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[OpenGL ES] VBO 顶点缓冲对象

互联网 diligentman 6天前 5次浏览

VBO: Vertex Buffer object   顶点缓冲对象

为什么要用VBO?

不使用VBO时,每次绘制( glDrawArrays )图形时都是从本地内存处获取顶点数据然后传输给OpenGL来绘制,这样就会频繁的操作CPU->GPU增大开销,从而降低效率。使用VBO,可以把顶点数据缓存到GPU开辟的一段内存中,然后使用时不必再从本地获取,而是直接从显存中获取,这样就能提升绘制的效率。


创建VBO 

1、创建VBO
GLES20.glGenBuffers(1, vbos, 0);

2、绑定VBO
GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, vbos[0]);

3、分配VBO需要的缓存大小
GLES20.glBufferData(GLES20.GL_ARRAY_BUFFER, vertex.length * 4,null, GLES20. GL_STATIC_DRAW);

4、为VBO设置顶点数据的值
GLES20.glBufferSubData(GLES20.GL_ARRAY_BUFFER, 0, vertexData.length * 4, vertexBuffer);

5、解绑VBO
GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, 0);


使用VBO

1、绑定VBO
GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, vbos[0]);

2、设置顶点数据
GLES20.glVertexAttribPointer(vPosition, 2, GLES20.GL_FLOAT, false, 8, 0);

3、解绑VBO
GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, 0);


GGLTextureRender    VBO的使用
package com.example.opengldemo;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.opengl.GLES20;
import android.opengl.GLUtils;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;

public class GGLTextureRender implements MyGLSurfaceView.MyGLRender {

    private Context context;
    //顶点坐标
    private final float[] vertexData = {
            -1f, -1f,
            1f, -1f,
            -1f, 1f,
            1f, 1f
    };

    //纹理坐标
    private final float[] fragmentData = {
            0f, 1f,
            1f, 1f,
            0f, 0f,
            1f, 0f
    };

    private FloatBuffer vertexBuffer;
    private FloatBuffer fragmentBuffer;

    public GGLTextureRender(Context context) {
        this.context = context;

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

        fragmentBuffer = ByteBuffer.allocateDirect(fragmentData.length * 4)
                .order(ByteOrder.nativeOrder())
                .asFloatBuffer()
                .put(fragmentData);
        fragmentBuffer.position(0);
    }

    private int program;

    private int vPosition;
    private int fPosition;

    private int textureid;
    private int sampler;

    private int vboId;

    @Override
    public void onSufaceCreated() {
        String vertexSource = GShaderUtil.getRawResource(context, R.raw.vertex_shader);
        String fragmentSource = GShaderUtil.getRawResource(context, R.raw.fragment_shader);
        program = GShaderUtil.createProgram(vertexSource, fragmentSource);

        if (program > 0) {
            //顶点坐标
            vPosition = GLES20.glGetAttribLocation(program, "v_Position");
            //纹理坐标
            fPosition = GLES20.glGetAttribLocation(program, "f_Position");

            sampler = GLES20.glGetUniformLocation(program,"sTexture");

            /**********************创建VBO-START************************************************/
            int [] vbos = new int[1];
            GLES20.glGenBuffers(1, vbos, 0);
            vboId = vbos[0];
            //绑定
            GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, vboId);
            //分配内存
            GLES20.glBufferData(GLES20.GL_ARRAY_BUFFER, vertexData.length*4 + fragmentData.length*4,
                    null,GLES20. GL_STATIC_DRAW);
            //缓存到显存
            GLES20.glBufferSubData(GLES20.GL_ARRAY_BUFFER, 0, vertexData.length * 4, vertexBuffer);
            GLES20.glBufferSubData(GLES20.GL_ARRAY_BUFFER, vertexData.length * 4, fragmentData.length*4,
                    fragmentBuffer);
            //解绑
            GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, 0);
           /******************************VBO-END***********************************************/

            int[] textureIds = new int[1];
            GLES20.glGenTextures(1, textureIds, 0);
            textureid = textureIds[0];


            GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureid);
            GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
            GLES20.glUniform1i(sampler, 0);

            //设置环绕过滤方法
            GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_S, GLES20.GL_REPEAT);
            GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_T, GLES20.GL_REPEAT);

            GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_LINEAR);
            GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_LINEAR);

            Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(), R.drawable.androids);
            if (bitmap == null) {
                return;
            }
            GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bitmap, 0);
            //回收
            bitmap.recycle();
            bitmap = null;

            //解绑
            GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, 0);
        }
    }

    @Override
    public void onSufaceChanged(int width, int height) {
        GLES20.glViewport(0,0,width,height);
    }

    @Override
    public void onDrawFrame() {
        //清屏
        GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
        //使用颜色清屏
        GLES20.glClearColor(1.0f, 0.0f, 0.0f, 1.0f);

        //使用program
        GLES20.glUseProgram(program);

        //绑定
        GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureid);

        /**********************VBO-START************************************************/
        //绑定VBO
        GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, vboId);
        /**********************VBO-END************************************************/

        //使用顶点坐标
        GLES20.glEnableVertexAttribArray(vPosition);
        /**********************VBO-START************************************************/
        //传0 从VBO中取值
        GLES20.glVertexAttribPointer(vPosition, 2, GLES20.GL_FLOAT, false, 8, 0);
        /**********************VBO-END************************************************/

        GLES20.glEnableVertexAttribArray(fPosition);

        /**********************VBO-START************************************************/
        //VBO
        GLES20.glVertexAttribPointer(fPosition, 2, GLES20.GL_FLOAT, false, 8,
                vertexData.length * 4);
        /**********************VBO-END************************************************/

        GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);
        //解绑
        GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, 0);

        /**********************VBO-START************************************************/
        //解绑VBO
        GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, 0);
        /**********************VBO-END************************************************/
    }
}

 


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