Android OpenGL教程 二 2D形狀畫畫
阿新 • • 發佈：2018-01-31
glm osi ret vertex depth 1.0 inter 開始 wrap 首先畫個三角形
private float[] mTriangleArray={
0.0f,1.0f,0.0f,
1.0f,-1.0f,0.0f,
-1.0f,-1.0f,0.0f
};gl.glDrawArrays(GL10.GL_TRIANGLES, 0, mTriangleArray.length/3);
然後畫個兩個三角形拼成一個正方形，把之前的坐標換一下就好了
private float[] mTriangleArray={ 1.0f,1.0f,0.0f, 1.0f,-1.0f,0.0f, -1.0f,-1.0f,0.0f, -1.0f,-1.0f,0.0f, -1.0f,1.0f,0.0f, 1.0f,1.0f,0.0f };
看來glDrawArrays是三個三個坐標來畫的
我現在使用glDrawElements這個函數來畫正方形，這函數不僅可以畫多方形，而且還可以畫3D
private float[] mTriangleArray={ 1.0f,1.0f,0.0f, 1.0f,-1.0f,0.0f, -1.0f,-1.0f,0.0f, -1.0f,1.0f,0.0f }; private float[] mColor ={ 1.0f,0.0f,0.0f,1.0f, 1.0f,0.0f,0.0f,1.0f, 1.0f,0.0f,0.0f,1.0f, 1.0f,0.0f,0.0f,1.0f }; private byte[] cubeFacets = new byte[]{ 0, 1, 2, 0, 2, 3 }; gl.glVertexPointer(3, GL10.GL_FLOAT, 0, mTriangleBuffer); gl.glColorPointer(4, GL10.GL_FLOAT, 0, mColorBuffer); gl.glDrawElements(GL10.GL_TRIANGLE_STRIP , cubeFacetsBuffer.remaining(), GL10.GL_UNSIGNED_BYTE, cubeFacetsBuffer);
這函數的意思是你傳他畫三個點的坐標組的位置（第一個從0開始，一個坐標組有三個float），比如這個cubeFacets就是說0、1、2三個坐標連起來畫個三角形，然後0、2、3坐標畫個三角形。
以下是完整代碼
public class MainActivity extends Activity {
private GLSurfaceView mGLView;
public void onCreate(Bundle savedInstanceState){ super.onCreate(savedInstanceState); mGLView = new GLSurfaceView(this); //這裏使用的是自定義的GLSurfaceView的子類 mGLView.setRenderer(new GLRenderer()); setContentView(mGLView); } public void onPause(){ super.onPause(); mGLView.onPause(); } public void onResume(){ super.onResume(); mGLView.onResume(); } public class GLRenderer implements GLSurfaceView.Renderer { private float[] mTriangleArray={ 1.0f,1.0f,0.0f, 1.0f,-1.0f,0.0f, -1.0f,-1.0f,0.0f, -1.0f,1.0f,0.0f }; private float[] mColor ={ 1.0f,0.0f,0.0f,1.0f, 1.0f,0.0f,0.0f,1.0f, 1.0f,0.0f,0.0f,1.0f, 1.0f,0.0f,0.0f,1.0f }; private byte[] cubeFacets = new byte[]{ 0, 1, 2, 0, 2, 3 }; private FloatBuffer mTriangleBuffer; private FloatBuffer mColorBuffer; ByteBuffer cubeFacetsBuffer; public GLRenderer() { mTriangleBuffer = floatBufferUtil(mTriangleArray); mColorBuffer = floatBufferUtil(mColor); cubeFacetsBuffer = ByteBuffer.wrap(cubeFacets); } @Override public void onDrawFrame(GL10 gl) { // 清除屏幕和深度緩存 gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); // 設置當前矩陣模式為模型視圖。 gl.glMatrixMode(GL10.GL_MODELVIEW); // 允許設置頂點 //GL10.GL_VERTEX_ARRAY頂點數組 gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); // 允許設置顏色 //GL10.GL_COLOR_ARRAY顏色數組 gl.glEnableClientState(GL10.GL_COLOR_ARRAY); // 重置當前的模型觀察矩陣 gl.glLoadIdentity(); //將三角形在z軸上移動 gl.glTranslatef(0f, 0.0f, -2.0f); // 設置三角形 gl.glVertexPointer(3, GL10.GL_FLOAT, 0, mTriangleBuffer); // 設置三角形顏色 gl.glColorPointer(4, GL10.GL_FLOAT, 0, mColorBuffer); // 繪制三角形 gl.glDrawElements(GL10.GL_TRIANGLE_STRIP , cubeFacetsBuffer.remaining(), GL10.GL_UNSIGNED_BYTE, cubeFacetsBuffer); // 取消顏色設置 gl.glDisableClientState(GL10.GL_COLOR_ARRAY); // 取消頂點設置 gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); //繪制結束 gl.glFinish(); } @Override public void onSurfaceChanged(GL10 gl, int width, int height) { float ratio = (float) width / height; // 設置OpenGL場景的大小,(0,0)表示窗口內部視口的左下角，(w,h)指定了視口的大小 gl.glViewport(0, 0, width, height); // 設置投影矩陣 gl.glMatrixMode(GL10.GL_PROJECTION); // 重置投影矩陣 gl.glLoadIdentity(); // 設置視口的大小 gl.glFrustumf(-ratio, ratio, -1, 1, 1, 10); //以下兩句聲明，以後所有的變換都是針對模型(即我們繪制的圖形) gl.glMatrixMode(GL10.GL_MODELVIEW); gl.glLoadIdentity(); } @Override public void onSurfaceCreated(GL10 gl, EGLConfig config) { // 設置白色為清屏 gl.glClearColor(1, 1, 1, 1); } } // 定義一個工具方法，將float[]數組轉換為OpenGL ES所需的FloatBuffer private FloatBuffer floatBufferUtil(float[] arr) { FloatBuffer mBuffer; // 初始化ByteBuffer，長度為arr數組的長度*4，因為一個int占4個字節 ByteBuffer qbb = ByteBuffer.allocateDirect(arr.length * 4); // 數組排列用nativeOrder qbb.order(ByteOrder.nativeOrder()); mBuffer = qbb.asFloatBuffer(); mBuffer.put(arr); mBuffer.position(0); return mBuffer; }
}
Android OpenGL教程 二 2D形狀畫畫