Android OpenGL ES 应用(二) 纹理

上一篇讲了基础入门 OpenGL (一) ，这一次主要学习OpenGL 纹理基本学习总结

要是做复杂的OpenGL应用程序，一定会用到纹理技术。纹理说白了就是把图片或者视频图像绘制到OpenGL空间中。

因此纹理也有坐标系，称ST坐标。或者UV

上面是纹理坐标空间。但没有固定的方向

以下演示载入一张image作为纹理贴图。

public class TextureUtils {

	public static int createTexture(InputStream ins) {
		int[] textures = new int[1];
		GLES20.glGenTextures(1, textures, 0);//生成一个纹理

		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);
		//上面是纹理贴图的取样方式，包含拉伸方式，取临近值和线性值
		Bitmap bitmap = BitmapFactory.decodeStream(ins);
		GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bitmap, 0);//让图片和纹理关联起来。载入到OpenGl空间中
		Log.d("OPENGL","bitmap:" + bitmap);
		bitmap.recycle();//不须要。能够释放
		return textureId;
	}

}

public class MyRenderer implements Renderer {

	public static float[] projMatrix = new float[16];// 投影
	public static float[] viewMatrix = new float[16];// 相机
	public static float[] mViewPjMatrix;// 总变换矩阵
	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);//投影矩阵设置
		Matrix.setLookAtM(viewMatrix, 0, 0, 0, 3, 0, 0, 0, 0.0f, 1.0f, 0.0f);//摄像机坐标设置
	}

	@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; // 总变换矩阵引用id
	private int positionHandle; // 顶点位置id
	private int texCoorHandle; // 顶点纹理坐标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,绘画的顶点
		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);

		//纹理空间坐标 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);

		 // // 初始化矩阵
		 Matrix.setRotateM(MyRenderer.matrixs, 0, 0, 1, 0, 0);
		 Matrix.translateM(MyRenderer.matrixs, 0, 0, 0, 1);

		 //矩阵转换 ,投影矩阵，摄像机矩阵。模型矩阵
		 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);//六个定点，绘制三角形

	}

}

OpenGL须要把设备的坐标归一化到[-1,-1]空间中。所以这里涉及到矩阵相乘的理论，包含世界坐标，物体坐标，摄像机坐标的转换。以后会具体介绍。

public class GLScript {

	public GLScript() {
	}

	public static final String vertex1 = "attribute vec4 mPosition;\n" +
            "void main()\n" +
            "{\n" +
                "gl_Position=mPosition;\n " +
            "}\n";  

    public static final String fragment1 = "precision mediump float;\n" +
            "uniform vec4 mColor;\n" +
            "void main(){ gl_FragColor=mColor;\n}";  

    public static final String vertex2 = "uniform mat4 uMVPMatrix;\n"
    		 + "attribute vec3 aPosition;\n"
    		 + "attribute vec2 aTexCoor;\n"
    		 + "varying vec2 vTextureCoord;\n"
    		 + "void main() { \n"
    		 + "gl_Position = uMVPMatrix * vec4(aPosition,1);\n"
    		 + "vTextureCoord = aTexCoor;\n"
    		 + "}\n"
    		;

    public static final String fragment2 = "precision mediump float;\n"
    		+ "varying vec2 vTextureCoord;\n"
    		+ "uniform sampler2D sTexture;\n"
    		+ "void main() { \n"
    		+ "vec2 coord =  vTextureCoord;\n"
    		+ "coord.s =  coord.s * 0.5;\n" //事实上是去图像的一半，向量缩小了
    		+ "gl_FragColor = texture2D(sTexture, coord); \n"
    		+ "}\n"
    		;

}

coord.s =  coord.s * 0.5;

这样是取纹理图像的一半，显示到界面上也就是图片的前半部分内容

其他的工具类和上一篇文章一样。

内容显示

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原图：

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