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Author Topic: PBR textures  (Read 15412 times)

igor73

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PBR textures
« on: May 05, 2015, 01:28:30 PM »
Planning to make some of my own tiled PBR textures based on scan data.  Will start out with some wood materials. 

Does anyone have a good method for generating accurate specular and gloss / roughness maps?  Normal maps  i plan on using Xnormal or Zbrush  as i have done on scanned objects.  Will use the texture/materials for UE4 and Octane render. 

Need to get rid of or reduce AO from the diffuse and i will try using HDRi tone mapped images for this purpose.   I also have large soft boxed strobes available for even lighting.  Any advice on this?


igor73

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Re: PBR textures
« Reply #1 on: May 05, 2015, 01:48:34 PM »
Searching  a bit and found a method using polarizing filters to separate diffuse.  Not sure how this will work in a single camera photo scanning scenario though? 

http://filmicgames.com/archives/233

bigben

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Re: PBR textures
« Reply #2 on: May 05, 2015, 05:24:26 PM »
You might find this interesting;
https://www.youtube.com/watch?v=clakekAHQx0

igor73

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Re: PBR textures
« Reply #3 on: May 05, 2015, 06:33:25 PM »
Seen the video and its a very interesting overview.   They do not give much in depth info on how they cancell out AO and create accurate specular maps though.  Anyone have ideas? 

bmc130

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Re: PBR textures
« Reply #4 on: May 05, 2015, 11:08:01 PM »
I use lightbrush to cancel out shadows/highlights in textures. Works pretty good.

Allegorithimic have AO/shadow exclusions in their bitmaptomaterial 3 software. Don't know how good it does it though.

When it comes to the specular parts/generation I would love to know a good way of generation those aswell :)

igor73

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Re: PBR textures
« Reply #5 on: May 06, 2015, 01:52:50 AM »
Thanks for the tip on lightbrush, looks very interesting.  Do you feel this allows you to lift a lot more shadows than camera RAW on good DSLR images?  I guess so or you would not use it.   

http://www.fxguide.com/featured/tandent-lightbrush-engineering-an-image/

driftertravel

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Re: PBR textures
« Reply #6 on: May 06, 2015, 05:46:28 AM »
Lightbrush works much better than camera raw when you learn how to use it. The downside is that it works much better on raw images, so to get the most out of it you have to batch each of the photos that you use in photoscan before you project the texture, which takes almost as long as processing with photoscan. You can use it on the tiff texture that photoscan produces, provided it's 16bit, but it doesn't work quite as well. That, and it's expensive ($800, down from $2500) and mac only.

edit: oh, and it doesn't work well on HDR images at all. You would need to run it on each of the images before combining and hdr tonemapping them.
« Last Edit: May 06, 2015, 05:48:48 AM by driftertravel »

bmc130

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Re: PBR textures
« Reply #7 on: May 06, 2015, 09:31:56 AM »
thats correct driftertravel! From an email I got from tandent on the licensing matter they told me this:

Lightbrush 1.1 Sandbox (Mac)                                                         $99.00
Image size limited to 1000 px
 
Lightbrush 1.1 Regular (Mac)                                                          $395.00
No image size limits.
 
Lightbrush 1.1 Professional (Mac)                                                  $895.00
Batch processing and no image size limits.

I use lightbrush on pretty much everything, I agree sure you would get a better result working on raw,I use it on the 16bit tif that agisoft generates, doing it on the photos is too time consuming. To me it's a time saver when doing textures for games, sure if you have clamped areas in shadows/highlights it wont save you.
I often use it when making tilable textures as well, when you sometimes get this soft variations in lighting (upper corner have tiny light variation/blend compared to the bottom left) which makes you texture tile. Instead of trying masking and level this out in photoshop, lightbrush can help me with it.

And when you process an image you get the extracted light/shadow information in a separate image, multiplying that on top of you diffuse in photoshop you get the same result as the original texture, but now you can blend shadows back with opacity or paint back information with masking if you want too.

Yes it's not perfect but, if needed, together with regular photoshop works shadows/highlights etc I usually get what I need.

The annoying part is Tandent decided for some reason to make it mac only, they had PC when I bought it.

Wishgranter

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Re: PBR textures
« Reply #8 on: May 06, 2015, 11:33:10 AM »
BMC thanx for the info, as i have tested it on my dual xeon approx a year back get very very slow processing, say 5-7+ min on 18Mpix RAW image, whats your times on MAC ?
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bmc130

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Re: PBR textures
« Reply #9 on: May 06, 2015, 11:42:25 AM »
Wishgranter, I have an older license for PC so I dont run it on mac. And I rarely (never) use it on any raw photos. I use it only on the generated texture from agisoft. But yes the times you say is about right. An 8K texture takes about 10min that to process. An 4K texture is a couple of minutes.

Marcel

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Re: PBR textures
« Reply #10 on: May 06, 2015, 01:56:01 PM »
Seen the video and its a very interesting overview.   They do not give much in depth info on how they cancell out AO and create accurate specular maps though.  Anyone have ideas?

Epic's specular maps must be generated based on diffuse / depth data, there is no way to extract specular data without using very controlled lighting conditions (ie. a light dome, totally different technique).

I think they cancel out AO/environment light by simply baking the lighting info from the lightprobe  (you can convert a mirror ball image to a spherical HDR map) to a white mesh.  If you substract this lighting info from the texture map generated by Photoscan, you should have a texture with a neutral lighting.

driftertravel

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Re: PBR textures
« Reply #11 on: May 06, 2015, 08:54:57 PM »
Epic's specular maps must be generated based on diffuse / depth data, there is no way to extract specular data without using very controlled lighting conditions (ie. a light dome, totally different technique).

According to Epic, they make specular maps with a cavity bake. Has worked pretty well for me in the past:

https://docs.unrealengine.com/latest/INT/Engine/Rendering/Materials/PhysicallyBased/index.html

"Commonly, if we modify Specular, we do so to add micro occlusion or small scale shadowing, say from cracks represented in the normal map. These are sometimes referred to as cavities. Small scale geometry, especially details only present in the high poly and baked into the normal map, will not be picked up by the renderer's real-time shadows. To capture this shadowing, we generate a cavity map, which is typically an AO map with very short trace distance. This is multiplied by the final BaseColor before output and multiplied with 0.5 (Specular default) as the Specular output. To be clear this is BaseColor = Cavity*OldBaseColor, Specular = Cavity*0.5."

Basically I multiply a cavity bake over the base specular for the material in question, then screen an edge highlight map over that. Since specular doesn't do a helluva lot in UE4's renderer it works just fine.

mrrafs

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Re: PBR textures
« Reply #12 on: September 15, 2015, 01:09:25 PM »

there is no way to extract specular data without using very controlled lighting conditions (ie. a light dome, totally different technique).
[/quote]

have about this method? www.lebedev.as/pdf/papers/LebedevGraphicon2008.pdf

as long as you have hdr images and an image with light direction (i.e. chrome sphere or 360 pano with camera position), this method provides spec?

sc

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Re: PBR textures
« Reply #13 on: September 15, 2015, 02:50:32 PM »
Don't confuse specular with smoothnes/roughness maps when talking about PBR. In that showcase from Epic, they use their red channel from their basecolor as a base for their roughness map, which is not the way to do it at all. Processing your RAW files is essential, where you remove shadows and highlights, chromatic abberation and vignetting etc.