OpenGL ES(5) - 添加动作

绘制对象在屏幕上是OpenGL最基本的功能，不过你也可以使用Canvas和Drawable对象实现。OpenGL ES提供额外的能力来让你在三维空间中移动和转换绘制对象，提供用户体验。

旋转一个形状

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为了旋转形状，你需要创建另外一个转换矩阵，然后合并到投影和摄像视图转换矩阵中：

<span class="kwd" style="color: rgb(0, 0, 136);">private</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">float</span><span class="pun" style="color: rgb(102, 102, 0);">[]</span><span class="pln" style="color: rgb(0, 0, 0);"> mRotationMatrix </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">new</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">float</span><span class="pun" style="color: rgb(102, 102, 0);">[</span><span class="lit" style="color: rgb(0, 102, 102);">16</span><span class="pun" style="color: rgb(102, 102, 0);">];</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">public</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">void</span><span class="pln" style="color: rgb(0, 0, 0);"> onDrawFrame</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">GL10 gl</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
    </span><span class="pun" style="color: rgb(102, 102, 0);">...</span><span class="pln" style="color: rgb(0, 0, 0);">
    </span><span class="com" style="color: rgb(136, 0, 0);">// Create a rotation transformation for the triangle</span><span class="pln" style="color: rgb(0, 0, 0);">
    </span><span class="kwd" style="color: rgb(0, 0, 136);">long</span><span class="pln" style="color: rgb(0, 0, 0);"> time </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">SystemClock</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">uptimeMillis</span><span class="pun" style="color: rgb(102, 102, 0);">()</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">%</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">4000L</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
    </span><span class="kwd" style="color: rgb(0, 0, 136);">float</span><span class="pln" style="color: rgb(0, 0, 0);"> angle </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">0.090f</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">((</span><span class="kwd" style="color: rgb(0, 0, 136);">int</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> time</span><span class="pun" style="color: rgb(102, 102, 0);">);</span><span class="pln" style="color: rgb(0, 0, 0);">
    </span><span class="typ" style="color: rgb(102, 0, 102);">Matrix</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">setRotateM</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">mRotationMatrix</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">0</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> mAngle</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">0</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">0</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="lit" style="color: rgb(0, 102, 102);">1.0f</span><span class="pun" style="color: rgb(102, 102, 0);">);</span><span class="pln" style="color: rgb(0, 0, 0);">

    </span><span class="com" style="color: rgb(136, 0, 0);">// Combine the rotation matrix with the projection and camera view</span><span class="pln" style="color: rgb(0, 0, 0);">
    </span><span class="typ" style="color: rgb(102, 0, 102);">Matrix</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">multiplyMM</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">mMVPMatrix</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">0</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> mRotationMatrix</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">0</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> mMVPMatrix</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">0</span><span class="pun" style="color: rgb(102, 102, 0);">);</span><span class="pln" style="color: rgb(0, 0, 0);">

    </span><span class="com" style="color: rgb(136, 0, 0);">// Draw triangle</span><span class="pln" style="color: rgb(0, 0, 0);">
    mTriangle</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">draw</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">mMVPMatrix</span><span class="pun" style="color: rgb(102, 102, 0);">);</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span>

开启持续渲染

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如果你跟随教程做的练习，那么你要确保注释掉了下面的语句，不然的话旋转时只有一个增量，然后等待requestRender()的调用：

<span class="kwd" style="color: rgb(0, 0, 136);">public</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">MyGLSurfaceView</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="typ" style="color: rgb(102, 0, 102);">Context</span><span class="pln" style="color: rgb(0, 0, 0);"> context</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
    </span><span class="pun" style="color: rgb(102, 102, 0);">...</span><span class="pln" style="color: rgb(0, 0, 0);">
    </span><span class="com" style="color: rgb(136, 0, 0);">// Render the view only when there is a change in the drawing data</span><span class="pln" style="color: rgb(0, 0, 0);">
    </span><span class="com" style="color: rgb(136, 0, 0);">//setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY); // comment out for auto-rotation</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span>