Copy backbuffer to a rendertarget

is there a real quick way to copy the back buffer to a rendertarget? i’m wanting to do a screen capture snap shot that i can then manipulate?
Thanks in advance

If you’re using a recent build of MG (later than October 15th), you can use GraphicsDevice.GetBackBufferData to get the backbuffer contents and then set them on a texture/RT using SetData. I don’t think it’s the fastest way to do it, but it’s the best you can do with the MG API. Make sure the surface format of the back buffer and the texture are the same (but that should be fine if you’re using the defaults).

is that really faster than just rendering it into RT?

No, it’s very much slower. But the question was how to copy from the backbuffer to a RT.

Thanks, Jjagg, exactly what i wanted, before this i could see no method of transferring the backbuffer to an RT, if i’m wrong please show me how, remember copying FROM the back buffer not to it

I think what Ravendarke means (and Jjagg of course knows :slight_smile: ) is that you’d be better off drawing all your screen (your scene) to a full-screen render-target anyways. Then, as a last step, you’d draw that to the backbuffer.
And before that you could use it to save it (screenshot) or draw it to another RT in order to manipulate it further.

If you have post-process effects then you’ll have to renter your scene to a RT anyway.
That’s the way I (and the others) would prefer to go.
Whereas if you’re doing a screenshot-util or something like that, that’s not critical in terms of performance, so no harm done…
Just my 2 cents.

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getting
Severity Code Description Project File Line Suppression State
Error CS1061 ‘GraphicsDevice’ does not contain a definition for ‘GetBackBufferData’ and no extension method ‘GetBackBufferData’ accepting a first argument of type ‘GraphicsDevice’ could be found (are you missing a using directive or an assembly reference?) Pick and Pile.Windows D:\MyProjects\MONOGAME\Projects\Pick and Pile\Pick and Pile\SpinScreen.cs 25 Active

After installing 3.7.0.1041
any ideas?

It’s possible this function is directX/OpenGL specific.

Either way it’s super bad in terms of performance to read from the backbuffer like that. The others already mentioned drawing to a render target first would be a good idea (a relatively simple code that used that you can find here https://github.com/Kosmonaut3d/ColorGradingFilter-Sample/blob/master/ColorGrading%20Sample/ColorGradingSample.cs, maybe check out the solution). Reading data from these textures is 100% possible, but a bit slow, too.

It all depends on what you really want to do with the backbuffer data.

figured out the error i was being a dumbass.
The method being used will be a one off capture, then transferred to an RT, nothing else in the game will be running, basically game-over, i’m using rendertargets elsewhere tied into viewports for mobile compatability, seems a shame to re-write a ton of code just for a game over screen effect (capture, copy to RT, spin and scale RT, display RT, game-over)
next time, yes, RT from the start to avoid all this
Thanks

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Yeah, that function is I think mostly useful for cases like this where you want to make a screenshot of the game. It’s definitely not something you want to run every frame.

It’s thanks to this thread I was able to do a glass transparency effect in MG using the GraphicsDevice.GetBackBufferData() method to capture an area of the screen to apply the blur effect to. Can confirm it’s running at 60 FPS for me doing it every frame, you just need to avoid reallocating the texture and pixel data array every frame and only reallocate them when their sizes need to change. There’s no need for a render target at all, just a plain old Texture2D.

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Still would be a lot better for performance to directly render your background with the blur effect though. GetBackBufferData on OpenGL might perform a lot worse on some systems depending on drivers.

Noted - I’ll keep that in mind for my engine. I’m thinking of getting the engine to render everything in an RT just so I can do post-processing on the game if I choose, so maybe I’ll have to adjust the APIs so I can get that internal RT as a texture.

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Yeah, render to RT for post is always a good idea