5 replies to this topic

[rtclawson]

In SlimDX for Direct3D 9, the Texture class has a method called LockRectangle. This method does not exist in the Texture2D class in SlimDX.Direct3D11. How do you achieve the same functionality, namely, getting a DataRectangle object out of a Texture2D object, such that it can be used for reading and writing?

 

Thank you!

[Mike.Popoloski]

You use the Map / Unmap methods on the DeviceContext.

[rtclawson]

Awesome. I see now, thanks. My next issue is this. I want to lock a Texture for writing, so I make this call,

 

DataBox b = _device.ImmediateContext.MapSubresource(_texture, 0, 0, MapMode.Write, MapFlags.None);

 

which looks like it should work. However, I get an INVALIDARGS error. I assume the problem is that the texture I pass in does not have the right flags set. So, I have tried several permutations of the BindFlags, CpuAccessFlags, and Usage enums. Unfortunately, the only settings that I have been able to find that will even create the Texture2D object without an INVALIDARGS error is when they are all set to None, or Default.

 

My question is, what flags should be set on the texture to enable it to be mapped for writing?

[Mike.Popoloski]

It depends what you're trying to do with the texture. If you're just trying to update the texture (ie. write to it from the CPU), you have two options:

 

1. If you're updating only once or very rarely (not every frame), create with Usage.Default and CpuAccessFlags.None. Then, you can use the DeviceContext.UpdateSubresource() method to write a whole new set of texture data into the resource.

 

2. If you're updating the resource often, create with Usage.Dynamic and CpuAccessFlags.Write. Then, you can use the Map / Unmap commands to write changes into the texture memory.

 

In both of those cases, you probably want BindFlags.ShaderResource, since presumably you're rendering with this texture from a shader. If, however, you want to *read* back from a texture that the GPU has written to, such as the backbuffer, things get more complicated. You need to do the following:

• Create a "staging" texture by using Usage.Staging and CpuAccessFlags.Read (and possible Write as well).
• Use the DeviceContext.CopySubresource method to copy from the desired texture to read (such as the backbuffer texture) into your staging texture
• Once there, you can map the staging texture and read/write to it. You can probably CopySubresource back into the original resource at that point too if you want.

[rtclawson]

I decided to configure the texture using option 2. The following gives me an INVALIDARGS error in the Texture2D constructor. Could it be that I have not configured the device correctly?

 

Texture2DDescription description = new Texture2DDescription

{

ArraySize = 1,

Format = _format,

Width = _width,

Height = _height,

OptionFlags = ResourceOptionFlags.None,

Usage = ResourceUsage.Dynamic,

BindFlags = BindFlags.ShaderResource,

CpuAccessFlags = CpuAccessFlags.Write,

SampleDescription = new SlimDX.DXGI.SampleDescription(1, 0),

MipLevels = _levelCount,

};

_texture = new SlimDX.Direct3D11.Texture2D(_device, description);

 

Here is the device creation code:

 

Device device;

SlimDX.DXGI.SwapChainDescription swapDesc = new SlimDX.DXGI.SwapChainDescription

{

BufferCount = 1,

Flags = SlimDX.DXGI.SwapChainFlags.AllowModeSwitch,

IsWindowed = true,

ModeDescription = new SlimDX.DXGI.ModeDescription(0, 0, new SlimDX.Rational(60, 1), SlimDX.DXGI.Format.R8G8B8A8_UNorm),

OutputHandle = handle,

SampleDescription = new SlimDX.DXGI.SampleDescription(1, 0),

SwapEffect = SlimDX.DXGI.SwapEffect.Discard,

Usage = SlimDX.DXGI.Usage.RenderTargetOutput

};

　

 

Device.CreateWithSwapChain(DriverType.Hardware, DeviceCreationFlags.Debug, swapDesc, out device, out _swapChain);

 

I am new to this stuff. The answer may be obvious.

[Mike.Popoloski]

Nothing seems obviously wrong. Are you checking the debug output to see if there are any messages from the D3D debug runtimes?