S60 3rd Edition SDK for Symbian OS
Example Applications Guide

OpenGL ES Environmental Mapping Example

1. About this Example
2. Prerequisites
3. Design and Implementation

1. About this Example

This example demonstrates one possible way of implementing environmental mapping. The example consists of the same two models as used in SimpleLighting example which are environmental mapped. The user can rotate both objects with the joystick.

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. Open GL ES itself is pure C method call API and doesn't use classes.

2. Prerequisites

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.

3. Design and Implementation

Environmental mapping in this example is implemented by using averaged vertex normals (n-vectors) as texture input coordinates. An average vertex normal is calculated by averaging every surface normal that is connected to that particular vertex. The texture coordinates are actually normals, 4D coordinates, where the last value is 1. These coordinate values are given to texture matrix, which rotates them in the same way as the model view matrix does. Output from the texture matrix is also a 4D vector, where only the first two components are used as (u,v) texture coordinates. Since the first three coordinates form a unit vector, also the norm of (u,v) is at most 1, leading to the fact that only a circular area of the texture is used as an environmental map.

Normally the input texture coordinates would be the coordinates of the reflected ray with respect to the object vertex normal. This means that the method implemented in this example gives only an approximation of the reflectance. An advantage is that the averaged normals can be calculated apriori. See the CalculateTextureCoordinates(…) method in file EnvMapping.cpp for additional comments.

The restrictions of implementing the environmental mapping in this way are that we can use only one environmental texture at a time, and only the rotations of the camera and the object are allowed, that is, neither the camera nor object may move around. Both the rotations of the camera and the object are also multiplied within the current texture matrix. See methods DrawDuck(…) and DrawHead(…) for additional information and comments on setting the texture matrix.

3.1 Capabilities

The application has capability NONE as it only needs the rights to execute and access to the screen.

3.2 ScalableUI

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 and this code resides in the container's SizeChanged() method.

This inheritance list is sorted roughly, but not completely, alphabetically: