Android OpenGL ES 應用(二) 紋理

 

要是做復雜的OpenGL應用程序，一定會用到紋理技術。紋理說白了就是把圖片或者視頻圖像繪制到OpenGL空間中。

因此紋理也有坐標系，稱ST坐標，或者UV

 

 

上面是紋理坐標空間，但沒有固定的方向

下面演示加載一張image作為紋理貼圖。

 

 

public class TextureUtils {

	public static int createTexture(InputStream ins) {
		int[] textures = new int[1];
		GLES20.glGenTextures(1, textures, 0);//生成一個紋理
		
		
		int textureId = textures[0];
		GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureId);
		GLES20.glTexParameterf(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER,GLES20.GL_NEAREST); 
		GLES20.glTexParameterf(GLES20.GL_TEXTURE_2D,GLES20.GL_TEXTURE_MAG_FILTER,GLES20.GL_LINEAR);
		GLES20.glTexParameterf(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_S,GLES20.GL_CLAMP_TO_EDGE);
		GLES20.glTexParameterf(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_T,GLES20.GL_CLAMP_TO_EDGE);
		//上面是紋理貼圖的取樣方式，包括拉伸方式，取臨近值和線性值
		Bitmap bitmap = BitmapFactory.decodeStream(ins);
		GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bitmap, 0);//讓圖片和紋理關聯起來，加載到OpenGl空間中
		Log.d(OPENGL,bitmap: + bitmap);
		bitmap.recycle();//不需要，可以釋放
		return textureId;
	}

}

 

 

 

 

public class MyRenderer implements Renderer {

	public static float[] projMatrix = new float[16];// 投影
	public static float[] viewMatrix = new float[16];// 相機
	public static float[] mViewPjMatrix;// 總變換矩陣
	public static float[] matrixs = new float[16];
	public static int textureId = -1;
	Context context;
	MyDrawModel drawModel;

	public MyRenderer(Context context) {
		this.context = context;
	}

	@Override
	public void onDrawFrame(GL10 arg0) {
		GLES20.glClear( GLES20.GL_DEPTH_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT);
		Log.e(, textureId: + textureId);
		drawModel.drawFrame(textureId);
	}

	@Override
	public void onSurfaceChanged(GL10 arg0, int w, int h) {
		GLES20.glViewport(0, 0, w, h);
		float ratio = (float) w / h;
		Matrix.frustumM(projMatrix, 0, -ratio, ratio, -1, 1, 1, 10);//投影矩陣設置
		Matrix.setLookAtM(viewMatrix, 0, 0, 0, 3, 0, 0, 0, 0.0f, 1.0f, 0.0f);//攝像機坐標設置
	}

	@Override
	public void onSurfaceCreated(GL10 g, EGLConfig eglConfig) {
		GLES20.glClearColor(0.5f,0.5f,0.5f, 1.0f);  
		GLES20.glEnable(GLES20.GL_DEPTH_TEST);
		InputStream ins = null;
		drawModel = new MyDrawModel();
		drawModel.init();
		try {
			ins = context.getAssets().open(house.jpg);
			textureId = TextureUtils.createTexture(ins);
			Log.e(, textureId: + textureId);
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				ins.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		GLES20.glDisable(GLES20.GL_CULL_FACE);
	}

}

 

public class MyDrawModel {

	private int programId;
	private int mVPMatrixHandle; // 總變換矩陣引用id
	private int positionHandle; // 頂點位置id
	private int texCoorHandle; // 頂點紋理坐標id

	private FloatBuffer vertexBuffer;
	private FloatBuffer texCoorBuffer;

	public MyDrawModel() {
	}

	public void init() {
		initData();
		int vertexsharder = GLHelper.compileScript(GLES20.GL_VERTEX_SHADER,
				GLScript.vertex2);
		int fragmentsharder = GLHelper.compileScript(GLES20.GL_FRAGMENT_SHADER,
				GLScript.fragment2);
		programId = GLHelper.linkAttach(vertexsharder, fragmentsharder);
		boolean isOK = GLHelper.checkProgram(programId);
		positionHandle = GLES20.glGetAttribLocation(programId, aPosition);
		texCoorHandle = GLES20.glGetAttribLocation(programId, aTexCoor);
		mVPMatrixHandle = GLES20.glGetUniformLocation(programId, uMVPMatrix);

		Log.d(OPENGL, positionHandle: + positionHandle + ;texCoorHandle:
				+ texCoorHandle + ;mVPMatrixHandle: + mVPMatrixHandle + ;
				+ isOK);
	}

	private void initData() {

		//X,Y,Z,繪畫的頂點
		float vertices[] = new float[] {
		           0,     0, 0,
			   -1.8f, -1f, 0,
			   1.8f, -1f, 0,
			   1.8f,  1f, 0,
			   -1.8f,  1f, 0,
			   -1.8f, -1f, 0
		   };

		ByteBuffer vb = ByteBuffer.allocateDirect(vertices.length * 4);
		vb.order(ByteOrder.nativeOrder());
		vertexBuffer = vb.asFloatBuffer();
		vertexBuffer.put(vertices);
		vertexBuffer.position(0);

		//紋理空間坐標 S,T
		float texCoor[] = new float[] { 
				0.5f, 0.5f,
				0f,     1f,
				1f,     1f,
				1f,     0f,
				0f,     0f,
				0f,     1f 
			};

		ByteBuffer cb = ByteBuffer.allocateDirect(texCoor.length * 4);
		cb.order(ByteOrder.nativeOrder());
		texCoorBuffer = cb.asFloatBuffer();
		texCoorBuffer.put(texCoor);
		texCoorBuffer.position(0);
	}

	public void drawFrame(int textureId) {
		
		 GLES20.glUseProgram(programId);
		 
		 // // 初始化矩陣
		 Matrix.setRotateM(MyRenderer.matrixs, 0, 0, 1, 0, 0);
		 Matrix.translateM(MyRenderer.matrixs, 0, 0, 0, 1);
		 
		 //矩陣轉換 ,投影矩陣，攝像機矩陣，模型矩陣
		 MyRenderer.mViewPjMatrix = new float[16];
		 Matrix.multiplyMM(MyRenderer.mViewPjMatrix, 0, MyRenderer.viewMatrix,0, MyRenderer.matrixs, 0);
		 Matrix.multiplyMM(MyRenderer.mViewPjMatrix, 0, MyRenderer.projMatrix,0, MyRenderer.mViewPjMatrix, 0);
		 GLES20.glUniformMatrix4fv(mVPMatrixHandle, 1, false, MyRenderer.mViewPjMatrix, 0);
		
		 GLES20.glVertexAttribPointer(positionHandle, 3, GLES20.GL_FLOAT, false, 3 * 4, vertexBuffer);
		 GLES20.glVertexAttribPointer(texCoorHandle,  2, GLES20.GL_FLOAT, false, 2 * 4, texCoorBuffer);
		
		 GLES20.glEnableVertexAttribArray(positionHandle);
		 GLES20.glEnableVertexAttribArray(texCoorHandle);
		
		 GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
		 GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureId);
		 GLES20.glDrawArrays(GLES20.GL_TRIANGLE_FAN, 0, 6);//六個定點，繪制三角形

	}

}

OpenGL需要把設備的坐標歸一化到[-1,-1]空間中，所以這裡涉及到矩陣相乘的理論，包括世界坐標，物體坐標，攝像機坐標的轉換，以後會詳細介紹。

 

public class GLScript {

	public GLScript() {
	}
	
	public static final String vertex1 = attribute vec4 mPosition;
 +  
            void main()
 +  
            {
 +  
                gl_Position=mPosition;
  +  
            }
;  
  
    public static final String fragment1 = precision mediump float;
 +  
            uniform vec4 mColor;
 +  
            void main(){ gl_FragColor=mColor;
};  
    
    public static final String vertex2 = uniform mat4 uMVPMatrix;

    		 + attribute vec3 aPosition;

    		 + attribute vec2 aTexCoor;

    		 + varying vec2 vTextureCoord;
 
    		 + void main() { 

    		 + gl_Position = uMVPMatrix * vec4(aPosition,1);

    		 + vTextureCoord = aTexCoor;
 
    		 + }

    		;
    
    public static final String fragment2 = precision mediump float;

    		+ varying vec2 vTextureCoord;

    		+ uniform sampler2D sTexture;

    		+ void main() { 

    		+ vec2 coord =  vTextureCoord;

    		+ coord.s =  coord.s * 0.5;
 //其實是去圖像的一半，向量縮小了
    		+ gl_FragColor = texture2D(sTexture, coord); 

    		+ }

    		;

}

 

 

coord.s =  coord.s * 0.5;

這樣是取紋理圖像的一半，顯示到界面上也就是圖片的前半部分內容

 

 

其它的工具類和上一篇文章一樣。

 

內容顯示

 

 

原圖：