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diff --git a/docs/html/training/graphics/opengl/motion.jd b/docs/html/training/graphics/opengl/motion.jd new file mode 100644 index 0000000..6888235 --- /dev/null +++ b/docs/html/training/graphics/opengl/motion.jd @@ -0,0 +1,92 @@ +page.title=Adding Motion +parent.title=Displaying Graphics with OpenGL ES +parent.link=index.html + +trainingnavtop=true +previous.title=Applying Projection and Camera Views +previous.link=projection.html +next.title=Responding to Touch Events +next.link=touch.html + +@jd:body + +<div id="tb-wrapper"> +<div id="tb"> + +<h2>This lesson teaches you to</h2> +<ol> + <li><a href="#rotate-gl1">Rotate a Shape</a></li> + <li><a href="#cont-render">Enable Continuous Rendering</a></li> +</ol> + +<h2>You should also read</h2> +<ul> + <li><a href="{@docRoot}guide/topics/graphics/opengl.html">OpenGL</a></li> +</ul> + +<div class="download-box"> + <a href="http://developer.android.com/shareables/training/OpenGLES.zip" +class="button">Download the sample</a> + <p class="filename">OpenGLES.zip</p> +</div> + +</div> +</div> + +<p>Drawing objects on screen is a pretty basic feature of OpenGL, but you can do this with other +Android graphics framwork classes, including {@link android.graphics.Canvas} and +{@link android.graphics.drawable.Drawable} objects. OpenGL ES provides additional capabilities for +moving and transforming drawn objects in three dimensions or in other unique ways to create +compelling user experiences.</p> + +<p>In this lesson, you take another step forward into using OpenGL ES by learning how to add motion +to a shape with rotation.</p> + + +<h2 id="rotate">Rotate a Shape</h2> + +<p>Rotating a drawing object with OpenGL ES 2.0 is relatively simple. You create another +transformation matrix (a rotation matrix) and then combine it with your projection and +camera view tranformation matrices:</p> + +<pre> +private float[] mRotationMatrix = new float[16]; +public void onDrawFrame(GL10 gl) { + ... + // Create a rotation transformation for the triangle + long time = SystemClock.uptimeMillis() % 4000L; + float angle = 0.090f * ((int) time); + Matrix.setRotateM(mRotationMatrix, 0, mAngle, 0, 0, -1.0f); + + // Combine the rotation matrix with the projection and camera view + Matrix.multiplyMM(mMVPMatrix, 0, mRotationMatrix, 0, mMVPMatrix, 0); + + // Draw triangle + mTriangle.draw(mMVPMatrix); +} +</pre> + +<p>If your triangle does not rotate after making these changes, make sure you have commented out the +{@link android.opengl.GLSurfaceView#RENDERMODE_WHEN_DIRTY GLSurfaceView.RENDERMODE_WHEN_DIRTY} +setting, as described in the next section.</p> + + +<h2 id="cont-render">Enable Continuous Rendering</h2> + +<p>If you have diligently followed along with the example code in this class to this point, make +sure you comment out the line that sets the render mode only draw when dirty, otherwise OpenGL +rotates the shape only one increment and then waits for a call to {@link +android.opengl.GLSurfaceView#requestRender requestRender()} from the {@link +android.opengl.GLSurfaceView} container:</p> + +<pre> +public MyGLSurfaceView(Context context) { + ... + // Render the view only when there is a change in the drawing data + //setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY); // comment out for auto-rotation +} +</pre> + +<p>Unless you have objects changing without any user interaction, it’s usually a good idea have this +flag turned on. Be ready to uncomment this code, because the next lesson makes this call applicable +once again.</p> |