OpenGL函数拒绝渲染三角形

Question

这可能与我的转变有关，但现在我无法弄清楚这一点，这让我发疯。我已经包装了绘制代码，以便我可以轻松定义新的三角形。但是，当我把它放到一个函数中时，它只是显示一个灰屏。功能代码如下：

 public void Draw(float[] mViewMatrix, float[] mModelMatrix, float[] mProjectionMatrix, int mPositionHandle,  int mColorHandle, int mMVPMatrixHandle)
{

    long time = SystemClock.uptimeMillis() % 10000L;
    float angleInDegrees = (360.0f / 10000.0f) * ((int) time);      

    Matrix.setIdentityM(mModelMatrix, 0);
    Matrix.rotateM(mModelMatrix, 0, angleInDegrees, 0.0f, 0.0f, 1.0f);     

    aBuffer = ByteBuffer.allocateDirect(verts.length * mBytesPerFloat)
    .order(ByteOrder.nativeOrder()).asFloatBuffer();



    //aBuffer.position(mPositionOffset);
    GLES20.glVertexAttribPointer(mPositionHandle, mPositionDataSize, GLES20.GL_FLOAT, false,
            mStrideBytes, aBuffer);        

    GLES20.glEnableVertexAttribArray(mPositionHandle);        

    // Pass in the color information
    aBuffer.position(mColorOffset);
    GLES20.glVertexAttribPointer(mColorHandle, mColorDataSize, GLES20.GL_FLOAT, false,
            mStrideBytes, aBuffer);        

    GLES20.glEnableVertexAttribArray(mColorHandle);

    // This multiplies the view matrix by the model matrix, and stores the result in the MVP matrix
    // (which currently contains model * view).
    Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0);

    // This multiplies the modelview matrix by the projection matrix, and stores the result in the MVP matrix
    // (which now contains model * view * projection).
    Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0);

    GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mMVPMatrix, 0);
    GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, 3); 
}

正在运行的代码是：

        public void onDrawFrame(GL10 glUnused) 
{
    GLES20.glClear(GLES20.GL_DEPTH_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT);                    



    // Do a complete rotation every 10 seconds.
    long time = SystemClock.uptimeMillis() % 10000L;
    float angleInDegrees = (360.0f / 10000.0f) * ((int) time);

    // Draw the triangle facing straight on.
    Matrix.setIdentityM(mModelMatrix, 0);
    Matrix.rotateM(mModelMatrix, 0, angleInDegrees, 0.0f, 0.0f, 1.0f);        
    drawTriangle(mTriangle1Vertices);

    // Draw one translated a bit down and rotated to be flat on the ground.
    Matrix.setIdentityM(mModelMatrix, 0);
    Matrix.translateM(mModelMatrix, 0, 0.0f, -1.0f, 0.0f);
    Matrix.rotateM(mModelMatrix, 0, 90.0f, 1.0f, 0.0f, 0.0f);
    Matrix.rotateM(mModelMatrix, 0, angleInDegrees, 0.0f, 0.0f, 1.0f);        
    drawTriangle(mTriangle2Vertices);

    // Draw one translated a bit to the right and rotated to be facing to the left.
    Matrix.setIdentityM(mModelMatrix, 0);
    Matrix.translateM(mModelMatrix, 0, 1.0f, 0.0f, 0.0f);
    Matrix.rotateM(mModelMatrix, 0, 90.0f, 0.0f, 1.0f, 0.0f);
    Matrix.rotateM(mModelMatrix, 0, angleInDegrees, 0.0f, 0.0f, 1.0f);
    drawTriangle(mTriangle3Vertices);
    */

    /*
    for (int x = 0; x < staticHolder.objectList.size(); x++)
    {
        staticHolder.objectList.get(x).Draw(mViewMatrix, mModelMatrix, mProjectionMatrix, mPositionHandle, mColorHandle, mMVPMatrixHandle);
    }
    */
}   

/**
 * Draws a triangle from the given vertex data.
 * 
 * @param aTriangleBuffer The buffer containing the vertex data.
 */
private void drawTriangle(final FloatBuffer aTriangleBuffer)
{       
    // Pass in the position information
    aTriangleBuffer.position(mPositionOffset);
    GLES20.glVertexAttribPointer(mPositionHandle, mPositionDataSize, GLES20.GL_FLOAT, false,
            mStrideBytes, aTriangleBuffer);        

    GLES20.glEnableVertexAttribArray(mPositionHandle);        

    // Pass in the color information
    aTriangleBuffer.position(mColorOffset);
    GLES20.glVertexAttribPointer(mColorHandle, mColorDataSize, GLES20.GL_FLOAT, false,
            mStrideBytes, aTriangleBuffer);        

    GLES20.glEnableVertexAttribArray(mColorHandle);

    // This multiplies the view matrix by the model matrix, and stores the result in the MVP matrix
    // (which currently contains model * view).
    Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0);

    // This multiplies the modelview matrix by the projection matrix, and stores the result in the MVP matrix
    // (which now contains model * view * projection).
    Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0);

    GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mMVPMatrix, 0);
    GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, 3);                               
}

我传入相同的变量，这里使用的最终变量初始化相同。封装函数中还有一些其他工作。知道为什么它拒绝在函数中渲染吗？

以下代码加载列表中的对象：

  final float[] triangle1VerticesData = {
            // X, Y, Z, 
            // R, G, B, A
            -0.5f, -0.25f, 0.0f, 
            1.0f, 0.0f, 0.0f, 1.0f,

            0.5f, -0.25f, 0.0f,
            0.0f, 0.0f, 1.0f, 1.0f,

            0.0f, 0.559016994f, 0.0f, 
            0.0f, 1.0f, 0.0f, 1.0f};

    final float[] triangle2VerticesData = {
            // X, Y, Z, 
            // R, G, B, A
            -0.5f, -0.25f, 0.0f, 
            1.0f, 1.0f, 0.0f, 1.0f,

            0.5f, -0.25f, 0.0f, 
            0.0f, 1.0f, 1.0f, 1.0f,

            0.0f, 0.559016994f, 0.0f, 
            1.0f, 0.0f, 1.0f, 1.0f};

    // This triangle is white, gray, and black.
    final float[] triangle3VerticesData = {
            // X, Y, Z, 
            // R, G, B, A
            -0.5f, -0.25f, 0.0f, 
            1.0f, 1.0f, 1.0f, 1.0f,

            0.5f, -0.25f, 0.0f, 
            0.5f, 0.5f, 0.5f, 1.0f,

            0.0f, 0.559016994f, 0.0f, 
            0.0f, 0.0f, 0.0f, 1.0f};

    staticHolder.objectList.add(new Triangle(triangle1VerticesData));
    staticHolder.objectList.add(new Triangle(triangle2VerticesData));
    staticHolder.objectList.add(new Triangle(triangle3VerticesData));

接收类是：

    public class Triangle extends shape 
    {

     public Triangle(float[] data)
     {
          verts = data;
     }

     }

Answer 1

在以下代码之后：

aBuffer = ByteBuffer.allocateDirect(verts.length * mBytesPerFloat).order(ByteOrder.nativeOrder()).asFloatBuffer();

您必须将顶点放入缓冲区（否则，它是空白的！）：

aBuffer.put(verts);

这不是在代码中起作用的原因是因为这三组顶点的缓冲区是预先分配的，然后顶点被放入其中（在初始化时）。它们每次都只是简单地传递给方法，因此不必再次输入put()。

关于这一点，您需要避免在 Draw 方法中进行分配，因为它每帧调用多次，可能会导致渲染缓慢。分配一次aBuffer，每次都放入新的顶点。