Howto:Use a Camera View in an Instrument: Difference between revisions
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* implement the interface for the od_gauge instrument to dynamically create a texture and display update it as a cockpit instrument | * implement the interface for the od_gauge instrument to dynamically create a texture and display update it as a cockpit instrument | ||
* implement SGPropertyChangeListener to process property tree events and updates [http://simgear.sourceforge.net/doxygen/classSGPropertyChangeListener.html] | * implement SGPropertyChangeListener to process property tree events and updates [http://simgear.sourceforge.net/doxygen/classSGPropertyChangeListener.html] | ||
* Render a property-driven camera view to the created texture (Zan has already code doing this sort of thing | * Render a property-driven camera view to the created texture (Zan has already code doing this sort of thing {{forum link|t=13798}}) | ||
* Write an XML 2D Instrument file that displays the texture | * Write an XML 2D Instrument file that displays the texture | ||
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* [http://thermalpixel.github.io/osg/2014/02/15/rtt-with-slave-cameras.html OSG RTT with Slave Cameras] | * [http://thermalpixel.github.io/osg/2014/02/15/rtt-with-slave-cameras.html OSG RTT with Slave Cameras] | ||
* | * {{forum link|t=15797|text=External camera for periscope}} | ||
* | * {{forum link|t=13798|text=Zan's work on improved camera config options}} | ||
* | * {{forum link|p=184284|text=Rear-View Mirror?}} | ||
* | * {{forum link|t=13798|text=Improved camera configuration options}} | ||
* | * {{forum link|t=6184|text=Mirrors}} | ||
* | * {{forum link|p=31252|text=Rallye MS-893 in development}} | ||
[[Category:GSoC]] | [[Category:GSoC]] | ||
[[Category: Core development projects]] | [[Category: Core development projects]] |
Revision as of 16:35, 7 June 2019
IMPORTANT: Some, and possibly most, of the features/ideas discussed here are likely to be affected, and possibly even deprecated, by the ongoing work on providing a property tree-based 2D drawing API accessible from Nasal using the new Canvas system available since FlightGear 2.80 (08/2012). Please see: Canvas Development#Supporting Cameras for further information
You are advised not to start working on anything directly related to this without first discussing/coordinating your ideas with other FlightGear contributors using the FlightGear developers mailing list or the Canvas subforum . Anything related to Canvas Core Development should be discussed first of all with TheTom and Zakalawe. Nasal-space frameworks are being maintained by Philosopher and Hooray currently. talk page. |
Background
Note There is a related patch available at https://forum.flightgear.org/viewtopic.php?p=317448#p317448 |
This was inspired by the ongoing effort to create a realistic 787 for FlightGear, including support for rendering external camera views on instruments: Boeing 787-8 Dreamliner#Camera.2FVideo Surveillance Instrument. The "Tail Camera" is also a feature found on the A380.
Objective
To create a 2D instrument which shows a camera view. Write C++ code, preferably an instrument that renders a Camera View (i.e. from the property tree) to a texture.
The steps involved in creating such an instrument would be:*
- create a new topic branch: FlightGear and Git#Local_Branch
- Add a new set of cxx/hxx files to $FG_SRC/Instrumentation/ (e.g. camera-texture.cxx and camera-texture.hxx): to get started quickly, just copy and customize the gyro.* files
- implement the SGSubsystem interface for the new subsystem [1]
- add the new files to the CMake build system: Developing using CMake#Adding_new_files_to_the_build
- add the new subsystem to the instrument_mgr (FGInstrumentMgr::build method)[2]
- implement the interface for the od_gauge instrument to dynamically create a texture and display update it as a cockpit instrument
- implement SGPropertyChangeListener to process property tree events and updates [3]
- Render a property-driven camera view to the created texture (Zan has already code doing this sort of thing [4] )
- Write an XML 2D Instrument file that displays the texture
There are obviously more steps involved here, some of which covered here Howto: Create a 2D drawing API for FlightGear.
Pre-Requisites
The following are required before we continue...
- To be able to build FlightGear from Source (with or without an IDE)
- To be able to create new instruments (that would be taking a simple one like gyro, copying it's files and changing the content)
- A Gitorious account to be able to clone the Flightgear Repository
- Basic Knowledge of FlightGear and XML
osgViewer::CompositeViewer
This section has been moved to a dedicated article: CompositeViewer Support.
Part 1: Rendering a Camera View to Texture
There're probably many ways to do that, you could do it the way the ground radar instrument does, or how you take a screenshot etc.
A couple nice guides on OpenSceneGraph Rendering are available at:
- http://beefdev.blogspot.de/2012/01/render-to-texture-in-openscenegraph.html
- http://www.palomino3d.org/pal/openscenegraph.php
- http://sourceforge.net/apps/mediawiki/delta3d/index.php?title=Tutorial_Render_To_Texture
The OSG Quick Start guide can be download at: http://www.lulu.com/items/volume_51/767000/767629/3/print/OSGQSG.pdf
The OSG API reference is available here: http://www.openscenegraph.org/documentation/OpenSceneGraphReferenceDocs/annotated.html
The OpenSceneGraph Beginners Guide is also available on line.
Also see: http://www.openscenegraph.org/projects/osg/wiki/Support/GettingStarted
The OSG FAQ can be found at: http://www.3drealtimesimulation.com/osg/osg_faq_1.htm
Programming Resources#OSG.2FOpenSceneGraph_related
Screenshot Method
This is a very simple method and is used normally for taking screen-shots.
OpenSceneGraph C++ Code:
osg::Image* shot = new osg::Image();
shot->allocateImage(width, height, 24, GL_RGB, GL_UNSIGNED_BYTE);
camera->attach(osg::Camera::COLOR_BUFFER, shot);
osgDB::writeImageFile(*shot,"image_file.png");
FlightGear code
FlighGear already has an "Owner Drawn instrument" in flightgear/src/Instrumentation/od_gauge.cxx and .hxx (this is now in canvas/simgear). It already sets up a pre-render camera and a texture for it, and has a visitor to replace model's texture with the custom texture.
Using it would be something like this:
- Create a custom instrument which inherits od_gauge. class CameraInstrument : public FGODGauge { ... }
- Implement the init and update functions, whatever instrument manager requires.
- In init set up proper texture sizes and call allocRT().
- NOTE: od_gauge does NOT add camera to render the scenery, but a custom model. One needs to modify od_gauge so that allocRT calls globals()->get_renderer()->addCamera(camera.get(), true);
- In update function update camera position according to viewer->getAbsolutePosition(...).
- Add the custom instrument to instrument_mgr.cxx.
Creating the CamView as a hard coded instrument
Header File: cam_display.hxx
The header file is used to simply initialize a new class that contains all functions related to this instrument. The Functions are just constructed here, the contents are put in the cam_display.cxx file.
// cam_display.hxx - simple function to render view to texture
#ifndef __INSTRUMENTATION_CAMVIEW_HXX
#define __INSTRUMENTATION_CAMVIEW_HXX
#include <simgear/props/props.hxx>
#include "od_gauge.hxx"
class CamView : public SGPropertyChangeListener, public FGODGauge
{
public:
static const int TextureHalfSize = 256;
CamView(SGPropertyNode* node);
virtual ~CamView();
void updateTexture();
virtual void valueChanged(SGPropertyNode*);
protected:
void createTexture(const char* texture_name);
};
#endif // __INSTRUMENTATION_CAMVIEW_HXX
Adding the Instrument to 'instrument_mgr.cxx'
Your Instrument's header file, cam_display.hxx is a constructor for the main instrument class, and the functions are further defined in the cam_display.cxx function. Include the cam_display.hxx function in the instrument_mgr.cxx file so it knows where your function is.
#include "cam_display.hxx"
In the FGInstrumentMgr::build function, add an else if statement so that it checks whether your instrument too is called.
else if ( name == "cam_display" ) {
set_subsystem( id, new CamView( node ),1);
}
Part 2: Getting that texture into an instrument
This part doesn't require any C++ coding, just a simple XML script to use that texture in an instrument.
<?xml version="1.0"?>
<PropertyList>
<name>Camera Instrument</name>
<w-base>512</w-base>
<h-base>512</h-base>
<layers>
<layer>
<name>camera</name>
<texture>
<path>image_file.png</path> <!-- Path to the file we just rendered -->
<x1>0</x1>
<y1>0</y1>
<x2>1</x2>
<y2>1</y2>
</texture>
<emissive>1</emissive>
<w>512</w>
<h>512</h>
</layer>
</layers>
</PropertyList>
You could create more layers for more cameras/different views or even have a sprite or something on the view. Or we could also add transformations or conditions to the layer to give some function to the instrument other than just show a camera view.
<transformation>
<type>y-shift</type>
<property>/instrumentation/camera/y_shift</property>
<scale>2</scale>
</transformation>