Question

我需要用新的顶点更新网格。我这样创建VBO（最初创建时只有一个顶点）：

public Mesh(float[] vertex, int size)
{
    texture = null;
    meshType = 1;           //will draw lines

    FloatBuffer verticesBuffer = null;
    IntBuffer indicesBuffer = null;
    int vboID;

    try
    {
        vertexCount = size;

        vaoID = glGenVertexArrays();
        glBindVertexArray(vaoID);

        vboIDList = new ArrayList<>();

        // Vertices VBO generation
        vboID = glGenBuffers();
        vboIDList.add(vboID);
        verticesBuffer = MemoryUtil.memAllocFloat(size * 3);        // !!! Must Be manually freed!
        verticesBuffer.put(vertex).flip();
        glBindBuffer(GL_ARRAY_BUFFER, vboID);
        glBufferData(GL_ARRAY_BUFFER, verticesBuffer, GL_STATIC_DRAW);
        glVertexAttribPointer(0, 3, GL_FLOAT, false, 0, 0);
        vertexAttrArrCount += 1;

        // Indices VBO generation
        vboID = glGenBuffers();
        vboIDList.add(vboID);
        indicesBuffer = MemoryUtil.memAllocInt(size);             // !!! Must be manually freed!
        indicesBuffer.put(new int[]{0}).flip();
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboID);
        glBufferData(GL_ELEMENT_ARRAY_BUFFER, indicesBuffer, GL_STATIC_DRAW);

        // unbinding
        glBindBuffer(GL_ARRAY_BUFFER, 0);
        glBindVertexArray(0);
    }
    finally
    {
        if (verticesBuffer != null)
        {
            MemoryUtil.memFree(verticesBuffer);                             // Freeing vertex buffer
        }

        if (indicesBuffer != null)
        {
            MemoryUtil.memFree(indicesBuffer);                              // Freeing indices buffer
        }
    }

}

然后我要更新VBO缓冲区并将新的顶点写入其中。请注意，我确实创建了VBO，以为新顶点留有足够的空间，并且控制了它不会被过度填充。我还控制了每个渲染调用绘制的元素数量，因此不会绘制空的0/0/0顶点。

我的问题是，此代码有效：

public void updateVBO(float[] vertices, int[] indices, int size)
{
    if (meshType == 1)
    {
        lineCount = size;

        FloatBuffer subDataF = null;
        IntBuffer subDataI = null;
        int vboID;

        try
        {
            //System.out.printf("Adding vertex (%f, %f, %f) to position %d\n",vertex.x,vertex.y,vertex.z,position);
            vboID = vboIDList.get(0);
            //float[] vert = new float[]{vertex.x, vertex.y, vertex.z};
            subDataF = MemoryUtil.memAllocFloat(vertices.length);        // !!! Must Be manually freed!
            subDataF.put(vertices).flip();
            glBindBuffer(GL_ARRAY_BUFFER, vboID);
            glBufferData(GL_ARRAY_BUFFER, subDataF, GL_STATIC_DRAW);
            glVertexAttribPointer(0, 3, GL_FLOAT, false, 0, 0);

            vboID = vboIDList.get(1);
            //int[] index = new int[]{ position };
            subDataI = MemoryUtil.memAllocInt(indices.length);        // !!! Must Be manually freed!
            subDataI.put(indices).flip();
            glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboID);
            glBufferData(GL_ELEMENT_ARRAY_BUFFER, subDataI, GL_STATIC_DRAW);

            //glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
        }
        finally
        {
            if (subDataF != null)
            {
                MemoryUtil.memFree(subDataF);
            }
            if (subDataI != null)
            {
                MemoryUtil.memFree(subDataI);
            }
        }
    }
}

因此，当我传递整个顶点数组并从头开始重新分配VBO内存时，它恰好绘制了我所需的内容。但是我想使用glBufferSubData，这样我每次添加新顶点时都不会重新分配内存。这段代码不起作用：

public void addVertex(Vector3f vertex, int position)
{
    if (meshType == 1)
    {
        FloatBuffer subDataF = null;
        IntBuffer subDataI = null;
        int vboID;

        lineCount = position+1;

        try
        {
            System.out.printf("Adding vertex (%f, %f, %f) to position %d\n",vertex.x,vertex.y,vertex.z,position);
            vboID = vboIDList.get(0);
            float[] vert = new float[]{vertex.x, vertex.y, vertex.z};
            subDataF = MemoryUtil.memAllocFloat(3);        // !!! Must Be manually freed!
            subDataF.put(vert).flip();
            glBindBuffer(GL_ARRAY_BUFFER, vboID);
            glBufferSubData(GL_ARRAY_BUFFER, position * 3 * 4, subDataF);
            glVertexAttribPointer(0, 3, GL_FLOAT, false, 0, 0);

            vboID = vboIDList.get(1);
            int[] index = new int[]{ position };
            subDataI = MemoryUtil.memAllocInt(1);        // !!! Must Be manually freed!
            subDataI.put(index).flip();
            glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboID);
            glBufferSubData(GL_ELEMENT_ARRAY_BUFFER, position * 4, subDataI);

            glBindBuffer(GL_ARRAY_BUFFER, 0);
            glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
        }
        finally
        {
            if (subDataF != null)
            {
                MemoryUtil.memFree(subDataF);
            }
            if (subDataI != null)
            {
                MemoryUtil.memFree(subDataI);
            }
        }
    }
}

我也知道它没有优化创建floatbuffer和intbuffer的方式，我只是想在清理之前使其工作。我正在尝试很多事情，因此，最后一段代码很奇怪。

还是，我不明白我在做什么错。我确实检查了我是否正确传递了所有数据，并且似乎计算了位置（和偏移量）的大小。它只是什么也没画，而当我使用glBufferData时却画了。

有人可以解释我在哪里犯错吗？

经过所有建议，这就是我的最终目的，但是它仍然根本不起作用：

public void addVertex(Vector3f vertex, int position)
{
    if (meshType == 1)
    {
        FloatBuffer subDataF = null;
        IntBuffer subDataI = null;
        int vboID;

        lineCount = position+1;

        try
        {
            System.out.printf("Adding vertex (%f, %f, %f) to position %d\n",vertex.x,vertex.y,vertex.z,position);
            vboID = vboIDList.get(0);
            float[] vert = new float[]{vertex.x, vertex.y, vertex.z};
            subDataF = MemoryUtil.memAllocFloat(3);        // !!! Must Be manually freed!
            subDataF.put(vert).flip();
            glBindBuffer(GL_ARRAY_BUFFER, vboID);
            glBufferSubData(GL_ARRAY_BUFFER, (long)(position * 3 * 4), (FloatBuffer)subDataF);
            glVertexAttribPointer(0, 3, GL_FLOAT, false, 0, 0);

            vboID = vboIDList.get(1);
            int[] index = new int[]{ position };
            subDataI = MemoryUtil.memAllocInt(1);        // !!! Must Be manually freed!
            subDataI.put(index).flip();

            glBindVertexArray(vaoID);
            glBufferSubData(GL_ELEMENT_ARRAY_BUFFER, (long)(position * 4), (IntBuffer)subDataI);
        }
        finally
        {
            if (subDataF != null)
            {
                MemoryUtil.memFree(subDataF);
            }
            if (subDataI != null)
            {
                MemoryUtil.memFree(subDataI);
            }
        }
    }
}

我确实检查了VAO ID是否正确。

Answer 1

就像我想的那样，这很愚蠢，根本与VAO绑定无关。

问题是，当我最初创建VBO时，我是这样做的：

// Vertices VBO generation
        vboID = glGenBuffers();
        vboIDList.add(vboID);
        verticesBuffer = MemoryUtil.memAllocFloat(size * 3);        // !!! Must Be manually freed!
        verticesBuffer.put(vertex).flip();
        glBindBuffer(GL_ARRAY_BUFFER, vboID);
        glBufferData(GL_ARRAY_BUFFER, verticesBuffer, GL_STATIC_DRAW);
        glVertexAttribPointer(0, 3, GL_FLOAT, false, 0, 0);
        vertexAttrArrCount += 1;

我假设因为我为size * 3浮点数分配了缓冲区，所以它将具有该大小，并且当我将其放入VBO中时，它将分配size * 3 * 4字节，即足以容纳size * 3浮点数。

结果不对！因为我只将一个顶点（3个浮点数）放入缓冲区-它只会分配该数量的空间。因此，当我稍后尝试使用glBufferSubData时-GPU上仅可容纳3个浮点的空间，自然不会将值放在需要的地方。实际上，我感到惊讶的是它并没有完全崩溃。

要解决此问题，此刻我改为这样做：

// Vertices VBO generation
        ...
        verticesBuffer.put(vertex).put(new float[size*3 - 3]).flip();
        ...

所以基本上我是手动将一个空数组放入FloatBuffer中，以确保缓冲区大小正确。

结果如下：构造函数：

public Mesh(float[] vertex, int size)
{
    texture = null;
    meshType = 1;           //will draw lines

    FloatBuffer verticesBuffer = null;
    IntBuffer indicesBuffer = null;
    int vboID;

    try
    {
        vertexCount = size;

        vaoID = glGenVertexArrays();
        glBindVertexArray(vaoID);

        vboIDList = new ArrayList<>();

        // Vertices VBO generation
        vboID = glGenBuffers();
        vboIDList.add(vboID);
        verticesBuffer = MemoryUtil.memAllocFloat(size * 3);        // !!! Must Be manually freed!
        verticesBuffer.put(vertex).put(new float[size*3 - 3]).flip();
        glBindBuffer(GL_ARRAY_BUFFER, vboID);
        glBufferData(GL_ARRAY_BUFFER, verticesBuffer, GL_STATIC_DRAW);
        glVertexAttribPointer(0, 3, GL_FLOAT, false, 0, 0);
        vertexAttrArrCount += 1;

        // Indices VBO generation
        vboID = glGenBuffers();
        vboIDList.add(vboID);
        indicesBuffer = MemoryUtil.memAllocInt(size);             // !!! Must be manually freed!
        indicesBuffer.put(new int[size]).flip();                  // I need the first element 0 anyway
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboID);
        glBufferData(GL_ELEMENT_ARRAY_BUFFER, indicesBuffer, GL_STATIC_DRAW);

        // unbinding
        glBindBuffer(GL_ARRAY_BUFFER, 0);
        glBindVertexArray(0);
    }
    finally
    {
        if (verticesBuffer != null)
        {
            MemoryUtil.memFree(verticesBuffer);                             // Freeing vertex buffer
        }

        if (indicesBuffer != null)
        {
            MemoryUtil.memFree(indicesBuffer);                              // Freeing indices buffer
        }
    }

}

然后更新：

public void addVertex(Vector3f vertex, int position)
{
    if (meshType == 1)
    {
        FloatBuffer subDataF = null;
        IntBuffer subDataI = null;
        int vboID;

        lineCount = position+1;

        try
        {
            vboID = vboIDList.get(0);
            float[] vert = new float[]{vertex.x, vertex.y, vertex.z};
            subDataF = MemoryUtil.memAllocFloat(vert.length);        // !!! Must Be manually freed!
            subDataF.put(vert).flip();
            glBindBuffer(GL_ARRAY_BUFFER, vboID);
            glBufferSubData(GL_ARRAY_BUFFER, (long)(position * 3 * 4), (FloatBuffer)subDataF);
            glVertexAttribPointer(0, 3, GL_FLOAT, false, 0, 0);

            vboID = vboIDList.get(1);
            int[] index = new int[]{ position };
            subDataI = MemoryUtil.memAllocInt(index.length);        // !!! Must Be manually freed!
            subDataI.put(index).flip();
            glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboID);
            glBufferSubData(GL_ELEMENT_ARRAY_BUFFER, (long)(position * 4), (IntBuffer)subDataI);

            glBindBuffer(GL_ARRAY_BUFFER, 0);
            glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
        }
        finally
        {
            if (subDataF != null)
            {
                MemoryUtil.memFree(subDataF);
            }
            if (subDataI != null)
            {
                MemoryUtil.memFree(subDataI);
            }
        }
    }
}

它有效。请注意，该代码有点脏，我在发布答案之前没有对其进行清理。

OpenGL glBufferSubData-无法正常运行

1 个答案: