Please HELP-Reduce render time with compositing tags...

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  04 April 2012
Question Please HELP-Reduce render time with compositing tags...

I have prepared a little animation for render, but it takes over an hour just for a single frame...
My scene consists of some buildings a tree and one character...The only thing that is animated is my character...so, I was thinking if i could get away with rendering only my character for all frames,the environment just once and then composite them...
I know that i can do that with compositing tags, but i'm having problems how to set them correctly...I don't know how to get, in addition to the animated character, his shadows and reflections on the buildings for all frames..?
Any help will be much appreciated..Thanks in advance
 
  04 April 2012
Why not bake all the lighting on all the other objects? I have done this on several projects and reduced the rendering time of complex scenes from several minutes to several seconds without a problem. This also alows you to still have your character cast shadows and reflections!
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  04 April 2012
Josh Johnson has a video tut on compositing shadows onto a background plate. I think that should work for you if you render out your background as a still.

http://vimeo.com/30716126

Also, if your character is obscured by any foreground objects during its animation, you will need to add a compositing tag (Matte Object) to those objects. That way the alpha of your character will render out correctly. Either that or assign an Compositing Tag>Object ID to create a separate alpha for those objects and fix all the object overlaps ini compositing.
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  04 April 2012
If your scene is simple, as you seem to imply, you must have overkill render settings or a pretty slow computer. 1 hour per frame is a lot for 3 objects, unless they are crazy detailled with lots of complex shaders or very high resolution.

Are you using GI ? Physical Render ? Indirect Illumination ? Many bounces ? Blurryreflections ? Aera shadows ? Ambiant occlusion ? High Antialiasing ?

About your render, I would advise to download the free and very helpful Render Elements plugin. It helps a lot rendering render passes by hiding/unhiding layers, objects, etc... and activating/disactivating all sorts of tags and render settings without the risk of forgiving half of it in the way. Look at the video on their website to understand how it works.

As far as your scene goes, it's complicated to say which would be the best way for you to render your scene without seeing the shot. Some things can be tricked, some not depending on camera movement, occlusion of foreground/background, materials (reflection/refractions...).

It could be a combination of multipass renders, compositing tags, baking, projection mapping...
 
  04 April 2012
Originally Posted by EricM: If your scene is simple, as you seem to imply, you must have overkill render settings or a pretty slow computer. 1 hour per frame is a lot for 3 objects, unless they are crazy detailled with lots of complex shaders or very high resolution.

Are you using GI ? Physical Render ? Indirect Illumination ? Many bounces ? Blurryreflections ? Aera shadows ? Ambiant occlusion ? High Antialiasing ?


my guess would be ALL of the above - it seems to be a curse now that every new(er) user turns on every checkbox and feature with no regard or understanding of what they do or how they affect the scene or render time - the "more must be better" school of thought.

in reality i see more users do nothing but fight with GI settings on the render farm - with a very high percentage of them literally running back to back renders, over and over and endless tests to try to get rid of flicker and then in the last minute clutch for time they often just dump the GI and fake it to get decent render times and flicker free results... (which i often suggest at the very beginning of the GI re-render patterns)

it's both frustrating and kinda humorous as the situation repeats over and over... i'd like it if maxon either looked seriously at their GI defaults or settings or somehow could help educate or inform about the issues with their tools... i sure miss paper manuals as it seems nobody really reads the online manuals so a lot of the real "info" on tools and their settings is just purely missed or passed over.

it's a shame really as the "feature race" had not really done much to help new users understand just what all these new features are for or how to effectively use them.

dann
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  04 April 2012
Thank you all for your replies !

@cglittenberg
When you say bake the illumination on the other objects ,do you mean bake the objects with illumination activated? I tried that but it seems that it doesn't take into account GI...or maybe I didn't got it right...

@mustardseed
That was the approach I thought it would fit best from the beggining...Unfortunatelly this shadow catcher technique, doesn't support Physical renderer which i use in this project...
Also I was wondering with this approach how can you catch the reflections of ,let's say the character on the facades?

@EricM
Well, the "unless..." you mentioned applies for my scene...it is simple to conceive,but has some architectural details, and the building in focus is actually a store ,with some detailed objects (products) behind its glass facade...So I should had said it is a somewhat heavy scene Also I want it on 1280x720 HD res
I'm using Physical (no DOF or MB) with Indirect (1 bounce) and AO...but I'm aware of how their settings affect rendering time vs quality, and how to set them fairly wisely...It was a conscious decision..Same goes for the materials which are not that heavy (no blurry reflections,displacment...)
As for the plugin you posted, thanks a lot ! It looks really usefull !

@dann_stubbs
Guessing ,most of the times, leads to frustration...
I'm learning new stuff everyday (and I hope it stays that way) ,but I consider myself definitely not a new(er) user...although I feel your thoughts about new users or new features...
 
  04 April 2012
Transparency with Render Tags

When I first read this thread I thought it was about finding a way to make frames using Render Tags to control transparency render faster. We have a job in which all the files render at a decent speed considering poly counts and the use of a few advanced render features such as AO and Vector Motion Blur. We're not using GI or anything else render intensive.

However, we ran into a huge render hog in a scene in which we're very close to a complicated model which is textured with reflective anistropic shaders and we're fading sections of it gradually using Display Tags. Render times when thru the roof. Over 36 hours per frame at one point!

And since we're rendering on Render King we probably look like newbies to Dann. Obviously we're reworking those frames to render differently, but they still couldn't be considered speedy.

Word of warning, Evaluate Transparency in AO is a TIME KILLER! And highly reflective aninistropic metal that's slowly fading is another no, no.

Terry
 
  04 April 2012
Baking takes Gi into account with "Surface color"

You could also simply use camera projection : do a coverage render and reproject onto simple geometry from the same cam, then add a compositing tag with "compisiting background" to catch the shadows.
 
  04 April 2012
Originally Posted by YiannZ: I have prepared a little animation for render, but it takes over an hour just for a single frame...
My scene consists of some buildings a tree and one character...The only thing that is animated is my character...so, I was thinking if i could get away with rendering only my character for all frames,the environment just once and then composite them...
I know that i can do that with compositing tags, but i'm having problems how to set them correctly...I don't know how to get, in addition to the animated character, his shadows and reflections on the buildings for all frames..?
Any help will be much appreciated..Thanks in advance



i think you mentioned it does have GI and a lot of glass (in the buildings?) you did not really describe the scene in that much detail originally - but if this is so

then add a compositing tag to all the glass surfaces and uncheck the seen by GI - as transparent surfaces like glass will add nothing to the GI solution but their computation will add a ton of time to the render.

maybe that small tip alone will help speed it up? (although i have not done this with the new physical renderer - so can't 100% say it still works?) should be easy enough to try a single frame and see if the speed improves...

dann
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Dann Stubbs - dann@darkskydigital.com
http://www.RenderKing.com Value Priced C4D, VRAY, Cycles4D Render Farm
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  04 April 2012
if your scene has glass then go into "Render Setting/Options" and lower the "Ray Depth" and lowering the "Shadow depth" might help also
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  04 April 2012
Render Finished

Thank you All for your help !

I finally managed to reduce considerably the render time with a combination of some of the tips you gave me...
For most frames the most appropriate tip was by EricM, with the camera projection...I punch myself in the face for I hadn't thought about that tip...It was really obvious and simple!
So Thaks EricM and cheers !Also you were right about GI calculation during baking...I don't know what I did wrong the first time...

@dann_stubbs
It seems like with the physical renderer, it doesn't make any difference if "seen by GI" is disabled for transparent surfaces...Thanks though, as I didn't know that for Advance Renderer...
Also another tip for transparent surfaces, was to disable "seen by AO" in the composite tag...It reduced some time...
 
  04 April 2012
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