動態更改頂點緩衝區數據opengl

Question

我有一個使用緩衝區繪製點的點類。我希望能夠改變正在繪製的內容（用新點數更新場景）。重新創建一個全新的對象聽起來不太好，所以我一直在嘗試改變緩衝區的內容。最近我發現約glBufferSubData()，但我不知道如何使用它。

這是我的觀點類：

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

您目前使用客戶端頂點數組使用glVertexAttribPointer每繪圖上傳的數據。動態更新它不會比你已經做的更昂貴，因爲你已經不得不爲每次繪製操作分配和複製數據到驅動程序擁有的內存中。

但是，正如你所說的，再造的緩衝區是昂貴，因此避免了客戶端頂點上傳強烈建議......

你缺少的部分是需要建立一個頂點緩衝區對象（glGenBuffers等） ，然後您可以使用它來代替客戶端屬性。 glBufferData和glSubBufferData用於修補其中一個緩衝對象的內容。