xref: /frameworks/base/docs/html/guide/topics/graphics/opengl.jd

page.title=OpenGL
parent.title=Graphics
parent.link=index.html
@jd:body

<div id="qv-wrapper">
  <div id="qv">
    <h2>In this document</h2>

    <ol>
      <li><a href="#basics">The Basics</a>
        <ol>
           <li><a href="#packages">OpenGL packages</a></li>
        </ol>
      <li><a href="#manifest">Declaring OpenGL Requirements</a></li>
      </li>
      <li><a href="#coordinate-mapping">Mapping Coordinates for Drawn Objects</a>
        <ol>
          <li><a href="#proj-es1">Projection and camera in ES 1.0</a></li>
          <li><a href="#proj-es1">Projection and camera in ES 2.0</a></li>
        </ol>
      </li>
      <li><a href="#faces-winding">Shape Faces and Winding</li>
      <li><a href="#compatibility">OpenGL Versions and Device Compatibility</a>
        <ol>
          <li><a href="#textures">Texture compression support</a></li>
          <li><a href="#gl-extension-query">Determining OpenGL Extensions</a></li>
        </ol>
      </li>
      <li><a href="#choosing-version">Choosing an OpenGL API Version</a></li>
    </ol>
    <h2>Key classes</h2>
    <ol>
      <li>{@link android.opengl.GLSurfaceView}</li>
      <li>{@link android.opengl.GLSurfaceView.Renderer}</li>
    </ol>
    <h2>Related samples</h2>
    <ol>
      <li><a href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/graphics/GLSurfaceViewActivity.html">GLSurfaceViewActivity</a></li>
      <li><a href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/graphics/GLES20Activity.html">GLES20Activity</a></li>
      <li><a href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/graphics/TouchRotateActivity.html">TouchRotateActivity</a></li>
      <li><a
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/graphics/CompressedTextureActivity.html">Compressed Textures</a></li>
    </ol>
    <h2>See also</h2>
    <ol>
      <li><a href="{@docRoot}training/graphics/opengl/index.html">
          Displaying Graphics with OpenGL ES</a></li>
      <li><a href="http://www.khronos.org/opengles/">OpenGL ES</a></li>
      <li><a href="http://www.khronos.org/opengles/1_X/">OpenGL ES 1.x Specification</a></li>
      <li><a href="http://www.khronos.org/opengles/2_X/">OpenGL ES 2.x specification</a></li>
    </ol>
  </div>
</div>

<p>Android includes support for high performance 2D and 3D graphics with the Open Graphics Library
(OpenGL), specifically, the OpenGL ES API. OpenGL is a cross-platform graphics API that specifies a
standard software interface for 3D graphics processing hardware. OpenGL ES is a flavor of the OpenGL
specification intended for embedded devices. The OpenGL ES 1.0 and 1.1 API specifications have been
supported since Android 1.0. Beginning with Android 2.2 (API Level 8), the framework supports the
OpenGL ES 2.0 API specification.</p>

<p class="note"><b>Note:</b> The specific API provided by the Android framework is similar to the
  J2ME JSR239 OpenGL ES  API, but is not identical. If you are familiar with J2ME JSR239
  specification, be alert for variations.</p>


<h2 id="basics">The Basics</h2>

<p>Android supports OpenGL both through its framework API and the Native Development
Kit (NDK). This topic focuses on the Android framework interfaces. For more information about the
NDK, see the <a href="{@docRoot}tools/sdk/ndk/index.html">Android NDK</a>.

<p>There are two foundational classes in the Android framework that let you create and manipulate
graphics with the OpenGL ES API: {@link android.opengl.GLSurfaceView} and {@link
android.opengl.GLSurfaceView.Renderer}. If your goal is to use OpenGL in your Android application,
understanding how to implement these classes in an activity should be your first objective.
</p>

<dl>
  <dt><strong>{@link android.opengl.GLSurfaceView}</strong></dt>
  <dd>This class is a {@link android.view.View} where you can draw and manipulate objects using
    OpenGL API calls and is similar in function to a {@link android.view.SurfaceView}. You can use
    this class by creating an instance of {@link android.opengl.GLSurfaceView} and adding your
    {@link android.opengl.GLSurfaceView.Renderer Renderer} to it. However, if you want to capture
    touch screen events, you should extend the {@link android.opengl.GLSurfaceView} class to
    implement the touch listeners, as shown in OpenGL Tutorials for
    <a href="{@docRoot}resources/tutorials/opengl/opengl-es10.html#touch">ES 1.0</a>,
    <a href="{@docRoot}resources/tutorials/opengl/opengl-es20.html#touch">ES 2.0</a> and the <a
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/graphics/TouchRotateActivity.html"
>TouchRotateActivity</a> sample.</dd>

  <dt><strong>{@link android.opengl.GLSurfaceView.Renderer}</strong></dt>
  <dd>This interface defines the methods required for drawing graphics in an OpenGL {@link
    android.opengl.GLSurfaceView}. You must provide an implementation of this interface as a
    separate class and attach it to your {@link android.opengl.GLSurfaceView} instance using
    {@link android.opengl.GLSurfaceView#setRenderer(android.opengl.GLSurfaceView.Renderer)
    GLSurfaceView.setRenderer()}.

    <p>The {@link android.opengl.GLSurfaceView.Renderer} interface requires that you implement the
      following methods:</p>
    <ul>
      <li>
        {@link
    android.opengl.GLSurfaceView.Renderer#onSurfaceCreated(javax.microedition.khronos.opengles.GL10,
    javax.microedition.khronos.egl.EGLConfig) onSurfaceCreated()}: The system calls this
    method once, when creating the {@link android.opengl.GLSurfaceView}. Use this method to perform
    actions that need to happen only once, such as setting OpenGL environment parameters or
    initializing OpenGL graphic objects.
      </li>
      <li>
        {@link
        android.opengl.GLSurfaceView.Renderer#onDrawFrame(javax.microedition.khronos.opengles.GL10)
        onDrawFrame()}: The system calls this method on each redraw of the {@link
        android.opengl.GLSurfaceView}. Use this method as the primary execution point for
        drawing (and re-drawing) graphic objects.</li>
      <li>
        {@link
    android.opengl.GLSurfaceView.Renderer#onSurfaceChanged(javax.microedition.khronos.opengles.GL10,
    int, int) onSurfaceChanged()}: The system calls this method when the {@link
    android.opengl.GLSurfaceView} geometry changes, including changes in size of the {@link
    android.opengl.GLSurfaceView} or orientation of the device screen. For example, the system calls
    this method when the device changes from portrait to landscape orientation. Use this method to
    respond to changes in the {@link android.opengl.GLSurfaceView} container.
      </li>
    </ul>
    </dd>
</dl>

<h3 id="packages">OpenGL packages</h3>
<p>Once you have established a container view for OpenGL using {@link
android.opengl.GLSurfaceView} and {@link android.opengl.GLSurfaceView.Renderer}, you can begin
calling OpenGL APIs using the following classes:</p>

<ul>
  <li>OpenGL ES 1.0/1.1 API Packages
    <ul>
        <li>{@link android.opengl} - This package provides a static interface to the OpenGL ES
1.0/1.1 classes and better performance than the javax.microedition.khronos package interfaces.
          <ul>
            <li>{@link android.opengl.GLES10}</li>
            <li>{@link android.opengl.GLES10Ext}</li>
            <li>{@link android.opengl.GLES11}</li>
            <li>{@link android.opengl.GLES10Ext}</li>
          </ul>
        </li>
      <li>{@link javax.microedition.khronos.opengles} - This package provides the standard
implementation of OpenGL ES 1.0/1.1.
          <ul>
            <li>{@link javax.microedition.khronos.opengles.GL10}</li>
            <li>{@link javax.microedition.khronos.opengles.GL10Ext}</li>
            <li>{@link javax.microedition.khronos.opengles.GL11}</li>
            <li>{@link javax.microedition.khronos.opengles.GL11Ext}</li>
            <li>{@link javax.microedition.khronos.opengles.GL11ExtensionPack}</li>
          </ul>
        </li>
      </ul>
  </li>
  <li>OpenGL ES 2.0 API Class
    <ul>
      <li>{@link android.opengl.GLES20 android.opengl.GLES20} - This package provides the
interface to OpenGL ES 2.0 and is available starting with Android 2.2 (API Level 8).</li>
    </ul>
  </li>
</ul>

<p>If you'd like to start building an app with OpenGL right away, have a look at the tutorials for
<a href="{@docRoot}resources/tutorials/opengl/opengl-es10.html">OpenGL ES 1.0</a> or
<a href="{@docRoot}resources/tutorials/opengl/opengl-es20.html">OpenGL ES 2.0</a>!
</p>

<h2 id="manifest">Declaring OpenGL Requirements</h2>
<p>If your application uses OpenGL features that are not available on all devices, you must include
these requirements in your <a
href="{@docRoot}guide/topics/manifest/manifest-intro.html">AndroidManifest.xml</a></code> file.
Here are the most common OpenGL manifest declarations:</p>

<ul>
  <li><strong>OpenGL ES version requirements</strong> - If your application only supports OpenGL ES
2.0, you must declare that requirement by adding the following settings to your manifest as
shown below.

<pre>
    &lt;!-- Tell the system this app requires OpenGL ES 2.0. --&gt;
    &lt;uses-feature android:glEsVersion="0x00020000" android:required="true" /&gt;
</pre>

  <p>Adding this declaration causes Google Play to restrict your application from being
  installed on devices that do not support OpenGL ES 2.0.</p>
  </li>
  <li><strong>Texture compression requirements</strong> - If your application uses texture
compression formats, you must declare the formats your application supports in your manifest file
using <a href="{@docRoot}guide/topics/manifest/supports-gl-texture-element.html">{@code
&lt;supports-gl-texture&gt;}</a>. For more information about available texture compression
formats, see <a href="#textures">Texture compression support</a>.

<p>Declaring texture compression requirements in your manifest hides your application from users
with devices that do not support at least one of your declared compression types. For more
information on how Google Play filtering works for texture compressions, see the <a
href="{@docRoot}guide/topics/manifest/supports-gl-texture-element.html#market-texture-filtering">
Google Play and texture compression filtering</a> section of the {@code
&lt;supports-gl-texture&gt;} documentation.</p>
  </li>
</ul>


<h2 id="coordinate-mapping">Mapping Coordinates for Drawn Objects</h2>

<p>One of the basic problems in displaying graphics on Android devices is that their screens can
vary in size and shape. OpenGL assumes a square, uniform coordinate system and, by default, happily
draws those coordinates onto your typically non-square screen as if it is perfectly square.</p>

<img src="{@docRoot}images/opengl/coordinates.png">
<p class="img-caption">
  <strong>Figure 1.</strong> Default OpenGL coordinate system (left) mapped to a typical Android
device screen (right).
</p>

<p>The illustration above shows the uniform coordinate system assumed for an OpenGL frame on the
left, and how these coordinates actually map to a typical device screen in landscape orientation
on the right. To solve this problem, you can apply OpenGL projection modes and camera views to
transform coordinates so your graphic objects have the correct proportions on any display.</p>

<p>In order to apply projection and camera views, you create a projection matrix and a camera view
matrix and apply them to the OpenGL rendering pipeline. The projection matrix recalculates the
coordinates of your graphics so that they map correctly to Android device screens. The camera view
matrix creates a transformation that renders objects from a specific eye position.</p>

<h3 id="proj-es1">Projection and camera view in OpenGL ES 1.0</h3>
<p>In the ES 1.0 API, you apply projection and camera view by creating each matrix and then
adding them to the OpenGL environment.</p>

<ol>
<li><strong>Projection matrix</strong> - Create a projection matrix using the geometry of the
device screen in order to recalculate object coordinates so they are drawn with correct proportions.
The following example code demonstrates how to modify the {@link
android.opengl.GLSurfaceView.Renderer#onSurfaceChanged(javax.microedition.khronos.opengles.GL10,
int, int) onSurfaceChanged()} method of a {@link android.opengl.GLSurfaceView.Renderer}
implementation to create a projection matrix based on the screen's aspect ratio and apply it to the
OpenGL rendering environment.

<pre>
  public void onSurfaceChanged(GL10 gl, int width, int height) {
      gl.glViewport(0, 0, width, height);

      // make adjustments for screen ratio
      float ratio = (float) width / height;
      gl.glMatrixMode(GL10.GL_PROJECTION);        // set matrix to projection mode
      gl.glLoadIdentity();                        // reset the matrix to its default state
      gl.glFrustumf(-ratio, ratio, -1, 1, 3, 7);  // apply the projection matrix
  }
</pre>
</li>

<li><strong>Camera transformation matrix</strong> - Once you have adjusted the coordinate system
using a projection matrix, you must also apply a camera view. The following example code shows how
to modify the {@link
android.opengl.GLSurfaceView.Renderer#onDrawFrame(javax.microedition.khronos.opengles.GL10)
onDrawFrame()} method of a {@link android.opengl.GLSurfaceView.Renderer}
implementation to apply a model view and use the
{@link android.opengl.GLU#gluLookAt(javax.microedition.khronos.opengles.GL10, float, float, float,
float, float, float, float, float, float) GLU.gluLookAt()} utility to create a viewing tranformation
which simulates a camera position.

<pre>
    public void onDrawFrame(GL10 gl) {
        ...
        // Set GL_MODELVIEW transformation mode
        gl.glMatrixMode(GL10.GL_MODELVIEW);
        gl.glLoadIdentity();                      // reset the matrix to its default state

        // When using GL_MODELVIEW, you must set the camera view
        GLU.gluLookAt(gl, 0, 0, -5, 0f, 0f, 0f, 0f, 1.0f, 0.0f);
        ...
    }
</pre>
</li>
</ol>

<p>For a complete example of how to apply projection and camera views with OpenGL ES 1.0, see the <a
href="{@docRoot}resources/tutorials/opengl/opengl-es10.html#projection-and-views">OpenGL ES 1.0
tutorial</a>.</p>


<h3 id="proj-es2">Projection and camera view in OpenGL ES 2.0</h3>
<p>In the ES 2.0 API, you apply projection and camera view by first adding a matrix member to
the vertex shaders of your graphics objects. With this matrix member added, you can then
generate and apply projection and camera viewing matrices to your objects.</p>

<ol>
<li><strong>Add matrix to vertex shaders</strong> - Create a variable for the view projection matrix
and include it as a multiplier of the shader's position. In the following example vertex shader
code, the included {@code uMVPMatrix} member allows you to apply projection and camera viewing
matrices to the coordinates of objects that use this shader.

<pre>
    private final String vertexShaderCode =

        // This matrix member variable provides a hook to manipulate
        // the coordinates of objects that use this vertex shader
        "uniform mat4 uMVPMatrix;   \n" +

        "attribute vec4 vPosition;  \n" +
        "void main(){               \n" +

        // the matrix must be included as part of gl_Position
        " gl_Position = uMVPMatrix * vPosition; \n" +

        "}  \n";
</pre>
  <p class="note"><strong>Note:</strong> The example above defines a single transformation matrix
member in the vertex shader into which you apply a combined projection matrix and camera view
matrix. Depending on your application requirements, you may want to define separate projection
matrix and camera viewing matrix members in your vertex shaders so you can change them
independently.</p>
</li>
<li><strong>Access the shader matrix</strong> - After creating a hook in your vertex shaders to
apply projection and camera view, you can then access that variable to apply projection and
camera viewing matrices. The following code shows how to modify the {@link
android.opengl.GLSurfaceView.Renderer#onSurfaceCreated(javax.microedition.khronos.opengles.GL10,
javax.microedition.khronos.egl.EGLConfig) onSurfaceCreated()} method of a {@link
android.opengl.GLSurfaceView.Renderer} implementation to access the matrix
variable defined in the vertex shader above.

<pre>
    public void onSurfaceCreated(GL10 unused, EGLConfig config) {
        ...
        muMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix");
        ...
    }
</pre>
</li>
<li><strong>Create projection and camera viewing matrices</strong> - Generate the projection and
viewing matrices to be applied the graphic objects. The following example code shows how to modify
the {@link
android.opengl.GLSurfaceView.Renderer#onSurfaceCreated(javax.microedition.khronos.opengles.GL10,
javax.microedition.khronos.egl.EGLConfig) onSurfaceCreated()} and {@link
android.opengl.GLSurfaceView.Renderer#onSurfaceChanged(javax.microedition.khronos.opengles.GL10,
int, int) onSurfaceChanged()} methods of a {@link android.opengl.GLSurfaceView.Renderer}
implementation to create camera view matrix and a projection matrix based on the screen aspect ratio
of the device.

<pre>
    public void onSurfaceCreated(GL10 unused, EGLConfig config) {
        ...
        // Create a camera view matrix
        Matrix.setLookAtM(mVMatrix, 0, 0, 0, -3, 0f, 0f, 0f, 0f, 1.0f, 0.0f);
    }

    public void onSurfaceChanged(GL10 unused, int width, int height) {
        GLES20.glViewport(0, 0, width, height);

        float ratio = (float) width / height;

        // create a projection matrix from device screen geometry
        Matrix.frustumM(mProjMatrix, 0, -ratio, ratio, -1, 1, 3, 7);
    }
</pre>
</li>

<li><strong>Apply projection and camera viewing matrices</strong> - To apply the projection and
camera view transformations, multiply the matrices together and then set them into the vertex
shader. The following example code shows how modify the {@link
android.opengl.GLSurfaceView.Renderer#onDrawFrame(javax.microedition.khronos.opengles.GL10)
onDrawFrame()} method of a {@link android.opengl.GLSurfaceView.Renderer} implementation to combine
the projection matrix and camera view created in the code above and then apply it to the graphic
objects to be rendered by OpenGL.

<pre>
    public void onDrawFrame(GL10 unused) {
        ...
        // Combine the projection and camera view matrices
        Matrix.multiplyMM(mMVPMatrix, 0, mProjMatrix, 0, mVMatrix, 0);

        // Apply the combined projection and camera view transformations
        GLES20.glUniformMatrix4fv(muMVPMatrixHandle, 1, false, mMVPMatrix, 0);

        // Draw objects
        ...
    }
</pre>
</li>
</ol>
<p>For a complete example of how to apply projection and camera view with OpenGL ES 2.0, see the <a
href="{@docRoot}resources/tutorials/opengl/opengl-es20.html#projection-and-views">OpenGL ES 2.0
tutorial</a>.</p>

<h2 id="faces-winding">Shape Faces and Winding</h2>

<p>In OpenGL, the face of a shape is a surface defined by three or more points in three-dimensional
space. A set of three or more three-dimensional points (called vertices in OpenGL) have a front face
and a back face. How do you know which face is front and which is the back? Good question. The
answer has to do with winding, or, the direction in which you define the points of a shape.</p>

<img src="{@docRoot}images/opengl/ccw-winding.png">
<p class="img-caption">
  <strong>Figure 1.</strong> Illustration of a coordinate list which translates into a
counterclockwise drawing order.</p>

<p>In this example, the points of the triangle are defined in an order such that they are drawn in a
counterclockwise direction. The order in which these coordinates are drawn defines the winding
direction for the shape. By default, in OpenGL, the face which is drawn counterclockwise is the
front face. The triangle shown in Figure 1 is defined so that you are looking at the front face of
the shape (as interpreted by OpenGL) and the other side is the back face.</p>

<p>Why is it important to know which face of a shape is the front face? The answer has to do with a
commonly used feature of OpenGL, called face culling. Face culling is an option for the OpenGL
environment which allows the rendering pipeline to ignore (not calculate or draw) the back face of a
shape, saving time, memory and processing cycles:</p>

<pre>
// enable face culling feature
gl.glEnable(GL10.GL_CULL_FACE);
// specify which faces to not draw
gl.glCullFace(GL10.GL_BACK);
</pre>

<p>If you try to use the face culling feature without knowing which sides of your shapes are the
front and back, your OpenGL graphics are going to look a bit thin, or possibly not show up at all.
So, always define the coordinates of your OpenGL shapes in a counterclockwise drawing order.</p>

<p class="note"><strong>Note:</strong> It is possible to set an OpenGL environment to treat the
clockwise face as the front face, but doing so requires more code and is likely to confuse
experienced OpenGL developers when you ask them for help. So don’t do that.</p>

<h2 id="compatibility">OpenGL Versions and Device Compatibility</h2>

<p>The OpenGL ES 1.0 and 1.1 API specifications have been supported since Android 1.0.
Beginning with Android 2.2 (API Level 8), the framework supports the OpenGL ES 2.0 API
specification. OpenGL ES 2.0 is supported by most Android devices and is recommended for new
applications being developed with OpenGL. For information about the relative number of
Android-powered devices that support a given version of OpenGL ES, see the <a
href="{@docRoot}resources/dashboard/opengl.html">OpenGL ES Versions Dashboard</a>.</p>


<h3 id="textures">Texture compression support</h3>
<p>Texture compression can significantly increase the performance of your OpenGL application by
reducing memory requirements and making more efficient use of memory bandwidth. The Android
framework provides support for the ETC1 compression format as a standard feature, including a {@link
android.opengl.ETC1Util} utility class and the {@code etc1tool} compression tool (located in the
Android SDK at {@code &lt;sdk&gt;/tools/}). For an example of an Android application that uses
texture compression, see the <a
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/graphics/CompressedTextureActivity.html"
>CompressedTextureActivity</a> code sample.</p>

<p>The ETC format is supported by most Android devices, but it not guarranteed to be available. To
check if the ETC1 format is supported on a device, call the {@link
android.opengl.ETC1Util#isETC1Supported() ETC1Util.isETC1Supported()} method.</p>

<p class="note"><b>Note:</b> The ETC1 texture compression format does not support textures with an
alpha channel. If your application requires textures with an alpha channel, you should
investigate other texture compression formats available on your target devices.</p>

<p>Beyond the ETC1 format, Android devices have varied support for texture compression based on
their GPU chipsets and OpenGL implementations. You should investigate texture compression support on
the the devices you are are targeting to determine what compression types your application should
support. In order to determine what texture formats are supported on a given device, you must <a
href="#gl-extension-query">query the device</a> and review the <em>OpenGL extension names</em>,
which identify what texture compression formats (and other OpenGL features) are supported by the
device. Some commonly supported texture compression formats are as follows:</p>

<ul>
  <li><strong>ATITC (ATC)</strong> - ATI texture compression (ATITC or ATC) is available on a
wide variety of devices and supports fixed rate compression for RGB textures with and without
an alpha channel. This format may be represented by several OpenGL extension names, for example:
    <ul>
      <li>{@code GL_AMD_compressed_ATC_texture}</li>
      <li>{@code GL_ATI_texture_compression_atitc}</li>
    </ul>
  </li>
  <li><strong>PVRTC</strong> - PowerVR texture compression (PVRTC) is available on a wide
variety of devices and supports 2-bit and 4-bit per pixel textures with or without an alpha channel.
This format is represented by the following OpenGL extension name:
    <ul>
      <li>{@code GL_IMG_texture_compression_pvrtc}</li>
    </ul>
  </li>
  <li><strong>S3TC (DXT<em>n</em>/DXTC)</strong> - S3 texture compression (S3TC) has several
format variations (DXT1 to DXT5) and is less widely available. The format supports RGB textures with
4-bit alpha or 8-bit alpha channels. This format may be represented by several OpenGL extension
names, for example:
    <ul>
      <li>{@code GL_OES_texture_compression_S3TC}</li>
      <li>{@code GL_EXT_texture_compression_s3tc}</li>
      <li>{@code GL_EXT_texture_compression_dxt1}</li>
      <li>{@code GL_EXT_texture_compression_dxt3}</li>
      <li>{@code GL_EXT_texture_compression_dxt5}</li>
    </ul>
  </li>
  <li><strong>3DC</strong> - 3DC texture compression (3DC) is a less widely available format that
supports RGB textures with an an alpha channel. This format is represented by the following OpenGL
extension name:</li>
    <ul>
      <li>{@code GL_AMD_compressed_3DC_texture}</li>
    </ul>
</ul>

<p class="warning"><strong>Warning:</strong> These texture compression formats are <em>not
supported</em> on all devices. Support for these formats can vary by manufacturer and device. For
information on how to determine what texture compression formats are on a particular device, see
the next section.
</p>

<p class="note"><strong>Note:</strong> Once you decide which texture compression formats your
application will support, make sure you declare them in your manifest using <a
href="{@docRoot}guide/topics/manifest/supports-gl-texture-element.html">&lt;supports-gl-texture&gt;
</a>. Using this declaration enables filtering by external services such as Google Play, so that
your app is installed only on devices that support the formats your app requires. For details, see
<a
href="{@docRoot}guide/topics/graphics/opengl.html#manifest">OpenGL manifest declarations</a>.</p>

<h3 id="gl-extension-query">Determining OpenGL extensions</h3>
<p>Implementations of OpenGL vary by Android device in terms of the extensions to the OpenGL ES API
that are supported. These extensions include texture compressions, but typically also include other
extensions to the OpenGL feature set.</p>

<p>To determine what texture compression formats, and other OpenGL extensions, are supported on a
particular device:</p>
<ol>
  <li>Run the following code on your target devices to determine what texture compression
formats are supported:
<pre>
  String extensions = javax.microedition.khronos.opengles.GL10.glGetString(GL10.GL_EXTENSIONS);
</pre>
  <p class="warning"><b>Warning:</b> The results of this call <em>vary by device!</em> You
must run this call on several target devices to determine what compression types are commonly
supported.</p>
  </li>
  <li>Review the output of this method to determine what OpenGL extensions are supported on the
device.</li>
</ol>


<h2 id="choosing-version">Choosing an OpenGL API Version</h2>

<p>OpenGL ES API version 1.0 (and the 1.1 extensions) and version 2.0 both provide high
performance graphics interfaces for creating 3D games, visualizations and user interfaces. Graphics
programming for the OpenGL ES 1.0/1.1 API versus ES 2.0 differs significantly, and so developers
should carefully consider the following factors before starting development with either API:</p>

<ul>
  <li><strong>Performance</strong> - In general, OpenGL ES 2.0 provides faster graphics performance
than the ES 1.0/1.1 APIs. However, the performance difference can vary depending on the Android
device your OpenGL application is running on, due to differences in the implementation of the OpenGL
graphics pipeline.</li>
  <li><strong>Device Compatibility</strong> - Developers should consider the types of devices,
Android versions and the OpenGL ES versions available to their customers. For more information
on OpenGL compatibility across devices, see the <a href="#compatibility">OpenGL Versions and Device
Compatibility</a> section.</li>
  <li><strong>Coding Convenience</strong> - The OpenGL ES 1.0/1.1 API provides a fixed function
pipeline and convenience functions which are not available in the ES 2.0 API. Developers who are new
to OpenGL may find coding for OpenGL ES 1.0/1.1 faster and more convenient.</li>
  <li><strong>Graphics Control</strong> - The OpenGL ES 2.0 API provides a higher degree
of control by providing a fully programmable pipeline through the use of shaders. With more
direct control of the graphics processing pipeline, developers can create effects that would be
very difficult to generate using the 1.0/1.1 API.</li>
</ul>

<p>While performance, compatibility, convenience, control and other factors may influence your
decision, you should pick an OpenGL API version based on what you think provides the best experience
for your users.</p>