Copying the backbuffer's image back to a texture

N

Nate Bross

Contributor
Joined
Apr 6, 2005
Location
Chicago, IL
If you are trying to take a screenshot, I nocked this class together to make it a bit easier; but it's not really necessary as it's just 1 line of code anyway.

Visual Basic: 
    Public Class ScreenShot
        Public dxDevice As Direct3D.Device     

        Public Sub New(ByVal Device As Direct3D.Device)
            dxDevice = Device
        End Sub

        Public Sub TakeScreenShot()
            TakeShot()
        End Sub

        Private Sub TakeShot()
            SurfaceLoader.Save("test.jpg", ImageFileFormat.Jpg, dxDevice.GetBackBuffer(0, 0, BackBufferType.Mono))
        End Sub
    End Class
 
E

EFileTahi-A

Contributor
Joined
Aug 8, 2004
Location
Portugal / Barreiro
Hi, tks for the posts Nate,

I'm just trying to retrieve (at some point) all that is rendered in the backbuffer as image because I need to scale its contents +50%, and then, drawn back the scaled image to the screen.

Code: 
Example:
[I](Pseucode)[/I]
You clear the screen (800x600) using black color;

[I]You draw the following into the back buffer[/I]
You draw a 300 pixel diameter circle;
You draw a 100x200 box;
And you draw 120x50 box;

[I]Now you retrieve all that is drawn so far and scale it by +50%[/I]
Texture = BackbufferContents;
ScaledImageTexture = Texture.Size +50%

You clear the screen again using black color
you draw the scaled image;

Continue drawing other graphics which are no needed to be scaled

If this is called screen shot, or some type of reflection, I really can't tell...

Just a question about the surfaceLoarder.Save, what kind of object is it? Can you add a line for me to see the way you declare it?
 
Last edited:
N

Nate Bross

Contributor
Joined
Apr 6, 2005
Location
Chicago, IL
SurfaceLoader is a built-in object into Direct3DX, see this for more information.

If you just want to get the BackBuffers contents you can use

Visual Basic: 
dxDevice.GetBackBuffer(0, 0, BackBufferType.Mono)

This returns a Direct3D.Surface object, not a texture, but it shouldn't be very difficult to convert it.

HTH
 
E

EFileTahi-A

Contributor
Joined
Aug 8, 2004
Location
Portugal / Barreiro
What If I asked you to drop me a line showing me how to get and convert the backbuffer into a texture? I would really apreciate that.

Netherthe less, thank you very much for your help so far. :)
 
Last edited:
N

Nate Bross

Contributor
Joined
Apr 6, 2005
Location
Chicago, IL
I haven't got a compiler here, but this should work.


Visual Basic: 
            Dim gs As GraphicsStream
            gs = SurfaceLoader.SaveToStream(ImageFileFormat.Bmp, dxDevice.GetBackBuffer(0, 0, BackBufferType.Mono))
            Dim bmp As New Bitmap(gs)
            Dim tx As New Texture(dxDevice, bmp, Usage.AutoGenerateMipMap, Pool.SystemMemory)
 
G

Goose

Newcomer
Joined
Feb 3, 2006
Multiple Pass Question

So I tried this and it worked great for accessing the texture in system memory from a single pass of a HLSL technique. My next question is: Is there a faster way to quickly get the texture back to the GPU so that the pixel shader in the second pass has access to it and can use it as int input? The SurfaceLoader.SaveToStream() is extremely slow since its writing the texture out to the system memory. It seems like there should be a faster way to do it without the intermediate texture going to the system memory and then back to the gpu. Thanks again
 
S

SteelRaiden

Newcomer
Joined
May 27, 2009
Nate Bross

YOU ARE THE BEST!!! This damn method drove me crazy...
The damn Movie.RenderToTexture method generates a texture and I searched for days how to save that texture in a bitmap... Someone says "use frontbuffer" yes but it is very slow... So "use textureloader.save" but is still slow... so "use surfaceloader.save" slow. Use that BackBuffer... FAST!! That what I need... take a bitmap from a video in a FAST way... thank you!!!
 
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