Today we have a new add-in board coprocessor in town. Caustic Graphics has announced their CausticOne hardware and CausticGL API which will enable hardware accelerated raytracing. We are reminded of Ageia's venture into dedicated hardware for physics, but Caustic Graphics seems to be taking a more balanced approach to bringing their hardware to market. The goal is to start at the top where cost is no object and get developers interested in and working with their hardware before they bring it to the end user.

Pixar and other studios that make heavy use of computer generated animation for films tend to have render farms that can take seconds, minutes or even hours to render. With full length films lasting about 150000 frames (plus or minus), that time really adds up. Those that need to render one frame as near reality as possible (say car designers doing preliminary visualization of a new model) can kick off rendering jobs that take days to complete. These guys put tons of cash into their computer systems. Time is money and if Caustic can save these guys more time than it would cost them to buy the hardware and port their software, then Caustic will do well.

The long term goals might have something to do with gaming, but we definitely aren't looking at that option right now. By trying to penetrate the market at the back end like this, Caustic Graphics may avoid the pitfalls we saw Aegia run into. Of course, at this point it is unclear whether or not the end user will even need a dedicated raytracing card by the time the hardware makes it to market. With current GPUs getting faster all the time, CPUs becoming increasingly parallel, and Larrabee on the horizon, there are quite a number of factors that will affect the viability of a part like this in consumer space.

Regardless, Caustic Graphics is here and ready to start making an impact. Their SDK should be available to developers today, with hardware soon to follow. Before we take a deeper look at what Caustic Graphics is offering, let's talk a little bit about the differences between rasterization (what current GPUs do) and raytracing (what the Caustic Graphics hardware will accelerate).

What is Raytracing?


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  • ssj4Gogeta - Monday, April 20, 2009 - link

    I'm no pro, but from what I know the main difference is that things like shadows, refractions and reflections render MUCH better. This is because in raytracing you also use secondary rays. So the rays reflected off/refracted from a surface can affect the color of other nearby surfaces, producing shadows, reflections, etc. In ray tracing you do it just like nature does it in real world (in reverse of that, but that doesn't affect the outcome). In rasterization, you need to manually program for producing shadows, reflections, etc. and so they are mostly just approximations.

    Another advantage of ray tracing is that programmers don't need to work that hard - things which may take you hundreds of lines of code in rasterization, only take 10 lines in ray tracing.

    Compare this to 3D vs 2D rendering of a 3D cube. Suppose you need to render the cube as the camera circles around it. If you're doing it in 3D, you just render it in 3D, flatten the image and display it. Now if you're using 2D, but you want to create the effect of 3D, you don't have to render a cube - you need to directly render how the flattened image would look. That is, you need to take into account the 3D distortion due to perspective/depth and you need to make the edges of the cube oblique accordingly, you need to make the part of the cube that is farther look farther by rendering it smaller than the face of the cube that is closer to the camera. A lot of work for the programmer, and needless to say, it won't be very accurate. Well in this case it may be accurate as it's just a cube with straight edges, and so you can easily calculate things. But not in the case of a complex object.

    Same way, rasterization at best can offer approximations of phenomena like refraction etc., how close they are depend on the programmer.

    Check this rendered pic to see what ray tracing can deliver:">

    Note: I'm not a graphics programmer but this is how I understand it. Please correct me where I'm wrong.
  • AmbroseAthan - Wednesday, April 22, 2009 - link

    That picture is a ray-traced rendering?! It looks like a photograph! Someone put in a lot of time and crunching power on that one. Reply
  • JimmiG - Monday, April 20, 2009 - link

    I'm also wondering about #2 - is Raytracing really "better", or just "different"?

    Back in the 90's I used to be really impressed with the quality of raytraced animations and pictures, with their shiny, reflective objects, realistic water, lighting, soft shadows etc. However back then the capabilities of "3d accelerators" were very limited - 3d games used simple models, "flat" lighting models with no shadows and only one light source, and blurry textures without any shader effects like bumps, parallax maps, reflections etc. Today it seems the latest 3d engines already do everything in realtime that you needed raytracing and many minutes/hours per scene to do in the past.
  • jimhsu - Monday, April 20, 2009 - link

    Someone correct me, but i think it is not that raytracing "looks" better, but because it is closer to a physical description of light (only in inverse), effects such as ambient occlusion, caustics, and other shiny things can be implemented in a relatively straightforward manner in a physically correct manner, while rasterization requires the use of shaders to "emulate" reality. These approximations are often complicated to program and implement, even though they achieve nearly the same effect. Reply
  • DerekWilson - Tuesday, April 21, 2009 - link

    this is sort of true ... it's possible to write shaders for a rasterizer that do everything a raytracer does. But in addition to the code complexity in a z-buffer based rasterizer you end up with performance disadvantages.

    At the point where you properly and accurately emulate raytracing with a rasterizer you need to start generating all kinds of dynamic environment maps every frame for every object. treating objects as light sources and doing real time radiosity for rasterization (which can be done as well) is also difficult. To get an image that is as physically accurate as raytracing, rasterization (at this point with todays technology) would be slower even using a GPU designed for rasterization.

    Honestly, there are some things that rasterization can approximate well enough that we don't notice the difference, and I think for a long time to come we'll still see rasterization as the main vehicle for realtime graphics. I think we'll start to see raytracing come in as a secondary tool to augment rasterization and add effects that are tough to achieve otherwise.
  • lopri - Tuesday, April 21, 2009 - link

    I think I am learning more abou raytracing from this article and comments than anywhere else to date. Thank you for excellent explanations and analogies! Reply
  • jimhsu - Monday, April 20, 2009 - link

    An analogy for math majors would probably be trying to solve a function analytically (i.e. rules of calculus) vs. numerically (i.e. Newton's Method, Euler, etc). The numerical result is often close to the analytical result, but intuitively the analytical result is the "right" way to do the problem, except when it is infeasible (we have something that we can't integrate). Reply
  • Einy0 - Monday, April 20, 2009 - link

    This may actually help Larrabee gain ground. An alternative to do realtime raytracing. Then again Larrabee may help this gain ground as Larrabee will be do both rasterizing and raytracing.
    I'm surpirsed they can make anything worth buying with FPGAs. I guess FPGAs have come a long way. I'd love to get some specifics on the underlying architecture.
    Bad timing considering the global economy etc...
  • ifkopifko - Tuesday, April 21, 2009 - link

    lol... real-time raytracing? Keep dreaming. :-D Something like that is far far in the future. Reply
  • Sivar - Tuesday, April 21, 2009 - link

    There have been assembly language demos from the 4k scene which have done realtime ratracing since the late 90's. In software. On a Pentium MMX.
    They aren't quite what I'd call Pixar-quality, but it's far from impossible.


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