Locks a range of vertex data and obtains a pointer to the vertex buffer memory.
HRESULT Lock( [in] UINT OffsetToLock, [in] UINT SizeToLock, [out] VOID **ppbData, [in] DWORD Flags );
- OffsetToLock [in]
Offset into the vertex data to lock, in bytes. To lock the entire vertex buffer, specify 0 for both parameters, SizeToLock and OffsetToLock.
- SizeToLock [in]
Size of the vertex data to lock, in bytes. To lock the entire vertex buffer, specify 0 for both parameters, SizeToLock and OffsetToLock.
- ppbData [out]
VOID* pointer to a memory buffer containing the returned vertex data.
- Flags [in]
Combination of zero or more locking flags that describe the type of lock to perform. For this method, the valid flags are:
For a description of the flags, see D3DLOCK.
If the method succeeds, the return value is D3D_OK. If the method fails, the return value can be D3DERR_INVALIDCALL.
As a general rule, do not hold a lock across more than one frame. When working with vertex buffers, you are allowed to make multiple lock calls; however, you must ensure that the number of lock calls match the number of unlock calls. DrawPrimitive calls will not succeed with any outstanding lock count on any currently set vertex buffer.
The D3DLOCK_DISCARD and D3DLOCK_NOOVERWRITE flags are valid only on buffers created with D3DUSAGE_DYNAMIC.
For information about using D3DLOCK_DISCARD or D3DLOCK_NOOVERWRITE with IDirect3DVertexBuffer9::Lock, see Using Dynamic Vertex and Index Buffers.