Missing documentation page

Started by DutchDimension, February 26, 2020, 01:56:28 am

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DutchDimension

What happened to the Compositing Terragen Render Elements page. I could swear there used to be content there, but now it's another empty page.

link

DutchDimension

I'd love to better understand the reasoning behind TG's RGB nature of cloudAlphas as opposed to simply single channel alphas.

KyL

This is weird, I don't know where this page went either  ???

But here you will find some useful information to answer your question!

ackdoh

Quote from: KyL on February 26, 2020, 09:42:56 amThis is weird, I don't know where this page went either  ???

But here you will find some useful information to answer your question!

That is a great thread to explain RGB alphas. But still to someone new in Terragen, it can be highly confusing especially when the documentation is gone. Anyway to update the compositing wiki with examples of how to composite elements back correctly and have that explanation from the thread added as well @Matt ?
Senior Cinematic Artist
DMP/Lighting/Compositing
http://davidluong.net

DutchDimension

Thanks KyL. I figured it had something to do with refraction/scattering, but didn't have time to figure out how to make it work, so I just ShuffleCopy-ed the Red channel into the Alpha. It'll do for now.

I thought a renewed effort was undertaken a while back to improve the documentation? Didn't they hire someone do help out? I've seen a few new additions since then, including from Matt himself, which is always a good thing. But man... it still moves at a glacial pace.  :-\

Kevin Kipper

The simplest example of combining render elements to match the Terragen beauty pass, which is sufficient for many projects, is this: tgRgb = tgSurfRgb + tgAtmoRgb + tgCloudRgb

See attached: CmpRndElm_01_tgSurf.jpg

Note that each of these render elements are blended or merged together in an "additive" way, and that the end result matches the Terragen beauty pass.  Sometimes you'll want to adjust or fine-tune your image, so each of the three "Rgb" render elements above can be recreated by combining other render elements.  The newly combined elements then replace the "Rgb" render element in the comp.

There are two methods for recreating the "tgSurfRgb'' element.  The first gives you control over direct and indirect lighting.  The second gives you control over the diffuse and specular as well.  
For control over direct and indirect lighting on a surface use: tgSurfRgb = tgSurfDirect + tgSurfIndirect.  
For control over the diffuse and specular lighting on a surface choose this:  tgSurfRgb = tgSurfDirectDiff + tgSurfDirectSpec + tgSurfIndirectDiff + tgSurfIndirectSpec
Using either of these methods results in matching the Terragen beauty pass, and adds the ability to "dial in" the amount of surface lighting you want.  

Likewise the atmosphere "tgAtmoRgb" render element can also be recreated by combining the tgAtmoDirect and tgAtmoIndirect render elements, which will give you control over the atmosphere's direct and indirect lighting:  tgAtmoRgb = tgAtmoDirect + tgAtmoIndirect

And finally, the clouds "tgCloudRgb" render element can be recreated in a similar fashion, by combining the "tgCloudDirect" and "tgCloudIndirect" render elements:  tgCloudRgb = tgCloudDirect + tgCloudIndirect

See CmpRndElm_06_ReplaceAll.jpg

We're working on a Wiki document for all this and we'll cover the tgAlpha render elements in that.

DutchDimension

Hi Kevin,

thank you for taking the time replying. I think the concept of recreating the RGB passes is pretty well understood as the math is straightforward. Just add everything up.
Where things get a bit muddier is when you need to combine multiple render layers. Punching hold-outs for clouds into the atmosphere of other layers using the tgAlpha.

What I'd like to see from PlanetSide going forward (and what I and many others have been asking for years and years... and we're still not getting) is in-depth documentation of any and all new features made available at the same time as said features are released with new builds. Not 2-3+ years down the line with partial explanations scattered across the PlanetSide forum.

Most environment artists working on commercial projects do not have time to try and figure out every undocumented feature through exhaustive experimentation. We have 2-3 days to put a shot together from scratch and maybe a few more days to render/comp it before we have to move on. Which means that undocumented features will get ignored unless their applicability is obvious and straightforward. Which, lets be honest, in Terragen, is rarely a given.

To give you a simple example, there is still no explanation at all for the tgCloudPos element. None! Despite the feature being inside TG for... 7 years! Now I know what I want to use it for (comping and relighting) But using it straight out of the box with Nuke's PositionToPoints node does not work correctly. (Points are not in the same coordinate space as the imported camera with which the shot was rendered in TG). So how is the data encoded? No information. I have very little time to troubleshoot it. If I can't figure it out in time, I'll have to drop it and move on.

So to be perfectly honest, the "we are working on it" comment has lost most of its merit here because we've heard that for years with very little to show for it.

Many thanks.

Matt

Quote from: DutchDimension on March 02, 2020, 11:09:58 pmTo give you a simple example, there is still no explanation at all for the tgCloudPos element. None! Despite the feature being inside TG for... 7 years! Now I know what I want to use it for (comping and relighting) But using it straight out of the box with Nuke's PositionToPoints node does not work correctly. (Points are not in the same coordinate space as the imported camera with which the shot was rendered in TG). So how is the data encoded? No information. I have very little time to troubleshoot it. If I can't figure it out in time, I'll have to drop it and move on.

I hear you. But in case you need it next time, tgCloudPos is encoded in world space, which I think is what you expected. But it's in TG's coordinate system so you need to flip the Z for Nuke (multiply Z/blue by -1).

It's tricky to get good results from PositionToPoints with tgCloudPos because each pixel is a weighted average of all the points visible in that pixel. Overlapping clouds will break the effect. It might work if the clouds are dense enough and you get a clean view without any interference from other clouds.

QuoteSo to be perfectly honest, the "we are working on it" comment has lost most of its merit here because we've heard that for years with very little to show for it.

Acknowledged.
Just because milk is white doesn't mean that clouds are made of milk.