In the motorcycling world there is a saying: “there is no replacement for displacement.”

Displacement is the size of an engine, a bigger displacement means a faster engine. That saying highlights that you can try to put a better carburetor or improve the coils, spark plug, and air filter, and all those things are nice, but they cannot hold a candle to sheer size. If you want to go faster you need to get more gasoline in the motor and to do so the motor has to be bigger.

Sometimes I hear people complaining about LuxRender’s speed and that surprises me quite a bit. I don’t think that everybody realizes how fast LuxRender really is. The fact is that often LuxRender is made to run on limited machines and that is not an issue of software but of hardware, aka the displacement that we just mentioned. This is similar to trying to run a car race with a Prius. I love energy efficient cars but if you need to haul ass then you need displacement.

When we look at the evolution of CPUs, the old model focused on single-core processors that were made to go faster every 12 or 18 months. That model lasted from the early 80’s to the early 2000’s. During that period processors became faster and faster and software was strictly sequential:  instructions were executed one at a time. In the past few years a shift has happened and I’m not sure that everyone is aware of this. Processor speed has not gone up much. We inched up a little bit but the jumps of the past are gone and are not coming back any time soon. My MacPro, a 2009 model, has 8-core Xeon processors at 2.26Ghz and this is a five year old machine now.  Five years later the top speed of Intel CPUs is at a mere 3.9Ghz. We are not going to see a 8Ghz or 10Ghz processor the next year or in two years. On the other hand, processors started gaining multiple cores and today it’s common to have PCs with 8 cores or even more.If you are running with anything less than eight cores, in 2014, you are severely penalizing your performance. Dual core or quad-core machines are simply not up to today’s challenges when it comes to computer graphics.

LuxRender is a highly-parallelized program. It will take any amount of cores in your machine and push them to the max with the result of increasing rendering speed dramatically. This model, of highly parallelized execution, is where we are going. More and more software is designed to work in that way.

My friend Cirstyn, who is the head of Northern Studios, and a well-established 3D artist doing advertising work for AMD and other high-profile companies, told me recently a funny story. When she first heard of Reality in 2010 she discarded it as being bogus. The reason was that she saw the promos for the product and concluded that it was impossible for the software to do what it claimed in the time claimed to make those images. You see, the time was just too short for her to be believable. This is from an 3D expert used to run program like 3D Studio Max in conjunction with multiple renderers. She is acutely aware of the time that is needed to render good images. Brutal deadlines for multi-million dollar companies made her understand how software renders and at what level.

But even with her experience the real catalyst for her conclusion was a test that she had made with Studio’s own renderer, the very respectable 3Delight. The following image shows a simple scene that she tried to render back then. The scene has a single figure with armor and some props. There is not much going on but the settings that Cirstyn used were dialed to the maximum. After 8 hours the image was processed only at 21%, basically a fifth of the time needed to complete it. This was with a quad-core i7 at 2.93Mhz with hyper-threading. LuxRender runs 8 threads of concurrent rendering on that processor. It would require 3Delight 40 hours to finish it and the image doesn’t look nearly as realistic as what you can obtain with Reality and LuxRender. Her conclusion was that my claims were false. I love that.

Studio render times

Obviously Cirstyn decided to try Reality anyway and realized that LuxRender was actually using her multi-core hardware much better than many other programs. LuxRender is in fact a very, very efficient program. Several people told me how they find LuxRender noticeably faster than Vue’s renderer, for example.

LuxRender emphasis is on physical accuracy. Of course it’s possible to render similar scenes faster than what LuxRender does but that  is done by cutting corners and by avoiding accuracy. The point here is that LuxRender gives us incredible physical accuracy and fast rendering via use of multiple cores. When we render a scene in Studio or Poser generally we use the default settings. Those settings are good for general use and they have been tuned to provide a very fast response. They are not designed for ultra-accuracy or for photo-realism. When an expert like Cirstyn takes the renderer in those programs and cranks up the volume to 11 the response is quite different. In fact LuxRender looks downright fast in comparison with the above scenario and it brings a level of realism that those other programs just don’t have.

Let’s also remember that Lux scales up very nicely and consistently. For example, when we add more figures or complex objects, like detailed hair, the speed of the renderer is impacted lightly. When we do the same in 3Delight or Firefly the speed drops dramatically. If we keep rendering a figure with some clothing then we are underutilizing what LuxRender can do. Throw a full environment, multiple figures, multiple lights, reflections and all the elements that bring an image alive and Lux will chug along nicely while other renderers will show limitations.

Here is another image that Cirstyn tried to render with multiple objects:

Studio render speed 2

After more than 5 hours the render is still at 0%. We are well aware that on a system capable of 8 threads, Lux would have shown remarkable progress after that time.

So, it’s important that we compare oranges with oranges, and when we do that we see that LuxRender is a fast renderer that provides accuracy that you can only see on program that cost anywhere between $800 to $1000+.  Best of all, it completely free. Yes, you can have your cake and eat it too.

Happy rendering.


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