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#ActualTelanor

Posted 28 August 2012 - 01:32 AM

Sure that's the point. I do luminance downsampling but the initial sampling is made on the whole HDR image and not on the DownscaleRenderTarget. The downside is that it has a slight impact on the performance.


Ok so instead of starting at the 1/16th size image, you started from the fullsize image, calculated the initial luminance using the function you provided, and then downscale it to a 1x1 to get the average? Correct me if I'm wrong but the code you provided seems to sample the same pixel 9 times. Is that intentional...?

The result rendertarget in the function is 1/16 size of your source image and the PostProcess() is called 4 times. The first 3 time you call it on a temporary rendertarget which is 1/2 of the last ones size. So you have 1/1 -> 1/2 after the first pass and then 1/2 -> 1/4 -> 1/8 and then it is rendered to the result rendertarget and you get your 1/16 sized texture.


I had figured that was the intention but it's not actually using the size of the previous RT, but continually using the size of the source RT. I checked with the debugger, source.width / 2 is the same number for all 3 RTs. I'm guessing thats a bug in the sample then.

#2Telanor

Posted 28 August 2012 - 01:31 AM

Sure that's the point. I do luminance downsampling but the initial sampling is made on the whole HDR image and not on the DownscaleRenderTarget. The downside is that it has a slight impact on the performance.


Ok so instead of starting at the 1/16th size image, you started from the fullsize image, calculated the initial luminance using the function you provided, and then downscale it to a 1x1 to get the average? Correct me if I'm wrong but the code you provided seems to sample the same pixel 9 times. Is that intentional...?

<br />The result rendertarget in the function is 1/16 size of your source image and the PostProcess() is called 4 times. The first 3 time you call it on a temporary rendertarget which is 1/2 of the last ones size. So you have 1/1 -> 1/2 after the first pass and then 1/2 -> 1/4 -> 1/8 and then it is rendered to the result rendertarget and you get your 1/16 sized texture. <br />


I had figured that was the intention but it's not actually using the size of the previous RT, but continually using the size of the source RT. I checked with the debugger, source.width / 2 is the same number for all 3 RTs. I'm guessing thats a bug in the sample then.

#1Telanor

Posted 28 August 2012 - 01:31 AM

Sure that's the point. I do luminance downsampling but the initial sampling is made on the whole HDR image and not on the DownscaleRenderTarget. The downside is that it has a slight impact on the performance.


Ok so instead of starting at the 1/16th size image, you started from the fullsize image, calculated the initial luminance using the function you provided, and then downscaled? Correct me if I'm wrong but the code you provided seems to sample the same pixel 9 times. Is that intentional...?

<br />The result rendertarget in the function is 1/16 size of your source image and the PostProcess() is called 4 times. The first 3 time you call it on a temporary rendertarget which is 1/2 of the last ones size. So you have 1/1 -> 1/2 after the first pass and then 1/2 -> 1/4 -> 1/8 and then it is rendered to the result rendertarget and you get your 1/16 sized texture. <br />


I had figured that was the intention but it's not actually using the size of the previous RT, but continually using the size of the source RT. I checked with the debugger, source.width / 2 is the same number for all 3 RTs. I'm guessing thats a bug in the sample then.

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