Android OpenGL學習筆記(一)

大家好，今天我講一下Android OpenGL，這個系列是我的學習筆記，希望對大家有所幫助！這一節將給大家簡潔的介紹一下術語，以及第一個Android OpenGL程序.

首先讓我看們看一下術語:

Vertex (頂點)
A vertex is a point in 3D space and is the building block for many objects. In OpenGL you can specify as few as two coordinates (X,Y) and as many as four (X,Y,Z,W). The w-axis is optional, the default value is set to 1.0. The z-axis is also optional, the default value is set to 0. In this series, we will use the three main coordinates X, Y, and Z, since the W is generally used as a placeholder. The plural of vertex is vertices (mainly important for non native speakers, because it may create confusion). All objects are drawn using vertices as their points, so a point will refer to a vertex.

Triangle (三角)
A triangle requires three points to be created. So in OpenGL, we use three vertices to create one.

Polygon (多邊形)
A polygon is an object which has at least three connected points. Therefor a triangle is also a polygon.

Primitives (基本實體)
A primitive is a three-dimensional object created using either triangles or polygons. A bit ironic: A detailed model with 50.000 vertices is also a primitive like a low detailed model with 500 vertices.

下面就是我們的第一個Android OpenGL程序:

package com.android.tutor;  
import android.app.Activity;  
import android.opengl.GLSurfaceView;  
import android.os.Bundle;  
public class OpenGl_Lesson1 extends Activity {  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
          
        GLSurfaceView mGlSurfaceView = new GLSurfaceView(this);  
          
         
        mGlSurfaceView.setRenderer(new OpenGLRender());  
        setContentView(mGlSurfaceView);  
          
    }  
} 

我們這裡的View是用的GLSurfaceView,但是它要setRenderer()一下，就像我們Activity裡面的setContentView()方法一樣!

這裡的OpenGLRender是我重新寫的類，它繼承於GLSurfaceView.Renderer,我們要實現其種的三個方法:

onSurfaceCreated(),onSurfaceChanged(),onDrawFrame()。代碼如下:

package com.android.tutor;  
import javax.microedition.khronos.egl.EGLConfig;  
import javax.microedition.khronos.opengles.GL10;  
import android.opengl.GLSurfaceView.Renderer;  
public class OpenGLRender implements Renderer {  
    @Override 
    public void onSurfaceCreated(GL10 gl, EGLConfig config) {  
        // TODO Auto-generated method stub  
          
        gl.glClearColor(0.9f, 0.2f, 0.2f, 1.0f);  
        gl.glClear(GL10.GL_COLOR_BUFFER_BIT);  
    }  
    @Override 
    public void onSurfaceChanged(GL10 gl, int width, int height) {  
        gl.glViewport(0, 0, width, height);  
    }  
    @Override 
    public void onDrawFrame(GL10 gl) {  
        // TODO Auto-generated method stub  
    }  
      
}  

 第10行就是相當於我們設置畫布顏色RGBA(紅綠藍透)，第11行這裡是清除深度顏色緩存，不加上一句，第10句不起作用，整個View的顏色

還是黑黑的！

運行效果如下: