How do I properly update a vertex array in OpenGL Es 2.0?

Question

When I update my vertex array on iOS in OpenGL 2.0, the original vertex data is staying on the screen -- ie the 1st flush is persistent (the initial set of points I sent down to

Answer 1

For Android users out there, I just confirmed that it's possible to have deformable geometry using vertex attribute arrays in OpenGL ES 2.0 on Android, in a little test. The annoying thing is you don't get to pass a pointer to your own array, instead you have to use a FloatBuffer (or similar type). Sample code:

Initialization:

    // initialize vertex byte buffer for shape coordinates
    ByteBuffer bb = ByteBuffer.allocateDirect(
            // (number of coordinate values * 4 bytes per float)
            coords.length * 4);
    // use the device hardware's native byte order
    bb.order(ByteOrder.nativeOrder());

    // create a floating point buffer from the ByteBuffer
    vertexBuffer = bb.asFloatBuffer();
    // add the coordinates to the FloatBuffer
    vertexBuffer.put(coords);
    // set the buffer to read the first coordinate
    vertexBuffer.position(0);

Drawing Code:

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

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

    float newValue = (float) Math.sin((float) (frame++) / 1000) + 1;
    System.out.println(newValue);

    vertexBuffer.put(0, newValue);

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