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brettm

OpenGL Is it possible to create Vertex Buffers in DX9 that are not "lockable" [kb940105]

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brettm    100
Hi all, I work for a programming team that visualizes large amounts of scientific data in 3D. We currently render using DirectX 9.0c (programmed through SlimDX API), and support XP, Vista (both 32/64 bit). We have a problem, in that we are very pressed for virtual address space in the process. A significant pressure on virtual address space are vertex buffers. Our application carefully tracks rendering resources that have been created, and maintains a cache of resources that have been used, and may be required again (for instance, as the user is navigating the scene, certain tiles may be come visible, or not). As far as we are concerned, there is no need for the rendering resources to be resident in system RAM; because if we require rendering resources for a tile that doesn't currently exist, we page the relevant data in from disk and rebuild the resource. The same happens for "Device Lost". We create a lot of vertex buffers and index buffers, in the "default" pool. The documentation reads as if these resources will only be resident in video memory, but it seems that due to Vista VM virtualization, this is not the case; and it seems that all of our resources consume virtual address space. This causes problems for us on 32-bit systems (virtual memory exhaustion). I have read the Microsoft KB940105 article here: http://support.microsoft.com/default.aspx/kb/940105 This indicates that I will be able to solve my problem, if I don't make my rendering resources "Lockable". However, "Lockable" is DX10 terminology; is it possible to create non-lockable resources in DX9? I have written a test program to allocate vertex buffers in various configurations, and used SysInternals "VMMap" to see where DirectX makes VM allocations corresponding to my resources. For vertex buffers (on Vista) for instance: Pool.Managed - allocates in Unmanaged Heap Pool.Default, Usage.None - allocates in "Private" Pool.Default, Usage.WriteOnly - allocates in "Private" ("Private" means "memory allocated by VirtualAlloc and not suballocated either by the Heap Manager or the .NET run time"). So to reiterate my question; is it possible to create vertex buffers that don't consume virtual address space, on Vista, using DX9? The project is large and porting to OpenGL is not really an option. Porting to DX10 is feasible, but we aren't ready to abandon XP support, just yet. Best regards Brett

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andur    781
I don't think its possible in dx9. How would you get your vertex data into a dx9 vertex buffer without locking it?

The only reason it works in dx10, is that you can supply the vertex data at the same time as creating the buffer.

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brettm    100
Thanks andur,

my concern is that you are right. However, the knowledge base article that I referred to does specifically state that it applies to DX9:
Quote:

If an application creates its own in-memory copy of its video resources, or the application uses DirectX 9 or an earlier version, the virtual address space contains the WDDM video memory manager's virtualized range and the application's copy. Applications that use graphics APIs that are earlier than DirectX 10 and that target GPUs that have large amounts of video memory can easily exhaust their virtual address space.

To address this problem, Microsoft is changing the way that the video memory manager maintains the content of video memory resources. This change is being made so that a permanent virtual address range does not have to be used for each virtualized allocation. With the new approach, only allocations that are created as "lockable" consume space in the virtual address space of the application. Allocations that are not created as "lockable" do not consume space. This approach significantly reduces the virtual address space that is used. Therefore, the application can run on large video memory configurations without reaching the limits.


This strikes me as very odd; in that it claims to fix a problem in DX9 for resources so long as resources are not "lockable", if it then turns out that it's not possible to create resources that are not "lockable"!

Perhaps the article would make more sense if they were referring only to "Textures" rather than "video resources"; since it is possible to populate those with data without ever locking them (either by rendering into them, or using "UpdateTexture" to populate from a temporary SystemMemory texture)? Does anyone have any more light to shed?

Regards
Brett

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AdamGL    130
From that quote you just offered, it seems like Microsoft fixed this issue in Direct3D APIs higher than Direct3D 9. So it looks like you are out of luck as far as DX9 goes.

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Flimflam    665
As AdamGL stated, it appears they're referring to technology after DirectX9 while using limitations in DirectX9 as a comparison to how things are changing onward.

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