如何完全取消绑定GL_ELEMENT_ARRAY_BUFFER？ [英] How to fully unbind a GL_ELEMENT_ARRAY_BUFFER?
问题描述
我正在研究一个多线程应用程序，它可以同时将几何图形渲染到多个FBO。我遇到了泄漏（如此问题所述）。
我已经能够缩小一点 - 如果我做了一个改变，它会停止泄漏 - 但我不明白为什么。
开每一个线程（每个线程都有自己的共享上下文），我在做每个渲染周期的下列代码：
//上传
positionBuffer = getUnusedArrayBufferFromPool（）;
glBindBuffer（GL_ARRAY_BUFFER，positionBuffer）;
glBufferData（GL_ARRAY_BUFFER，sizeof（float）* 4 * vertexCount，positions，GL_STREAM_DRAW）;
{
GLuint vertexArray;
glGenVertexArrays（1，& vertexArray）;
glBindVertexArray（vertexArray）;
elementBuffer = getUnusedElementArrayBufferFromPool（）;
glBindBuffer（GL_ELEMENT_ARRAY_BUFFER，elementBuffer）;
glBufferData（GL_ELEMENT_ARRAY_BUFFER，sizeof（unsigned int）* elementCount，elements，GL_STREAM_DRAW）;
glBindVertexArray（0）;
glDeleteVertexArrays（1，& vertexArray）;
}
glBindBuffer（GL_ELEMENT_ARRAY_BUFFER，0）;
glBindBuffer（GL_ARRAY_BUFFER，0）;
//渲染（可能位于不同的上下文中）
GLuint vertexArray;
glGenVertexArrays（1，& vertexArray）;
glBindVertexArray（vertexArray）;
glUseProgram（programName）;
{
GLint positionAttribute = glGetAttribLocation（programName，position）;
glBindBuffer（GL_ARRAY_BUFFER，positionBuffer）;
glVertexAttribPointer（（GLuint）positionAttribute，4 / * XYZW * /，GL_FLOAT，GL_FALSE，sizeof（float）* 4，（void *）0）;
glEnableVertexAttribArray（（GLuint）positionAttribute）;
{
glBindBuffer（GL_ELEMENT_ARRAY_BUFFER，elementBuffer）;
glDrawElements（GL_TRIANGLES，（GLsizei）elementCount，GL_UNSIGNED_INT，（void *）0）;
glBindBuffer（GL_ELEMENT_ARRAY_BUFFER，0）;
}
glDisableVertexAttribArray（（GLuint）positionAttribute）;
glBindBuffer（GL_ARRAY_BUFFER，0）;
}
glUseProgram（0）;
glBindVertexArray（0）;
glDeleteVertexArrays（1，& vertexArray）;
//清理（可能位于不同的上下文中）
glBindBuffer（GL_ARRAY_BUFFER，positionBuffer）;
glBufferData（GL_ARRAY_BUFFER，0，0，GL_STREAM_DRAW）;
glBindBuffer（GL_ARRAY_BUFFER，0）;
throwArrayBufferBackInPool（positionBuffer）;
// glBindBuffer（GL_ELEMENT_ARRAY_BUFFER，elementBuffer）;
// glBufferData（GL_ELEMENT_ARRAY_BUFFER，0，0，GL_STREAM_DRAW）;
// glBindBuffer（GL_ELEMENT_ARRAY_BUFFER，0）;
// throwElementArrayBufferBackInPool（elementBuffer）; //为什么如果我们回收它会泄漏？
glDeleteBuffers（1，& elementBuffer）;
如果我交换最后2行 - 如果我将元素缓冲区放回池中而不是删除它每个渲染周期 - OpenGL驱动监视器表明一个巨大的泄漏。
但我更喜欢将它集中，因为调用 glDeleteBuffers（） code>每一帧都很慢。
我错过了什么？我假设我无法从某些东西中解除 elementBuffer 的作用，并且某些东西持续引用它，导致泄漏 - 但我无法弄清楚是什么。
编辑：刚刚在另一个系统上测试过（Mac OS 10.6）如果我回收任何缓冲区，它就会泄漏。
$ b 编辑：我修改了我的应用程序，使 GL_ARRAY_BUFFER 与 GL_ELEMENT_ARRAY_BUFFER 分开汇集，因此 elementBuffer 始终与 GL_ELEMENT_ARRAY_BUFFER 。但如果我 throwElementArrayBufferBackInPool（elementBuffer）; 。
编辑：，它仍然会泄漏。澄清为什么我要在上传和渲染过程中创建和删除VAO - 因为它们可能发生在不同的共享GL上下文中，并且VAO无法在上下文之间共享。
编辑：我修改了我的应用程序，以便在将缓冲区重新放入缓冲池之前提供零大小的缓冲区数据，但仍然很快就会泄漏。 缓冲池用于绑定 GL_ARRAY_BUFFER 以及GL_ELEMENT_ARRAY_BUFFER对象。更糟的是，你首先使用 elementBuffer 来绑定 GL_ARRAY_BUFFER ，但是继续使用 GL_ELEMENT_ARRAY_BUFFER 。我还没有完全包围它，但是在混合名称空间和不一致的绑定使用之间，我会把钱放在那里。
我的建议是：为 GL_ELEMENT_ARRAY_BUFFER 使用创建一个独立的缓冲区名称池，并确保您始终如一地使用它。
I'm working on a multithreaded app that simultaneously renders geometry to multiple FBOs. I'm experiencing a leak (as described on this question).
I've been able to narrow it down a little — if I make one change, it stops leaking — but I can't figure out why.
On each of 4 threads (each with its own shared context), I'm doing the following each render cycle:
// Upload
positionBuffer = getUnusedArrayBufferFromPool();
glBindBuffer(GL_ARRAY_BUFFER, positionBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(float)*4*vertexCount, positions, GL_STREAM_DRAW);
{
GLuint vertexArray;
glGenVertexArrays(1, &vertexArray);
glBindVertexArray(vertexArray);
elementBuffer = getUnusedElementArrayBufferFromPool();
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementBuffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(unsigned int)*elementCount, elements, GL_STREAM_DRAW);
glBindVertexArray(0);
glDeleteVertexArrays(1, &vertexArray);
}
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
// Render (possibly on a different context)
GLuint vertexArray;
glGenVertexArrays(1, &vertexArray);
glBindVertexArray(vertexArray);
glUseProgram(programName);
{
GLint positionAttribute = glGetAttribLocation(programName, "position");
glBindBuffer(GL_ARRAY_BUFFER, positionBuffer);
glVertexAttribPointer((GLuint)positionAttribute, 4 /* XYZW */, GL_FLOAT, GL_FALSE, sizeof(float)*4, (void*)0);
glEnableVertexAttribArray((GLuint)positionAttribute);
{
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementBuffer);
glDrawElements(GL_TRIANGLES, (GLsizei)elementCount, GL_UNSIGNED_INT, (void*)0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
}
glDisableVertexAttribArray((GLuint)positionAttribute);
glBindBuffer(GL_ARRAY_BUFFER, 0);
}
glUseProgram(0);
glBindVertexArray(0);
glDeleteVertexArrays(1, &vertexArray);
// Cleanup (possibly on a different context)
glBindBuffer(GL_ARRAY_BUFFER, positionBuffer);
glBufferData(GL_ARRAY_BUFFER, 0, 0, GL_STREAM_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, 0);
throwArrayBufferBackInPool(positionBuffer);
//glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementBuffer);
//glBufferData(GL_ELEMENT_ARRAY_BUFFER, 0, 0, GL_STREAM_DRAW);
//glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
//throwElementArrayBufferBackInPool(elementBuffer); // Why does this leak if we recycle it?
glDeleteBuffers(1, &elementBuffer);
If I swap the last 2 lines — if I throw the element buffer back into the pool instead of deleting it each render cycle — OpenGL Driver Monitor indicates a huge leak.
But I'd prefer to pool it, since calling glDeleteBuffers() each frame is really slow.
What am I missing? I assume I'm failing to unbind elementBuffer from something — and that something is holding on to a reference to it, causing the leak — but I can't figure out what.
Edit: Just tested on a different system (Mac OS 10.6) — on that system, it leaks if I recycle any buffers.
Edit: I modified my application so that GL_ARRAY_BUFFER is pooled separately from GL_ELEMENT_ARRAY_BUFFER, and so that elementBuffer is consistently bound to GL_ELEMENT_ARRAY_BUFFER. But it still leaks if I throwElementArrayBufferBackInPool(elementBuffer);.
Edit: Clarified why I'm creating and deleting a VAO during Upload and during Rendering — because they might happen on different shared GL contexts, and VAOs can't be shared between contexts.
Edit: I modified my application to provide zero-size buffer data before throwing the buffers back into the pool, but it still leaks just as quickly.
Your buffer pool is used for binding GL_ARRAY_BUFFER as well as GL_ELEMENT_ARRAY_BUFFER objects. Worse, you're first using elementBuffer for binding a GL_ARRAY_BUFFER, but then carry on using it for an GL_ELEMENT_ARRAY_BUFFER. I haven't fully wrapped my head around it, but somewhere between mixing the namespaces and the inconsistent use of bindings I'd put my money on that.
My suggestion: Create a separate pool of buffer names for GL_ELEMENT_ARRAY_BUFFER use and make sure you're using it consistently for only that.
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