[英]Unable to get opengl ES to draw anything in 2D on Android
這是我為了使2D繪圖起作用而編寫的代碼。 活動,視圖和渲染器設置正確。 我得到一個全黑的屏幕,但上面沒有多邊形。 什么也沒畫。 這將使我發瘋...
public class OpenGLActivity extends Activity {
private GLSurfaceView surfaceView;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(
WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN
);
this.surfaceView = new OpenGLSurfaceView(this);
setContentView(this.surfaceView);
}
@Override
protected void onPause() {
super.onPause();
surfaceView.onPause();
}
@Override
protected void onResume() {
super.onResume();
surfaceView.onResume();
}
}
public class OpenGLSurfaceView extends GLSurfaceView {
private OpenGLSurfaceRenderer renderer;
public OpenGLSurfaceView(Context context) {
super(context);
this.renderer = new OpenGLSurfaceRenderer();
setRenderer(renderer);
}
}
public class OpenGLSurfaceRenderer implements Renderer {
private FloatBuffer vertexBuffer;
private float[] vertices = {
0.0f, 1.0f, 0.0f,
0.0f, 0.0f, 0.0f,
1.0f, 1.0f, 0.0f,
1.0f, 0.0f, 0.0f,
0.0f, 10.0f, 0.0f,
0.0f, 0.0f, 0.0f,
10.0f, 10.0f, 0.0f,
10.0f, 0.0f, 0.0f
};
public OpenGLSurfaceRenderer() {
ByteBuffer byteBuffer = ByteBuffer.allocateDirect(vertices.length * (Float.SIZE >> 3));
vertexBuffer = byteBuffer.asFloatBuffer();
vertexBuffer.put(vertices);
vertexBuffer.position(0);
}
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_FASTEST);
gl.glClearColor(0.0f, 0.0f, 0.0f, 1);
gl.glShadeModel(GL10.GL_FLAT);
gl.glDisable(GL10.GL_DEPTH_TEST);
gl.glEnable(GL10.GL_TEXTURE_2D);
gl.glDisable(GL10.GL_DITHER);
gl.glDisable(GL10.GL_LIGHTING);
gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
}
public void onDrawFrame(GL10 gl) {
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
gl.glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
gl.glTranslatef(0.0f, 0.0f, 0.5f);
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, 4);
}
public void onSurfaceChanged(GL10 gl, int width, int height) {
gl.glViewport(0, 0, width, height);
// Clear the projection matrix
gl.glMatrixMode(GL10.GL_PROJECTION);
gl.glLoadIdentity();
// Set up orthographic projection mode (2D drawing)
gl.glOrthof(0, width, height, 0, 0, 1);
gl.glMatrixMode(GL10.GL_MODELVIEW);
gl.glLoadIdentity();
}
}
我看到四個問題:
glDrawArrays()的最后一個參數應該是8,而不是4。這是您提供的頂點數,而不是三角形帶中的三角形數。
正射投影使您的世界單位等於像素。 您的前4個頂點描述的是1像素寬的三角形。 也許屏幕的左下角有一個白色像素?
您每幀都沿Z軸推進模型投影。 2幀后,它將顯示在視錐范圍之外。
最重要的是,您沒有在ByteBuffer上設置正確的順序。 將此行插入您的OpenGlRenderer()構造函數中:
公共OpenGLSurfaceRenderer(){ByteBuffer byteBuffer = ByteBuffer.allocateDirect(vertices.length * 4); byteBuffer.order(ByteOrder.nativeOrder()); <------ vertexBuffer = byteBuffer.asFloatBuffer(); vertexBuffer.put(vertices); vertexBuffer.position(0); }
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