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user88

Member Since 17 May 2009
Offline Last Active Jul 16 2014 02:56 AM

Posts I've Made

In Topic: [DX11] Why we need sRGB back buffer

16 June 2014 - 09:47 AM

Okay, with implementation of Gamma Correction as well as backbuffer sRGB format all is clear for me now.

 

Great post, Chris:

 

http://www.gamedev.net/topic/652795-clarifications-gamma-correction-srgb/#entry5127278

 

Hodgman, your post also was very helpful, thanks. One point is not clear for me. It is about "mathematically linear" and "perceptually linear" things:

The reason you think the first image is 'correct' is because "mathematically linear" is not the same as "perceptually linear". In order to perform correct lighting and shading calculations, or to be able to reproduce the same photograph that we captured earlier, we need all the data to be mathematically linear.

 

  - Why the linear gradient that i can see on screen looks like non-linear with gamma correction (second case in my first post)? I compared it visually with linear gradient that i have made in PhotoShop. Same width in pixels. On screen looks different. Is there some PhotoShop trick?


In Topic: [DX11] Why we need sRGB back buffer

16 June 2014 - 01:49 AM

 


I thought that sRGB backbuffer is like JPEG in sRGB color space, meaning that all values in sRGB buffer are already Gamma Corrected (pow(value, 2.2)). If so, then final color values should outputted with pow(value, 2.2) correction. But no, it seems the sRGB backbuffer is the opposite of what I thought.
No, the display/monitor itself does the pow(value,2.2) itself, in the display hardware.

If you do the pow(value,2.2) yourself, then you end with seeing pow(pow(value,2.2),2.2) after the display emits the picture biggrin.png

 

I mean 1/2.2 not 2.2. Already corrected my previous post. Sorry for that..


In Topic: [DX11] Why we need sRGB back buffer

16 June 2014 - 01:33 AM

Have you read the article "The Importance of Being Linear"?  It does a pretty good job of explaining why you need gamma correction, including the situations when you should use it and when you shouldn't.  I applaud the OP's willingness to experiment, but in this case it seems like you don't get the high level concept just yet - so please try to read through that article and come to a mathematic reasoning for doing this and then the correct operation will be quite clear.

 

Hi Jason,

 

I have read this article (anyway thank you for a link) and understand the mathematic reasoning of Gamma Correction process. All is clear for me with sRGB images sampling and correction for further linear calculations. All intermediate calculations should be outputted to buffers with any correction. That is also clear for me.

 

The misunderstanding actually is with sRGB backbuffer. I thought that sRGB backbuffer is like JPEG in sRGB color space, meaning that all values in sRGB backbuffer are already Gamma Corrected (pow(value, 1/2.2)). If so, then final color values should outputted with pow(value, 1/2.2) correction. But no, it seems the sRGB backbuffer is the opposite of what I thought. Furthermore, final color value should be outputted with pow(value, 1/2.2) correction for non-sRGB backbuffers, right?


In Topic: [DX11] Why we need sRGB back buffer

13 June 2014 - 06:00 AM

Hello Ashaman73, as I understood you are talking about sRGB color space and HDR, but my question is about advantage sRGB backbuffer + pow(u, 2.2) over non-sRGB format  + direct output.

 

What I can guess from comparison image (last one in my first post) the advantage is in precision of Gamma curve applied to final image. With sRGB backbuffer + pow(u, 2.2) it is more precise. Right? Are there any other advantages?


In Topic: 'usp10.h' no such file or directory

24 February 2014 - 02:30 AM

After short googling I have found discussion about the same problem: http://social.msdn.microsoft.com/Forums/en-US/51823ee4-018c-44d9-a5ef-7c99e64979e5/vc-2005-express-want-to-build-dxsdk-sample-usp10h-missing?forum=gametechnologiesgeneral

 

I hope that will help you.


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