I am found a bug in my code, that cause mesh data corruption in certain situation using staging buffer. I have:
temporary mesh data
staging buffer with certain size, that used simultaneously by command buffer and memcpy, but not same segment at a time.
Buffer allocator, that gives part of suitable vertex-index buffer, where mesh data transfers from staging by vkCmdCopyBuffer. Buffer contains many of segments, given for different meshes.
The issue that when I am using staging buffer simultaneously by command buffer and memcpy, mesh data writes incorrectly (become overwritten/corrupted) and even badly can cause VK_ERROR_DEVICE_LOST .
https://i.sstatic.net/xluPf.jpg "correct mesh"
https://i.sstatic.net/aW949.jpg "broken mesh"
[[nodiscard]] static Result writeMeshBuffer(TransferData &data, GpuMesh &buffer)
{
Result result; using namespace vkw;
auto &mesh = buffer.source;
size_t vSize = mesh.vertices_count * mesh.vertex_size;
size_t iSize = mesh.indices_count * mesh.index_size;
size_t mesh_size = vSize + iSize;
auto &staging_offset = data.stagingData.buffer_offset_unused;
// write data to staging buffer
{
// guaranteed that mesh_size will less or equal than staging buffer size
//FIXME false condition generate broken meshes somehow
bool is_wait_before = mesh_size > TransferStagingData::BUFFER_SIZE - staging_offset;
//will work correctly:
//bool is_wait_before = true;
if (is_wait_before) // if we need more memory on staging buffer than not used already
{
result = data.wait_transfer();
if (result != VK_SUCCESS)
return result;
staging_offset = 0;
}
uint8_t *pMemory = static_cast<uint8_t*>(data.stagingData.pMemory) + staging_offset;
memcpy(pMemory, mesh.vertices.pX, vSize);
memcpy(pMemory + vSize, mesh.indices.pXX, iSize);
if (not is_wait_before)
{
result = data.wait_transfer();
if (result != VK_SUCCESS)
return result;
}
}
// write data from staging buffer to mesh buffer
{
auto cmd_cpy_buff = [](CommandBuffer cmd, BufferCopy copy, Offsets offsets, DeviceSizeT size)
{
cmd.cmd_copy_buffer(copy, offsets, size);
};
// SRC DST
BufferCopy copy = { data.stagingData.buffer, buffer.info.buffer };
Offsets offsets = { staging_offset, buffer.info.region.offset };
result = data.transfer.prepare(cmd_cpy_buff, data.transfer.cmd_buffer, copy, offsets, mesh_size);
if (result != VK_SUCCESS)
return result;
data.reset_fence();
result = data.transfer.submit({&data.transfer.cmd_buffer,1},{}, {}, {}, data.transferFence);
if (result != VK_SUCCESS)
return result;
}
// save usused offset to data.stagingData.buffer_offset_unused;
staging_offset = staging_offset == 0 ? mesh_size : 0;
return result;
}
If I can't use staging buffer like this, than why.
If i have an error, idk where.
