Explanation on noise in height texture when color values are the same?

JohannTheCreator

Hey guys. I was wondering if someone could explain why this noise is showing up on this alpha texture pictured. I've went into photoshop and sampled all over the place and the most it ever changes is like, 1/255th once in a while. For example, one spot is 167, then once in a while I get a 166. So pretty much the same color, and even if those changes are affecting it, I don't think it would be as much as to produce that much noise. So wondering if anyone could explain this. I've thought maybe it had something to do with bit depth? The alpha is 8 bit, but I would think if those areas are virtually all the same values, it shouldn't cause that much noise.  And I've also tried the alpha in multiple programs (Substance designer, painter, and blender) to make sure it wasn't something with the application causing it. 

Appreciate any input, guys. Have a good one.

Michael Knubben

Just to make this easier for people to find and answer: what you're talking about is a height (displacement) texture, not an alpha (which would most commonly be used to mask transparency). I can change the thread title if you like.
As for the noise, have you tried exporting it at a higher bitdepth?
Also, a slight blur could probably help a lot, and it will make your bevels less sharp, which will likely look better.

JohannTheCreator

Michael Knubben said:

Just to make this easier for people to find and answer: what you're talking about is a height (displacement) texture, not an alpha (which would most commonly be used to mask transparency). I can change the thread title if you like.
As for the noise, have you tried exporting it at a higher bitdepth?
Also, a slight blur could probably help a lot, and it will make your bevels less sharp, which will likely look better.

Hey Michael, sorry for the confusion. I guess a better way of saying it would be an alpha stamp or alpha brush? But yeah, I'm using it as a displacement map. And as for exporting it at a higher bit depth, this is just a texture I got online. I don't have the original sculpt / source. But I still don't understand if those grey areas are virtually all the same value, why it produces that much noise. And yeah, blurring would help, but I guess I'm just trying to understand why it's doing this on a technical level rather than using the texture in practice right now. 

This is where I got the texture from in case anyone wants to play with it on their own:
http://www.badking.com.au/site/shop/featured-products/techalpha-setby-quadspinner/

Thanks for the suggestions.

radiancef0rge

Looks like maybe compression artifacts to me, what format is the texture in? Maybe try plugging it into a grayscale gradient map to see if you can reduce the noise. 

JohannTheCreator

radiancef0rge said:

Looks like maybe compression artifacts to me, what format is the texture in? Maybe try plugging it into a grayscale gradient map to see if you can reduce the noise. 

Ah, that could be something. It came as a psd and I've tried using the psd and an exported png and it's the same result. From the website it looks like these were done in zbrush. I'm not that familiar with how zbrush works getting sculpts turned into these alpha stamps / maps. Is it possible somewhere in the process some bad compression stuff happened with that?

radiancef0rge

yeah, its possible. another thing you could try is using the quantize node and setting the number of grayscale values you would like. the map looks simple enough that this might work for you

JohannTheCreator

radiancef0rge said:

yeah, its possible. another thing you could try is using the quantize node and setting the number of grayscale values you would like. the map looks simple enough that this might work for you

Ok. Appreciate the help. I'll keep that in mind, but like I said replying to someone else, I was just curious why this was happening more than wanting to use this in practice right now. Thanks for the tip, regardless. 

JohannTheCreator

Michael Knubben said:

Just to make this easier for people to find and answer: what you're talking about is a height (displacement) texture, not an alpha (which would most commonly be used to mask transparency). I can change the thread title if you like.
As for the noise, have you tried exporting it at a higher bitdepth?
Also, a slight blur could probably help a lot, and it will make your bevels less sharp, which will likely look better.

And I just realized I completely skipped over your offer to change the thread for me. Sorry. But yeah, if you think that would get more eyes on it, I would appreciate it. 

Michael Knubben

I added a question mark as well, in case people that actually know about this will skip it thinking it's an explanation.

JohannTheCreator

Michael Knubben said:

I added a question mark as well, in case people that actually know about this will skip it thinking it's an explanation.

Appreciate it. 

Quack!

In substance Designer, can you force the bitmap mode to be 16bit instead of the 8bit it defaulted to?

JohannTheCreator

Quack! said:

In substance Designer, can you force the bitmap mode to be 16bit instead of the 8bit it defaulted to?

Tried that. Also tried switching to 16 bit in photoshop before exporting. Same result.

Quack!

With all of those set then, it must be inside of the source heightmap. A rebake of that map with better filtering / higher bit depth may be needed.  If you don't have access to the OG files, then remaking that heightmap with better values should only take a couple hours.

JohannTheCreator

Quack! said:

With all of those set then, it must be inside of the source heightmap. A rebake of that map with better filtering / higher bit depth may be needed.  If you don't have access to the OG files, then remaking that heightmap with better values should only take a couple hours.

Yeah, that seems to be the consensus so far. Appreciate the help. 

Noren

JohannTheCreator said:

 I've went into photoshop and sampled all over the place and the most it ever changes is like, 1/255th once in a while. For example, one spot is 167, then once in a while I get a 166. So pretty much the same color, and even if those changes are affecting it, I don't think it would be as much as to produce that much noise.

"Pretty much the same color" is not the same color. 166 height layers aren't that many (so for your object it's a 1/166th deviation in visible height) and I wouldn't be surprised to see some noise, especially when it comes to specular/reflections, which amplify any change in surface normals.
You could try to fill parts of the top with a solid color to exclude that possibility, though.
(Basically what radiancef0rge suggested, but used for analysis.)