Digital Art Zone

 
   
1 of 3
1
Indirect Light and scene scale.
Posted: 20 October 2013 09:38 PM   [ Ignore ]
Member
Rank
Total Posts:  209
Joined  2006-01-10

A while ago, the Carrara native content was reworked to better match the scale of objects in scene magnitudes. I noticed some of the GI scenes now take much MUCH longer to render on my system. Some popular scenes like the indoor House Day(etc.) used to render faster. This scene had Sky light and Indirect Light checked. I remembered some of the scenes used to be a small scale magnitude. Sure enough, when I scaled it down, it rendered faster.

For instance. On my system, the House Day scene(default) takes approximately 2hrs:25min. If I group and scale the scene down to 1% of the overall scale, then reset the group to origin(0,0,0), it now takes 1min:49seconds. While the quality degrades slightly(which appears mostly related to Interpolation being checked), its no where near that much of a difference to waiting 2 hours(example images below). At first it appeared to be the scale differences maybe linked to photon mapping etc. However, I later find this is not the case.

Sometimes when rendering a scene, I noticed depending on how I moved the objects, the render times were very inconsistant. By accident, I found that if you move a single object out to great distances, the indirect light changes in the similar way as scaling down a scene does. So the indirect light rendered much faster with this method as well, only now the quality can be inconsistant.

Example. Load the ‘House Day’ scene from the browser. Insert a sphere anywhere in the scene. Move or translate the sphere to 100k(ft) distance or more on the Z axis. Render the scene. It renders darker, but still much faster. To further test, I experimented with other outdoor scenes. It works just as well and I get very realistic results with some fine tuning.

So, scaling an overall scene down or moving an single object to great distances affect the indirect lighting renders in a similar way. I might be missing something obvious or could this just be my setup. Anyone else experience similar results?

  The first image takes approx. 1minute 49 seconds to render using the smaller scale. The second takes approx. 2 hour 25 minutes (EDIT:using the default medium scene). Both have the same default render settings.

Image Attachments
HD1m.jpgHD2h.jpg
Profile
 
 
Posted: 21 October 2013 09:13 AM   [ Ignore ]   [ # 1 ]
Active Member
Avatar
RankRank
Total Posts:  618
Joined  2009-12-08

Hi there.

Whilst I haven’t spent much time with GI (too slow for an animator), I would like to comment on scene size and render speeds.

Scene size affects lighting. The smaller you go (I’ve gone to 1%, but often I’m in 10%), the more likely shadows might become a problem (i.e. they will not be there). Usually it’s ok.

I think there are many bugs in lighting. You can almost think of this as a “feature”. For example the Glow on a bulb just isn’t big enough to do a decent street light at night (at full size), take it down to 10% and voila! Just right.

I’ve also had problems with Distant lights at full size on very large scenes. They run out! So again, rescaling the models to 10% and now the distant light goes further.

However your discovery is excellent!

Perhaps the secret now then is to render a frame at full size with render settings set to something flimsy (like no anti-ailising, low object and shadow accuracy) to get the rough idea of what it *should* look like ( I say this with a pinch of salt as the only real guide are reference photos imho), then reduce the size to knock the frames out.

GI plays up with animation though. I think this particular scene causes problems from memory (the additional lights for the lamps etc vary in performance according to where the camera is - do a pan from left to right to see what I mean).

In summary (as I feel I’m going on a bit). I prefer to see what it should look like, then fake it all with fake indirect lighting (usually tubes, but bulbs are ok sometimes) PLUS scene size. That way you can get the lights to behave differently as explained with glow above.

 

 Signature 

More 3D info and Pics at http://www.facebook.com/scififunk

Profile
 
 
Posted: 22 October 2013 12:57 AM   [ Ignore ]   [ # 2 ]
Member
Rank
Total Posts:  209
Joined  2006-01-10

Hi Sci Fi Funk.

Indirect lighting or maybe the render engine seems to have scene scaling limits. Still experimenting to find out what the limits are. I did notice the size of glow channel shaded objects will make more or less light but had not tried it at various scene scales yet.

When scaling indirect light scenes down, it does degrade the quality in some areas, but I can usually fine tune the scene or render settings to make it look better. At these massively decreased render times its worth it.

With indirect light animations, the light ends up being calculated different for each frame(afaik). This causes flickering shadows or light in some areas. If the camera is the only thing that moves, the Irradiance Map save feature should be able to avoid it. I haven’t tested with only a Sky Light yet.

Profile
 
 
Posted: 22 October 2013 01:38 AM   [ Ignore ]   [ # 3 ]
Member
Rank
Total Posts:  209
Joined  2006-01-10

The main reason I wanted indirect lighting was for more realistic scenes. I didn’t like the way some HDRI and Sky Light look as they don’t bounce color like indirect lighting does. Having only a single core system(atm), I had to find ways to decrease render times. With the above scene scaling method, I can now test or even final render scenes without the massive render times.

Below image is Howies Snow Scene with indirect light and some atmosphere adjustments. One sun light, no sky light or background. Render time was around 1hr:23min. at (EDIT:default render settings from the scene except filter sharpness at 100% and IL at 145% intensity). Reduced the image for the forum, but should still give a good example.

Image Attachments
HSS1.jpg
Profile
 
 
Posted: 22 October 2013 02:21 AM   [ Ignore ]   [ # 4 ]
Active Member
Avatar
RankRank
Total Posts:  618
Joined  2009-12-08
tbwoq - 22 October 2013 12:57 AM

With indirect light animations, the light ends up being calculated different for each frame(afaik). This causes flickering shadows or light in some areas. If the camera is the only thing that moves, the Irradiance Map save feature should be able to avoid it. I haven’t tested with only a Sky Light yet.

I see. Thanks for your insights. I’ll have a try with this at some point in the future.

We all want more realistic renders, and your kind revelation as to the time saving by scaling with GI is a great find.

 Signature 

More 3D info and Pics at http://www.facebook.com/scififunk

Profile
 
 
Posted: 22 October 2013 03:45 AM   [ Ignore ]   [ # 5 ]
Member
Rank
Total Posts:  209
Joined  2006-01-10
Sci Fi Funk - 22 October 2013 02:21 AM
tbwoq - 22 October 2013 12:57 AM

With indirect light animations, the light ends up being calculated different for each frame(afaik). This causes flickering shadows or light in some areas. If the camera is the only thing that moves, the Irradiance Map save feature should be able to avoid it. I haven’t tested with only a Sky Light yet.

I see. Thanks for your insights. I’ll have a try with this at some point in the future.

We all want more realistic renders, and your kind revelation as to the time saving by scaling with GI is a great find.

Glad it helped, and thanks for your insights and tutorials as well. The irradiance map feature is also a huge time saver for some scene setups. I think its the same as the Global Illumination Multi-Pass element.

Profile
 
 
Posted: 22 October 2013 10:06 AM   [ Ignore ]   [ # 6 ]
Power Member
Avatar
RankRankRank
Total Posts:  1694
Joined  0
tbwoq - 20 October 2013 09:38 PM

Sometimes when rendering a scene, I noticed depending on how I moved the objects, the render times were very inconsistant. By accident, I found that if you move a single object out to great distances, the indirect light changes in the similar way as scaling down a scene does. So the indirect light rendered much faster with this method as well….

So…. Carrara is creating a scene-sized “grid” and filling it in with photon elements…. Then ignoring the areas without any geometry…. And the issue of quality is related to how many photon elements are creating the light map….

Scaling down, Carrara assumes fewer photon elements - a lower resolution “grid”.

It makes sense. And you discovered how to control it: Send a primitive off into the distance to change the size of the scene….

This is amazing information!

 Signature 

320+ TUTORIALS for Carrara at CARRARA CAFE
C3DE - CARRARA 3D EXPO MAGAZINE - the showcase for Carrara Artists

Profile
 
 
Posted: 22 October 2013 11:09 AM   [ Ignore ]   [ # 7 ]
Addict
Avatar
RankRankRankRank
Total Posts:  6155
Joined  2007-12-04
holly wetcircuit - 22 October 2013 10:06 AM
tbwoq - 20 October 2013 09:38 PM

Sometimes when rendering a scene, I noticed depending on how I moved the objects, the render times were very inconsistant. By accident, I found that if you move a single object out to great distances, the indirect light changes in the similar way as scaling down a scene does. So the indirect light rendered much faster with this method as well….

So…. Carrara is creating a scene-sized “grid” and filling it in with photon elements…. Then ignoring the areas without any geometry…. And the issue of quality is related to how many photon elements are creating the light map….

Scaling down, Carrara assumes fewer photon elements - a lower resolution “grid”.

It makes sense. And you discovered how to control it: Send a primitive off into the distance to change the size of the scene….

This is amazing information!

Agreed - and I am very excited to try this for myself.
Steve, I think that, what you’ve been noticing with Distant lights (due to their infinite nature) that some elements of your scene were blocking them at full scale, but no longer when reducing the scene size. I could be wrong. Distant lights have an infinite path, so if you block that path anywhere along the grid (not just according to the placement of the light model, itself) it will create a shadow. If that shadow is large enough, it can (very easily) block the affects of the light altogether.

Back to the original topic, I’m really glad that Holly explained it in her way - as I was thinking along those same lines, when reading the discoveries in the original post, but was fumbling over an explanation! lol
That kind of time savings might just make animation and GI/IL a more useable endeavor and, like I said, I can barely wait to try it.

Once again,
thanks tbwoq! (and Holly and Steve)

 Signature 

Dartanbeck @ Daz3d          Check out the Carrara Cafe          ►►►  Carrara Information Manual   ◄◄◄

Profile
 
 
Posted: 23 October 2013 01:18 AM   [ Ignore ]   [ # 8 ]
Active Member
Avatar
RankRank
Total Posts:  278
Joined  2007-07-13

This all seems to be known as it is mentioned in the C7 Manual on page 795.
Along with this there is a hint for saving memory.

For me the question now is:
Are these supposed to be features or just workarounds for bugs in the render engine?

Eddy

 Signature 

- Live Long and Prosper -
My DAZ Gallery: http://www.daz3d.com/gallery/users/1589

Profile
 
 
Posted: 23 October 2013 02:52 AM   [ Ignore ]   [ # 9 ]
Member
Rank
Total Posts:  209
Joined  2006-01-10

-holly wetcircuit.

No idea whats happening yet when moving the objects out miles from the origin. Content like Victoria 4.2 is especially bad. I tested 25 miles away and, wow, it does something strange to the mesh or render. There was a bug reported about this issue but I can’t check the status. Don’t know if it got fixed in 8.5. I’ll continue researching and later, start testing photon maps.

-Dartanbeck.

There might well be some kind of limits or rendering precesion issues like holly said, but I’m now finding out it might have to do with all lighting. If the users with 8.5 say that the above mentioned bug with content is still happening, then there might be something in the render engine that possibly degrades the rendering precision on purpose. Why this would be, I’m not sure. The rendering precision is mentioned when creating a new document(scene).

-EddyMI.

It could well be a bug with how the render engine processes objects and scene scale or distances. Or it could just be a limitation of rendering precision in Carrara. I’m guessing at this point, that its something different from what is mentioned in the PDF manual.

Profile
 
 
Posted: 23 October 2013 03:46 AM   [ Ignore ]   [ # 10 ]
Active Member
Avatar
RankRank
Total Posts:  548
Joined  2007-08-14
EddyMI - 23 October 2013 01:18 AM

This all seems to be known as it is mentioned in the C7 Manual on page 795.

Which manual? The one I have (revision G) talks about batch rendering on page 795.

 Signature 

These are not the tutorials you’re looking for. Move along.
My old profile

Profile
 
 
Posted: 23 October 2013 05:13 AM   [ Ignore ]   [ # 11 ]
Active Member
Avatar
RankRank
Total Posts:  278
Joined  2007-07-13

I have the same Revision.
But note, that the page number in the document differs from that one that is shown in the reader because of the intro pages at the beginning of the manual. 2 unnumbered pages and 9 content pages with roman numbering and another unnumbered page. That makes the difference of 12.

Document page 795 + 12 = Reader page 807

 Signature 

- Live Long and Prosper -
My DAZ Gallery: http://www.daz3d.com/gallery/users/1589

Profile
 
 
Posted: 23 October 2013 05:18 AM   [ Ignore ]   [ # 12 ]
Active Member
Avatar
RankRank
Total Posts:  548
Joined  2007-08-14

Ugh me so dumb. Thanks.

 Signature 

These are not the tutorials you’re looking for. Move along.
My old profile

Profile
 
 
Posted: 23 October 2013 07:31 AM   [ Ignore ]   [ # 13 ]
Power Member
Avatar
RankRankRank
Total Posts:  1694
Joined  0

I do not see this info on page 795…?

<quote>
-holly wetcircuit.

No idea whats happening yet when moving the objects out miles from the origin. Content like Victoria 4.2 is especially bad. I tested 25 miles away and, wow, it does something strange to the mesh or render. There was a bug reported about this issue but I can’t check the status. Don’t know if it got fixed in 8.5. I’ll continue researching and later, start testing photon maps.
</quote>

I am feeling especially dumb this morning… The mesh is deformed? Does anyone have a pic of this?

 Signature 

320+ TUTORIALS for Carrara at CARRARA CAFE
C3DE - CARRARA 3D EXPO MAGAZINE - the showcase for Carrara Artists

Profile
 
 
Posted: 23 October 2013 07:51 AM   [ Ignore ]   [ # 14 ]
Active Member
Avatar
RankRank
Total Posts:  278
Joined  2007-07-13

Here it looks like this…

Image Attachments
CMAN.jpg
 Signature 

- Live Long and Prosper -
My DAZ Gallery: http://www.daz3d.com/gallery/users/1589

Profile
 
 
Posted: 23 October 2013 08:03 AM   [ Ignore ]   [ # 15 ]
Power Member
Avatar
RankRankRank
Total Posts:  1694
Joined  0

Yes, that is the same page I have, but it is not any of the info listed above in tbwoq’s post.

 Signature 

320+ TUTORIALS for Carrara at CARRARA CAFE
C3DE - CARRARA 3D EXPO MAGAZINE - the showcase for Carrara Artists

Profile
 
 
   
1 of 3
1