Luxus Plugin or Carrara Never Finishes Rendering????
LinkRS
Posts: 168
Greetings Folks,
I just purchased and installed Luxus for Carrara (due to the Cyber-Monday sale), and was playing around with it. I tried the default scene installed with Luxrenderr, the sphere as indicated in the setup guide PDF, and finally one of my saved Carrara scenes. However in all cases, I ended up stopping the render manually as it never seems to finish? It just renders it over, and over, and over and over, and the log reports:"Writing Tonemapped PNG image to file 'C:\Users\Rich Selmon\Documents\Luxus\luxout.png'". I have let the render run for over an hour, and even the test sphere does the same thing. Does Luxus take hours to render, or is there something wrong? I am using the OpenCL version of Luxrender if it matters. Thanks!
Rich S.
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Comments
Yup :-) that is working as intended. It just keeps running forever. Crazy, huh?
I think there is actually a way to limit the render time, in the LuxRender interface… :red: I am not familiar enough to remember where...
"Over an hour" is usually just about enough to tell if the render is probably going to come out OK with no shadows or converted materials seriously misbehaving. It's a totally different type of render engine, using much closer to the actual physical behaviour of actual light rays bouncing among actual solid (or not) objects. Letting it run overnight is normal, even longer is not unusual.
The thing to watch for in LuxRender is the image quality, measured in "samples per pixel". Once you have a looks-good-enough render, you stop it and save your pretty picture. There is a way of defining a certain quality setting as a stop point, so you don't have to hover over your computer waiting for it to get there, but I don't know how that's done in Carrara; in DAZ|Studio it's done with a Render Settings parameter.
Yes, the default behaviour is to run until stopped, you will have seen that it produces a noisy version of your image very quickly and then the more it runs, the noise is reduced. Run it until the noise is imperceptible and then save the image. You can set a preset limit, this is particularly useful if you are mad enough to try to render animation frames with it, the way to set this in Carrara is to use the "Halt SPP" parameter under the Luxus render settings panel. A value of 1000 samples per pixel (SPP) is generally thought to be a reasonable threshold for a good quality (ie. relatively noise-free) render, but this can depend a lot on your lighting. I have had some that look great with "just" a few hundred, and some that still look a bit noisy with several thousand, especially where a lot of the light is bounced rather than direct.
The Luxrender interface allows you to "paint" using the Refine Brush to prioritise certain areas of your image, so if you find particular areas which have noise or "fireflies" (unusually bright pixels), you can specify that the render engine concentrate on these, which can help get a noiseless image more quickly. And of course you can interactively adjust exposure and light intensity of each light source to balance your image to perfection while it is rendering, which is great!
I know this is off topic,but, how often will LuxRender render until there is no more noise, I just bought Luxus last night but haven't installed it yet, but I do have Reality, and it seems no matter how long I let it render, there's still noise looks grainy
In theory, any scene will render until there is no visible noise if you give it long enough. A lot depends on the lighting, although surface properties play their part too. Matte surfaces will "settle" quicker than specular or reflective surfaces, and beware of setting reflection or specular too high. Where possible use direct lighting rather than relying excessively on bounced / indirect light. Mesh lights are probably the best light source to use for faster results. In general you can probably use fewer lights than you are used to, and avoid having too many lights in your scene. These are just some general guidelines. As you get relatively fast feedback on your image, you can fairly quickly spot areas of your image which might be a problem. You can either go back in and change the lighting or surfaces to help this, or use the refine brush to focus the renderer's attention on those areas.
As a rule of thumb, 1000 Samples per Pixel (SPP) should in most cases give a pretty noise-free render, although as I said above, it is sometimes higher or lower depending on the image. The issue is that it is a game of diminishing returns - you need to double the render time to halve the amount of noise. So if the noise in an image is N after an hour, it will be N/2 after 2 hours, N/4 after 4 hours, N/8 after 8 hours etc. If you have quite a noisy image to begin with, I think you can see that you could end up needing to run for a very long time to completely get rid of visible noise. Using the above strategies will help - as will a faster computer! I have used Luxrender a lot more since upgrading as the render times were significantly reduced.
what about animations? how con I be sure that I won't get noisy results?
even the sample file gave me a noisy result after 2 (!) hours.
Unless you have a scene that renders to a low noise state very quickly, I wouldn't even think of doing an animation in Luxrender. Stick to Carrara instead - even in Carrara you may have to make compromises to get it to render frames at a reasonable speed, but that is the compromise that 3D artists have lived with for decades.
As Phil said above. To add to that, to speed up render times for animations, your best bet is to learn how to simulate GI. Even a fairly complex light rig is going to render much faster than GI.
Even professional studios simulate GI due to the time hit when rendering, and these guys have hundreds or thousands of computers in their render farms cranking away on each shot.
This composite is just Carrara's standard renderer. I took some reference video and tried to match the real world lighting as best I could, taking into account reflected light from the ground and atmosphere.
http://youtu.be/_8puXTRXt7Y
This one was a little harder to light than it would appear at first glance. It helps that most people aren't really paying attention to the lighting per se. ;-)
http://youtu.be/nkWBRuJlQhA
Hi Everyone,
Thanks soooo much for the help. This is one of the most newbie friendly forums I have ever been a part of. I actually let one of the test renders hit 1000 samples, and it really didn't look less noisy than it did at 300 samples. However, I did not attempt to use any of the Luxus shaders or materials, and jus the shaders I had applied when I built it for Carrara. Interestingly enough, the render did not show the background at all, and it rendered black. The original is using a Realistic Sky, and a Carrara terrain for the ground.
Based on this info, I now have the impression that Luxrender is probably not a good "general" renderer due to the length of time. Is it better for certain types of renders, or perhaps just something to do for a final render before you publish it? Thanks!
Rich S.
What are you using for your lighting? Carrara's Realistic Sky does not convert to Lux, you need to use Lux SunSky2 instead, you can then set the direction of the sun and a few parameters with this. My guess is that you have insufficient lighting in your scene.
That mention of sky lighting is a good point — in D|S at least, I've always set up either a sky light or a few mesh lights before running a Luxus render, and I assume it would be similar in Carrara. The materials and lights in an existing scene might be automagically converted fairly well in many cases, but some things just have to be set up manually before hitting the render button.