Preventing hangup on long renders?
arcady
Posts: 340
Its happened to me twice now where I have left a 2-3 hour render running over night - come back in the morning and there are a few blocks somewhere in the middle of the render that are still the little colored boxes, and the render won't save as it still claims to be in progress...
I then let it sit for another hour and it never moves an inch. I check and my drives are all on, everything is on, and the app is still responsive.
But when I hit abort, it locks up, so I can never save even the 99% done image (was planning to comp it all together in photoshop by saving a series of them).
How can I prevent this?
Is there a pause or resume render button anywhere?
Any tips on what might be causing it?
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Comments
There is a way to pause the render but only if you're doing it as a batch render.
I'm sorry, I do see people from time to time who run into this problem, but it's one of those things that's never happened to me, so I don't have much good advice to give. Hopefully some others will chime in.
This happens to me too. I discovered, in my case at least, that it was related to the textures on one of my figures. The texture was layered, and each layer had its own instance of subsurface scattering. If I had more than one instance of SSS turned on at a time then this would inevitably occur. Some angles were worse than others but I could never get a render to complete when all the sss was turned on more than one layer. Near as i could figure is that scattering on multiple layers was causing a break in the calculation. Not sure if this helps in any way, but you are definitely not alone.
Use a vertex plane in front of your camera to mask the serene into smaller. Lots.
Turn off shadows for the plane, give it no colour etc, remove the ploys where you want to render
Serene is scene .do t you hate autofill
I don't know what causes it. I do the following and that has cut out most of my crashes.
1. Turn invisible (or delete) any item that is not in the scene.
2. Turn invisible any body part hidden by clothing.
3. Empty out the TMP folder
4. Shrink the size of the Render blocks to 99
5. BATCH Render your scene (this frees up memory so your computer doesn't work so hard).
Try these things to see if that helps.
It can also occur where we might have stacks of shaders in a particular part of the scene that can cause the cores hang there for long periods. I've seen this where I have a lot of trans-mapped hair over eyes with intense shaders on all of the various pieces of the eyes that require transparency, reflection, refraction, etc.,
...add to that skin with SSS and you'll see specific areas in the render that will get a few cores seemingly stuck, when actually they're just making mass amounts of calculations.
One way to try and conquer this if you have several cores rendering, without tweaking on the shaders, would be to go to the bottom of the first page in the render room, and set the "Tile Size" down to the far left of the slider. 16, I believe the value is. This will create the effect of giving each core a smaller amount of data at one time. With today's cpu speeds, it makes no sense to not do this, since each core will fly through the little 16 x 16 block and move on to its next target.
If you want to further reduce hang-ups investigate your shaders. Since alpha-mapped hair strands pretty much need their trans-maps or end up looking like a chunk of stiff ribbon, we don't really want to look there first. So lets figure out how much effect we need on glistening realism on the eyes. If the shot needs speed rendering, and doesn't really need specific reflections, we can mimic reflections using highlight and shininess and eliminate reflections altogether. For starters set the highlight all the way to 100 and the shininess to something like 22, and set reflection to 'none'. If the highlighted shines are too big, increase shininess to 30 and try again. Too small now? Try 26 or 27. Too small from the start? Try 10, etc., While this won't cause a reflection, the high white highlight will cause a shine that will mimic the effect.
Lighting:
Linking lights is a term used to make a light 'only' affect certain things, ignoring everything else in the scene.
We often take our character lighting setup and make a duplicate of each main light. Let's call the original lights A and the duplicated ones B for example sake.
Make all A lights affect the whole character, including all props and clothing, except the hair.
Make all B lights only affect the hair.
(A lights are linked to V4, all of her clothes, the sword on her side and the gun in her hand, while all B lights are linked to only the hair)
You should immediately see the problem this can cause. No shadows from the character onto the surrounding environment. The reason for doing this is that, if we let the A lights cast shadows onto "Everything except the Hair", we'll see the shadows from the character, but not from the hair!
So these special "Character Lights" need to remain less intense than lights that are meant to fully illuminate the character.
Now we make the main environmental lights affect everything in the scene, including the character. Any lights that would not catch the character in an interesting way should be linked to the environment, or to exclude the character. Basically you need to have shadows cast from the character from at least one light in the scene.
Am I carrying on too much? If so, I apologize. Just thinking out loud.
Basically what we're trying to do hear is to use special lights only for the trans-mapped hair that either does not use soft shadows, or that do not use shadows at all. This will almost completely eliminate the hangups caused by shadows being calculated through those trans-mapped polygons. So it can be very helpful if you do not require soft shadows on the light that does need to affect the character as well as the environment for the main character-to-ground shadows that the scene really needs.
In the shaders above I haven't mentioned refraction. You can either turn off refraction (if you don't need it for this shot) in the shaders or in the render room setting at the top of the first tab.
Just some stuff to consider.
The good news is Carrara let's you do "save as" at any stage of the render as often and in different formats as you like.
So you can fix it in GIMP or Photoshop if you want it now.
The trick to make a panel that did not interact with shadows and had no color - that worked to let me render just the pieces that were missing.
I've been using render blocks at size 16 since seeing PhilW's preview videos - so it was size 16 blocks that were hanging for me.
I'll keep the other tips in mind for my next project and watch to see if they're occurring anywhere. Thanks everyone.