S60 3rd Edition SDK for Symbian OS
Example Applications Guide |
OpenGL ES Pick Select Example
1. About this Example
2. Prerequisites
3. Design and Implementation
This example demonstrates one possible way of implementing object and polygon selection. The example consists of two parts: the first is a single rotating cube, whose polygons can be chosen. The second part consists of two rotating cubes that can be separately chosen. The user can choose the mode from the menu. The example can be extended to any kind of OpenGL ES application, but you might want to look the other example applications as well for how to use other, different kinds of, OpenGL ES features.
This example can be extended to any kind of OpenGL ES application, but you might want to look at the other example applications as well for how to use other, different kinds of, OpenGL ES features.
Only classes used by this example are the basic UI framework baseclasses and the Open GL ES API.
To build and run this example you need to have the S60 SDK installed and working correctly on your computer. You also need basic understanding on how to build S60 applications.
To work with this example application you need basic understanding on how to build S60 applications and basic undestanding of how Symbian (or COE) UI and application framework works. Also basic knowledge on OpenGL or OpenGL ES is required if you wish to modify the example.
In this example, the user can freely move a selection cursor or a cross on the screen and select an object or a surface by pressing the joystick button down. See the source code in PickSelect.cpp for more information about the choosing of the alpha values for the polygon/object. Remember that the color of the polygon (and the alpha value) is determined by the color of the last pixel of the triangle triplet. The picking and selection are implemented using the object’s alpha color values. Although this restricts the usage of, for example, blending, the implementation is quite simple and it gives a hint of how to implement more sophisticated selection methods. When the user presses the joystick button, the cursor’s current location pixel’s alpha value is read and then checked to determine whether the cursor was on any polygon/object. If this is the case, the polygon/object is drawn in white color, otherwise nothing happens.
The application has capability NONE as it only needs the rights to execute and access to the screen.
All Open GL ES examples support various screen modes. The examples also support changing the screen size while the application is running. Note that this support must be coded in the application. This code resides in the container's SizeChanged() method.
This inheritance list is sorted roughly, but not completely, alphabetically:
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