7 ms·

The Art of Rendering (2012)

96 points by tellarin 13y ago

Scene_Cast2 13y ago
Something I've been meaning to do for a while is to write an analytic renderer that evaluates the light equation. Basically, it would be a program that takes in analytic geometric data and spits out an equation (or a system of equations) that can be evaluated in Mathematica / Maxima. The runtime complexity would be horrible, but at least it would give mathematically perfect, noiseless results. Or a hybrid approach could work, too (get the equations, do a series approximation, sample the polynomial or whatever else you end up with). To anyone looking to get into graphics - I strongly recommend writing a toy scanline raytracer - it's a great learning experience.
- ykl 13y ago
  I have a feeling that this is one of those ideas that is going to be far far harder than you think it will be.
  - stevenschronk 13y ago
    I have been working on one and it's not that hard actually. The most difficult part has been creating the right data model.
  - Scene_Cast2 13y ago
    So far I've tried doing it on paper for a infinite plane with a single step and uniform lighting. I ended up with a scaled atan(x) as the function of light depending on the distance from the step. I haven't figured out how to handle complex occluding geometry in a nice way.
    - ykl 13y ago
      That's exactly what I mean; the simple sanity check case is easy, but once you start layering on things like complex geometry and surface models and volume data, the problem grows in difficulty absurdly quickly.
- cscheid 13y ago
  Unfortunately, ray tracing of general scenes is undecidable: http://www.cs.duke.edu/~reif/paper/tygar/raytracing.pdf http://www.cs.duke.edu/~reif/paper/tygar/raytracing.pdf
  - carterschonwald 13y ago
    The stochastic raytracing algorithms are "exact" if they're run long enough, right? (I know I've spoken to you and Edward about this stuff at length) Semirelatedly, do you think the Haskell Diagrams lib with its normals tricks would be a good pedagogical substrate for raytracing for general shapes? Seems like it would allow punting on how surfaces are represented Mebe.
KaiserPro 13y ago
Scott Metzger is a religion. His deity is Vray. Having worked with the haircut himself, he does do some wonderful things with mari/maya. He also requires super beefy machines.
Xcelerate 13y ago
Very good article! I remember I became obsessed with 3D rendering in high school 6 years ago and actually wrote a little photon mapper myself (I also remembering re-writing the Wikipedia article on photon mapping at one point). I always had the goal to turn it into something really useful but once college started that project kind of ground to a halt. Nowadays if I were to do it again, I'd just do Metropolis light sampling because I much prefer the unbiased nature of that global illumination solution than photon mapping's approximation (meaning if you average thousands of results from a MLS render it will converge on the exact solution to the rendering equation; this is not the case with photon mapping). I've always wondered though if someone has found a solution to the pinhole problem: imagine you have a scene that contains a box. Inside the box is a very bright light, and outside of the box it is pitch black. Your camera is pointing at the box. If you rendered the scene, your resulting image would be completely black. Now imagine you poke a small "pinhole" in the box. In real-life, your resulting image would be well-lit because of the very bright light now bleeding out of the box. But none of the rendering techniques I know of would be able to "find" this pinhole in a reasonable amount of time without manually provided additional information. Any rendering experts know the solution to this?
- ykl 13y ago
  Metropolis light transport with manifold exploration should be able to handle that case.
berkut 13y ago
And the followups to do with actual production renderers: http://www.fxguide.com/featured/the-state-of-rendering/ http://www.fxguide.com/featured/the-state-of-rendering/ http://www.fxguide.com/featured/the-state-of-rendering-part-2/ http://www.fxguide.com/featured/the-state-of-rendering-part-... What's interesting is how far Pixar's PRMan has fallen within 2-3 years, despite PRMan 19 (current in alpha) going to provide BDPT with vertex connection and merging (state of the art lighting equation). The problem is, despite providing the above, they're still getting some of the basics wrong, and Geometric lights still aren't being sampled correctly, in addition to: Even with fully raytraced (i.e. no REYES) setups in it, its instancing support is still fairly pathetic, and its texture paging support is shockingly bad, even with Pixar-proprietary pixar format for images. Once by far the dominant renderer in VFX, Arnold has come along and knocked PRMan off its perch (although Arnold still has a few issues as well).
- ykl 13y ago
  Similarly, watch Vray closely. I have a feeling that in the next few years, Corona is going to eat Vray's lunch much in the same way that Arnold is eating PRMan's right now.
  - berkut 13y ago
    Yeah, maybe, but Chaos Group seem to be fighting back a bit with Vray 3 (much faster MC GI and BDPT support)... - they still need to sort their GPU side of things out though... It's great that there's so much competition and so many renderers out there at the moment. This is partly due to the fact that it's not that difficult to write a "close to production" raytracer (ignoring asset paging, recursive procedural and curve support, which is where the big boys really shine).
    - psvx 13y ago
      Trust me, it's not _that_ simple :). (I'm working @ ChaosGroup on vray).
      - 13y ago
coldtea 13y ago
Are there any rendering tools that automate creating say tens or hundrends of Amazon AWS instances to partition the work for large animations?
- ykl 13y ago
  Considering that a single frame can require potentially hundreds of gigs of data at professional studios, the bottleneck with using AWS as a renderfarm isn't in provisioning instances but rather is in just sheer bandwidth.
Gregorein 13y ago
I wonder why they didn't mention the Cycles engine for Blender, even in it's early stages it already provides reliable power.
mrcactu5 13y ago
what is this considered image processing or 3d graphics? there seems to be a lot of math+physics involved which is great
- downer91 13y ago
  It's both. It's literally the transition phase from 3 dimensional models (vector-based curves, points, and polygons) to final pixel-based raster images. Rendering transforms the wireframe models into images. 3D graphics always involve a renderer of some kind. There are different classes of rendering. The kind that video games use are optimized for speed and interactivity, they are still rasterizing the 3D models into images, but the images are dumped to the video buffer and disposed of, with each new frame, at 30 frames per second. This article discusses renderers that are not concerned with speed or interactivity. The finished frames are retained and polished with compositing and photo editing software, including photoshop. In this case, the renderer is permitted to crunch numbers on a frame for minutes, hours or days, rather than 30 disposable frames per second.
cyberjunkie 13y ago
CGTalk (now CGsociety) doesn't seem as active and lush as it was back in 2002 - 2007 or so. Has everyone moved to some other community? Can anyone shed some light on other communities?

96 points by tellarin 13y ago

Something I've been meaning to do for a while is to write an analytic renderer that evaluates the light equation. Basically, it would be a program that takes in analytic geometric data and spits out an equation (or a system of equations) that can be evaluated in Mathematica / Maxima. The runtime complexity would be horrible, but at least it would give mathematically perfect, noiseless results. Or a hybrid approach could work, too (get the equations, do a series approximation, sample the polynomial or whatever else you end up with). To anyone looking to get into graphics - I strongly recommend writing a toy scanline raytracer - it's a great learning experience.

ykl 13y ago
I have a feeling that this is one of those ideas that is going to be far far harder than you think it will be.
- stevenschronk 13y ago
  I have been working on one and it's not that hard actually. The most difficult part has been creating the right data model.
- Scene_Cast2 13y ago
  So far I've tried doing it on paper for a infinite plane with a single step and uniform lighting. I ended up with a scaled atan(x) as the function of light depending on the distance from the step. I haven't figured out how to handle complex occluding geometry in a nice way.
  - ykl 13y ago
    That's exactly what I mean; the simple sanity check case is easy, but once you start layering on things like complex geometry and surface models and volume data, the problem grows in difficulty absurdly quickly.
cscheid 13y ago
Unfortunately, ray tracing of general scenes is undecidable: http://www.cs.duke.edu/~reif/paper/tygar/raytracing.pdf http://www.cs.duke.edu/~reif/paper/tygar/raytracing.pdf
- carterschonwald 13y ago
  The stochastic raytracing algorithms are "exact" if they're run long enough, right? (I know I've spoken to you and Edward about this stuff at length) Semirelatedly, do you think the Haskell Diagrams lib with its normals tricks would be a good pedagogical substrate for raytracing for general shapes? Seems like it would allow punting on how surfaces are represented Mebe.

KaiserPro 13y ago

Scott Metzger is a religion. His deity is Vray. Having worked with the haircut himself, he does do some wonderful things with mari/maya. He also requires super beefy machines.

Xcelerate 13y ago

Very good article! I remember I became obsessed with 3D rendering in high school 6 years ago and actually wrote a little photon mapper myself (I also remembering re-writing the Wikipedia article on photon mapping at one point). I always had the goal to turn it into something really useful but once college started that project kind of ground to a halt. Nowadays if I were to do it again, I'd just do Metropolis light sampling because I much prefer the unbiased nature of that global illumination solution than photon mapping's approximation (meaning if you average thousands of results from a MLS render it will converge on the exact solution to the rendering equation; this is not the case with photon mapping). I've always wondered though if someone has found a solution to the pinhole problem: imagine you have a scene that contains a box. Inside the box is a very bright light, and outside of the box it is pitch black. Your camera is pointing at the box. If you rendered the scene, your resulting image would be completely black. Now imagine you poke a small "pinhole" in the box. In real-life, your resulting image would be well-lit because of the very bright light now bleeding out of the box. But none of the rendering techniques I know of would be able to "find" this pinhole in a reasonable amount of time without manually provided additional information. Any rendering experts know the solution to this?

ykl 13y ago
Metropolis light transport with manifold exploration should be able to handle that case.

berkut 13y ago

And the followups to do with actual production renderers: http://www.fxguide.com/featured/the-state-of-rendering/ http://www.fxguide.com/featured/the-state-of-rendering/ http://www.fxguide.com/featured/the-state-of-rendering-part-2/ http://www.fxguide.com/featured/the-state-of-rendering-part-... What's interesting is how far Pixar's PRMan has fallen within 2-3 years, despite PRMan 19 (current in alpha) going to provide BDPT with vertex connection and merging (state of the art lighting equation). The problem is, despite providing the above, they're still getting some of the basics wrong, and Geometric lights still aren't being sampled correctly, in addition to: Even with fully raytraced (i.e. no REYES) setups in it, its instancing support is still fairly pathetic, and its texture paging support is shockingly bad, even with Pixar-proprietary pixar format for images. Once by far the dominant renderer in VFX, Arnold has come along and knocked PRMan off its perch (although Arnold still has a few issues as well).

ykl 13y ago
Similarly, watch Vray closely. I have a feeling that in the next few years, Corona is going to eat Vray's lunch much in the same way that Arnold is eating PRMan's right now.
- berkut 13y ago
  Yeah, maybe, but Chaos Group seem to be fighting back a bit with Vray 3 (much faster MC GI and BDPT support)... - they still need to sort their GPU side of things out though... It's great that there's so much competition and so many renderers out there at the moment. This is partly due to the fact that it's not that difficult to write a "close to production" raytracer (ignoring asset paging, recursive procedural and curve support, which is where the big boys really shine).
  - psvx 13y ago
    Trust me, it's not _that_ simple :). (I'm working @ ChaosGroup on vray).
    - 13y ago

coldtea 13y ago

Are there any rendering tools that automate creating say tens or hundrends of Amazon AWS instances to partition the work for large animations?

ykl 13y ago
Considering that a single frame can require potentially hundreds of gigs of data at professional studios, the bottleneck with using AWS as a renderfarm isn't in provisioning instances but rather is in just sheer bandwidth.

Gregorein 13y ago

I wonder why they didn't mention the Cycles engine for Blender, even in it's early stages it already provides reliable power.

mrcactu5 13y ago

what is this considered image processing or 3d graphics? there seems to be a lot of math+physics involved which is great

downer91 13y ago
It's both. It's literally the transition phase from 3 dimensional models (vector-based curves, points, and polygons) to final pixel-based raster images. Rendering transforms the wireframe models into images. 3D graphics always involve a renderer of some kind. There are different classes of rendering. The kind that video games use are optimized for speed and interactivity, they are still rasterizing the 3D models into images, but the images are dumped to the video buffer and disposed of, with each new frame, at 30 frames per second. This article discusses renderers that are not concerned with speed or interactivity. The finished frames are retained and polished with compositing and photo editing software, including photoshop. In this case, the renderer is permitted to crunch numbers on a frame for minutes, hours or days, rather than 30 disposable frames per second.

cyberjunkie 13y ago

CGTalk (now CGsociety) doesn't seem as active and lush as it was back in 2002 - 2007 or so. Has everyone moved to some other community? Can anyone shed some light on other communities?