1+ Hour Quick Render
DarkSide Projects
Posts: 25
Hi there,
Could anyone please explain as to why it could be taking so long to render when I turn on Indirect Lighting? I have sat for nearly an hour waiting in the render room and the progress bar is only at 27%. Quick render takes just as long as the machine seems to hang for 15 minute intervals on a regular basis. I have tried turning shadows, reflection etc off with no difference. Everything else is perfect but as soon as I try indirect lighting the machine comes to a halt.
My specs if that will help:
i5 3330 3.0Ghz
8Gb DDR3 Ram
GTX 650 Ti
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What application and version?
Sorry about that, completely forgot :)
Im using Carrara 8.5.0.243 (32bit)
Windows 7 Home Basic 64(bit)
Im pulling my hair out lol, as this is the only thing holding me back :)
Thank you for the help!
If you like, I can move this to the Carrara forum.
Please, if you don't mind.
Thanks alot :)
Moved to Carrara Discussion forum.
Indirect lighting happens on the render end, and if you have it turned on in the render room, your spot renders will use it too. Depending on your scene, IL is one of the things that will add the most tremendous amounts of time to your renders, and really should not be used as a quick render situation. Perhaps turn IL off, do your 'quick' renders to test what you have, and turn it back on for your final render, where you walk away from your computer for a long time. Some IL render artists wait for more than a day for their renders to complete.
That all said, there are probably ways to speed up Indirect lighting renders. And again, it has a lot to do with the settings of the IL, itself. It can tax your render time, even at it's lower default settings. But turn some of those to 'good' or better, and yeah... it'll have you wait.
Carrara also has a few ways of faking IL. First, there's the "Ambient" setting in the Scene Effects area. In the Assembly Room, select the bold "Scene" in the right panel, and the top most effect setting is 'Ambient'. It's a fake IL, or actually a setting that defies shadow darkness.
Another method would be to visualize your own IL, and create it yourself using a light, like a distant light, for example, and turn shadows off. Or if you would like some shadows from it (IL doesn't actually cast shadows) you can set the light to only affect certain parts of the scene - or it may be easier to just have it ignore objects that would otherwise block it. But to simulate IL in this manner, simply turning off shadows, setting the color, and turning the brightness down is an easy, yet effective artificial IL. Some of us even use two or more lights in this manner - for added color and effect.
Another thing that can really slow down your renders is soft shadows and blurry reflections. Shadows and reflections slow down render times anyways. But make shadows soft and/or reflections blurry, and you're asking for Carrara to do a lot of math for each pixel painted.
Keep in mind that this is difficult to just give an easy answer, as I have no clue what you're rendering - even just saying what you're rendering isn't much to go on without knowing how the lights and shaders are all set up. how much stuff is in your scene, what effects are being used, believe me when I say that 3D rendering engines can easily bring a top-spec computer to its knees with little effort, not just Carrara with IL turned on.
I hope that I gave you some help in one way or another. If not, let me know what else you'd like to know and we'll dig up some answers :)
Take care and good luck!
Thanks for this, this helps a lot :)
I spoke to a friend of mine as well, who is a professional graphic designer, and he pretty much said exactly what you have here. Indirect lighting will take ages to render and should be left for final renders and if it is quite a large scene, be prepared to wait a long time :)
At least no i know where i was going wrong! Thanks :)
One thing you can do is to set up your scene the way you want with the lighting you want. When you are ready to render your scene with the full GI (Indirect Lighting) render a low res version instead and choose the option to save the irradiance map. Then, when the low res render is done, save it (so the map gets saved) then disable the Save irradiance Map option, and enable the Use Saved Irradiance Map. It will tremendously speed up the light calculations without hurting the lighting.
Another quick point about the Irradiance Map, is that it is for the whole scene regardless of camera angle. As long as you don't introduce new lights or objects, you could even animate a fly-through of your scene and the lighting should stay accurate.
A reminder about using Skylight and IL is to make sure that Light Through Transparency is enabled in the standard renderer and the GI (IL) renderer. Not having both enabled has been one of the biggest problems new users have had with it over the years. I'm including myself in that statement as well.
One can 'bake' an irradiance map in the render panel and save the irradiance file. This is helpful if one is still tweaking the scene as 3D adventurers tend to do. :)
Do you mean, Show Photon Map? Or is it more like what I was talking about above? Or is it perhaps an option n C8 and later?
So are you two saying to set it to "One for all frames"? Or is there a feature that neither of you are mentioning that allows us to save out the irradiance map, and use the 'load' function?
An animation that would have moving objects or changing lighting would in theory need to have a new map per frame. I have never animated with GI, but I understand that there can be flickering caused by the different maps. I have also heard of people that render their GI scene with the single, static map, and composite the moving elements into it, in post production. The manual also says that you can get some interesting results using a static map and animated objects or lights in your scene.
As far as I know, an Irradiance map cannot be treated as an image sequence.
Also, remember that the Irradiance map encompasses the whole scene according to the manual. This means that you can render from any angle, or animate your camera and the lighting will stay accurate. It's when you introduce animated elements such as moving objects and changing lights, that the irradiance values would change, but since it's a static map, irradiance and shadows won't change to match the movements or changes in lighting.
...adding to above replies...
In the render room , the Global Illumination mutli-pass element in the output tab is the same as an irradiance map. This can be used for image sequences in post editing programs if needed. The features, 'One for all frames(static scenes)' and 'Use saved map:' are the same thing except that one can save the map as a file for later use(Pro version).
The irradiance map only shows the diffuse part of indirect lighting. It won't show light reflected from mirror type shader or specular shiny sources. To get these light bounces, Caustics needs to be checked.
In my experience, the main increases in render time using indirect lighting come from the 'Photon Map accuracy'. If you are doing test renders, set this to 0.
Since tbwoq mentioned caustics, I'll throw this out there:
#1 Caustics isn't a real world simulation. Maybe because objects aren't truly volumetric. So trying to simulate light passing through a prism won't bend or refract as light does in the real world when shining through a prism.
#2 A white light in Carrara can't break into component colors when refracted through a prism as it would in the real world, because it isn't made up of all visible light in the spectrum. It's just a white color chip.
However you can make a white light in Carrara that will break apart by creating a light, and setting the brightness value to 33, then duplicate it two times so that you end up with three lights in exactly the same position. Now, make one light red, one light green and one light blue. The three together will create a light source that looks white and the cumulative brightness will be 99%. If you use Caustics and shine it through a refractive object, you'll get the look of light breaking apart into rainbow hues. It's not real-world physically accurate, but is a pretty cool approximation.
Both of you... thanks. Those are nice to know.
Reading the new edition of Jeremy Birn's Lighting and Rendering book as we speak. Half way through chapter three. Excellent book! It's refreshing to know that I've been using a lot of his techniques for some time now, and it's likely due to catching advice from people like you guys! :)
you are a genius :)
Wouldn't it make sense to be using the 64 bit version of Carrara,.. on a 64 bit OS (you should have both versions in your account)
32 bit applications (and OS's) are limited in how much ram they can access.
Hope it helps :)