动态更改顶点缓冲区数据opengl

Question

我有一个使用缓冲区绘制点的点类。我希望能够改变正在绘制的内容（用新点数更新场景）。重新创建一个全新的对象听起来不太好，所以我一直在尝试改变缓冲区的内容。最近我发现约glBufferSubData()，但我不知道如何使用它。

这是我的观点类：

public class Point { 
    private int mProgram, mPositionHandle, mColorHandle, mMVPMatrixHandle; 
    private FloatBuffer vertexBuffer,colorBuffer; 
    private static final int COORDS_PER_VERTEX = 3; 
    private static final int COORDS_PER_COLOR = 3; 
    private int vertexCount,colorCount; 


    private final String vertexShaderCode = 
      "uniform mat4 uMVPMatrix;" + 
        "attribute vec4 vPosition;" + 
        "attribute mediump vec4 vColor;" + 
        "varying mediump vec4 vaColor;" + 
        "void main() {" + 
        " vaColor = vColor;" + 
        " gl_Position = uMVPMatrix * vPosition;" + 
        " gl_PointSize = 20.0;" + 
        "}"; 

    private final String fragmentShaderCode = 
      "precision mediump float;" + 
        "varying mediump vec4 vaColor;" + 
        "void main() {" + 
        " gl_FragColor = vaColor;" + 
        "}"; 


    private static int vertexStride = COORDS_PER_VERTEX * 4; 
    private final int colorStride = COORDS_PER_COLOR * 4; 


    public Point(float pointCoords[],float colorCoords[]){ 
     this.vertexCount = pointCoords.length/COORDS_PER_VERTEX; 
     this.colorCount = colorCoords.length/COORDS_PER_COLOR; 

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



     ByteBuffer cbb = ByteBuffer.allocateDirect(colorCoords.length * 4); 
     cbb.order(ByteOrder.nativeOrder()); 
     colorBuffer = cbb.asFloatBuffer(); 
     colorBuffer.put(colorCoords); 
     colorBuffer.position(0); 


     int vertexShader = MyGLRenderer.loadShader(GLES20.GL_VERTEX_SHADER, 
       vertexShaderCode); 
     int fragmentShader = MyGLRenderer.loadShader(GLES20.GL_FRAGMENT_SHADER, 
       fragmentShaderCode); 

     // create empty OpenGL ES Program 
     mProgram = GLES20.glCreateProgram(); 

     // create empty OpenGL ES Program 
     mProgram = GLES20.glCreateProgram(); 

     // add the vertex shader to program 
     GLES20.glAttachShader(mProgram, vertexShader); 

     // add the fragment shader to program 
     GLES20.glAttachShader(mProgram, fragmentShader); 

     // creates OpenGL ES program executables 
     GLES20.glLinkProgram(mProgram); 
    } 

    public void draw(float[] mvpMatrix) { 
     // Add program to OpenGL ES environment 
     GLES20.glUseProgram(mProgram); 

     // get handle to vertex shader's vPosition member 
     mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition"); 

     // Enable a handle to the triangle vertices 
     GLES20.glEnableVertexAttribArray(mPositionHandle); 

     // Prepare the point coordinate data 
     GLES20.glVertexAttribPointer(mPositionHandle, COORDS_PER_VERTEX, 
       GLES20.GL_FLOAT, false, 
       vertexStride, vertexBuffer); 


     mColorHandle = GLES20.glGetAttribLocation(mProgram,"vColor"); 

     GLES20.glEnableVertexAttribArray(mColorHandle); 
     // Set color for drawing the triangle 
     GLES20.glVertexAttribPointer(mColorHandle, COORDS_PER_COLOR, GLES20.GL_FLOAT, false, 
       colorStride, colorBuffer); 

     // get handle to shape's transformation matrix 
     mMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix"); 

     //TRANSLATION 
     float[] transMatrix = new float[16]; 

     Matrix.setIdentityM(transMatrix,0); 
     Matrix.translateM(transMatrix,0,0.5f,0,0); 
     Matrix.multiplyMM(transMatrix,0,mvpMatrix,0,transMatrix,0); 


     // Apply the projection and view transformation 
     GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mvpMatrix, 0); 

     GLES20.glDrawArrays(GLES20.GL_POINTS, 0, vertexCount); 

     // Disable vertex array 
     GLES20.glDisableVertexAttribArray(mPositionHandle); 
    } 

    /** 
    * Change content of buffer 
    */ 
    public void changeBufferData(float[] newBufferInfo) { 
     GLES20.glBufferSubData(?,0,newBufferInfo.length*4,vertexBuffer); 
    } 

    } 

Answer 1

您目前使用客户端顶点数组使用glVertexAttribPointer每绘图上传的数据。动态更新它不会比你已经做的更昂贵，因为你已经不得不为每次绘制操作分配和复制数据到驱动程序拥有的内存中。

但是，正如你所说的，再造的缓冲区是昂贵，因此避免了客户端顶点上传强烈建议......

你缺少的部分是需要建立一个顶点缓冲区对象（glGenBuffers等） ，然后您可以使用它来代替客户端属性。 glBufferData和glSubBufferData用于修补其中一个缓冲对象的内容。