glPointParameterfvProc glPointParameterfvPtr = 0;
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bool glPointParameterIsSupported = false;
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To be able to use these extensions the functions pointers have to be initialized
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by something like the following examplde code:
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if (SGIsOpenGLExtensionSupported("GL_EXT_point_parameters") )
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{
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glPointParameterIsSupported = true;
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glPointParameterfPtr = (glPointParameterfProc)
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SGLookupFunction("glPointParameterfEXT");
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glPointParameterfvPtr = (glPointParameterfvProc)
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SGLookupFunction("glPointParameterfvEXT");
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} else if ( SGIsOpenGLExtensionSupported("GL_ARB_point_parameters") ) {
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glPointParameterIsSupported = true;
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glPointParameterfPtr = (glPointParameterfProc)
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SGLookupFunction("glPointParameterfARB");
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glPointParameterfvPtr = (glPointParameterfvProc)
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SGLookupFunction("glPointParameterfvARB");
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} else
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glPointParameterIsSupported = false;
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If a function is supported the function pointers are now initialized.
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When using the functions (note that glPointParameterfvPtr() is used instead of
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glPointParameterfvEXT() )it is important to check whether the
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glPointParameterIsSupported is set to true:
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if ( distance_attenuation && glPointParameterIsSupported )
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{
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// Enable states for drawing points with GL_extension
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glEnable(GL_POINT_SMOOTH);
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float quadratic[3] = {1.0, 0.001, 0.0000001};
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// makes the points fade as they move away
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glPointParameterfvPtr(GL_DISTANCE_ATTENUATION_EXT, quadratic);
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glPointParameterfPtr(GL_POINT_SIZE_MIN_EXT, 1.0);
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}
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Adding Extensions
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-----------------
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To add an extension to the SimGear extension support code you normally only need
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to edit the extensions.hxx header file in the screen directory.
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Currently there are two extensions supported:
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* glPointParameterf
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* glActiveTexture
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Adding a new extension involves adding the defines assosiated with the extension
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(surrounded by the appropriate extension test):
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#ifndef GL_EXT_point_parameters
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# define GL_EXT_point_parameters 1
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# define GL_POINT_SIZE_MIN_EXT 0x8126
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# define GL_DISTANCE_ATTENUATION_EXT 0x8129
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#endif
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This is needed because not all OpenGL implementations define them correctly.
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The following step is to add a typedef for the function pointer:
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typedef void (APIENTRY * glPointParameterfProc)(GLenum pname, GLfloat param);
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The APIENTRY refference is only used by windows machines but is defined empty
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for all other platforms and hence needs to be added for cross platfrom
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compatibillity.
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81
docs-mini/README.protocol
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81
docs-mini/README.protocol
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The generic communication protocol for FlightGear provides a powerfull way
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of adding a simple ASCII based output only protocol, just by defining an
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XML encoded configuration file and placing it in the $FG_ROOT/data/Protocols
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directory.
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The definition of the protocol consists of variable separators, line separators,
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and chuncks of text.
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Each chunck defines:
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<name> for ease of use
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<node> the property tree node which provides the data
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<type> the value type (needed for formatting)
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<format> defines the actual piece of text which should be sent.
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it can include formatting options like:
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<type>
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%s string
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%i integer (default)
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%f float
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<factor> an optionale multiplication factor which can be used for
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unit conversion. (for example, radians to degrees).
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<offset> an optional offset which can be used for unit conversion.
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(for example, degrees Celsius to degrees Fahrenheit).
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The output section also could define the variable separator and line separator.
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The separators can be either a control character such as a tab or newline, or a
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user specified string or other single charachter. The currently supported
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control charachters are:
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<var_separator>:
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<line_separator>:
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Name Charachter
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newline '\n'
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tab '\t'
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formfeed '\f'
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carriagereturn '\r'
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verticaltab '\v'
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any other charachters just need to be added to "Network/generic.cxx"
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The var_separator is placed between each variable, while the line_separator is
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placed at the end of each lot of variables.
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A simple protocol configuration file then could look something like the
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following:
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<?xml version="1.0"?>
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<PropertyList>
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<output>
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<line_separator>newline</line_separator>
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<var_separator>newline</var_separator>
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<chunk>
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<name>speed</name>
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<format>V=%d</format>
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<node>/velocities/airspeed-kt</node>
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</chunk>
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<chunk>
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<name>heading (rad)</name>
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<format>H=%02d</format>
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<node>/orientation/heading-deg</node>
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<factor>57.29578</factor> <!-- degrees to radians -->
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</chunk>
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<chunk>
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<name>pitch angle (deg)</name>
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<format>P=%05.1f</format>
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<type>float</type>
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<node>/orientation/pitch-deg</node>
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</chunk>
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</output>
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</PropertyList>
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