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A Ray-Tracing Pioneer Explains How He Stumbled into Global Illumination

192 points by mariuz 8y ago

deleted 8y ago
[deleted]
dmritard96 8y ago
Would absolutely pay up if I could get realtime raytracing for Fusion360 (Industrial/Mechanical Design software). Waiting for renders to bake only to find out that the lighting needs to be adjusted slightly can be frustratingly slow.
- deleted 8y ago
  [deleted]
- pasta 8y ago
  I don't know if they will ever integrate this, but that's what I like about path tracing. Even on slow computers you will get a real time photorealistic result. You will have to wait long before all noise is gone but you will notice lighting problems in a sec.
- gt_ 8y ago
  I thought KeyShot had a quick plugin for that. I would be surprised if V-Ray for GPU doesn’t becomes available for Fusion 360 before long. I can’t honestly claim to know much about Fusion 360 but I do know the CAD folks love it. Octane or Redshift is what you’re really after but they are more boutique companies so it’s probably unlikely.
- semi-extrinsic 8y ago
  Hmm, IIRC Inventor does realtime raytracing, with first image after ~10 seconds and production quality images after a couple of minutes (this was on a XPS 15 laptop with the GTX 960M GPU). My guess is that it's one of the features Autodesk doesn't want to put in Fusion360 so they retain a market for the more expensive Inventor.
  - StavrosK 8y ago
    Ten seconds is hardly real-time, that's how long Fusion takes too. You can't easily adjust the camera view when you have to wait ten seconds between adjustments. That said, I think Fusion shows you a really low resolution image in real time, if I remember correctly.
  - GuB-42 8y ago
    I don't think we can call it real-time below 6 FPS (0.17s). That's the framerate of cheap anime. And the goal should be at least 30, which is a typical video game framerate. The only examples I have where real-time raytracing is used are demoscene productions where shapes are defined using simple mathematical primitives. (see the 4k intros "absolute territory" and "zetsubo", both from prismbeings for example).
- Nae3Au5x 8y ago
  Most renderers support near-realtime preview. If fusion360 doesn't maybe write a script that watches for file changes, converts the CAD data into whatever your renderer of choice takes as input and then display in preview mode? Maya+Vray spits out a preview within seconds on my machine.
  - StavrosK 8y ago
    Unfortunately, there is no file. Fusion has this monstrosity where everything is stored in Autodesk servers. I don't know if you can export the files, but saving uploads them to Autodesk.
  - dmritard96 8y ago
    Do you have some examples you can link to of something you have rendered in a few seconds? Fusion has some sort of simpler preview, my guess is that its some closed form lighting solver and in certain contexts it can look ok but for photorealism of a scene, its nowhere close. I see a decent number of suggestions that people have really fast renders but I'm suspicious that we are talking about very different things. Here is what I am typically rendering: -Full screen on a 15" retina MBP -Ray Traced -In additional to the product, whole rooms/scenes that contextualize including 3D textured woods, books with Decals that are wrapped, elements of various opacity/transmissiveness, objects with some luminance, etc. - Some objects with very high numbers of points (there is a technical name I'm forgetting), but essentially, circles render with enough polygons to not appear as a collection of lots of small/slightly noticeable line segments
- dtf 8y ago
  Rhino3D integrated Blender’s open-source Cycles renderer. https://github.com/mcneel/RhinoCycles https://github.com/mcneel/RhinoCycles
fizixer 8y ago
It's a good historical anecdote about making progress in computer graphics, but ray tracing is largely an obsolete method, since 'path tracing', the method that stochastically solves the rendering equation by James Kajiya, can do global illumination way more realistically (in principle, it can give true realism). In fact ray tracing cannot do global illuminuation and any ray tracing engine that does that is essentially including a hack on top of its core ray tracer. You can even look at the images shared in the article and see for yourself as to how realistic or unrealistic they look. Path tracing is not good for 'real-time' computer graphics at the moment, because GPUs need to be still more computationally powerful, though I think 2018 or 2019 is the year we'll have the first computer game based on path tracing. On the other hand, ray tracing is already easily doable in GPUs, since it's computationally less expensive than path tracing, but IMO, no one is interested in it since games either want maximum possible realism, or if they want "cartoonish graphics," they want a certain look, not the look imposed on them by the renderer, and ray tracing cannot give enough control to produce any look the artist has in mind (without massive hacks). EDIT: I just realized, nVidia is promoting ray-tracing as the future of CG, and everything they're describing are actually qualities/features of path tracing and have nothing to do with ray tracing (except for this historical article). I'm seriously perplexed. Maybe nVidia's marking department thought the word 'ray tracing' is more catchy, and more people know about it, so they should use it everywhere. It's common knowledge in CG research community that ray tracing cannot do global illumination. EDIT 2: Another possible reason is that if they start mentioning path tracing, people will start asking questions about the difference between ray tracing and path tracing, and sales people don't want to get into that. It's a bit like calling LCD displays thin CRTs out of fear that if they mention LCD, people would start asking about the difference between CRT and LCD.
- deleted 8y ago
  [deleted]
- valine 8y ago
  The thing about path tracing that isn’t mentioned often is that it can take anywhere from 1/60th of second to 16 hours to render a single frame. The images that people associate with path tracers are usually of the 16 hour variety. Just because a game could technically use a path tracer as it’s render engine doesn’t mean it will provide any visual benefit over traditional realtime rendering.
bhouston 8y ago
Papers mentioned in the article: "An Improved Illumination Model for Shaded Display" (1978): http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.107.3997&rep=rep1&type=pdf http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.107... "A 3-Dimensional Representation for Fast Rendering of Complex Scenes" (1980): http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.133.6937&rep=rep1&type=pdf http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.133...
rollulus 8y ago
I used to be active in computer graphics. Great to see an article by Whitted himself. A bit of trivia: I think _the_ pioneer in the field of ray-tracing is Albrecht Dürer [1] who ray traced by hand in the 16th century. [1]: https://www.researchgate.net/figure/Man-drawing-a-lute-by-Albrecht-Duerer-1525-In-this-drawing-Duerer-illustrates-a_fig16_312605716 https://www.researchgate.net/figure/Man-drawing-a-lute-by-Al...
- dahart 8y ago
  That immediately reminded me of "Tim's Vermeer", have you seen it? Software guy Tim hypothesizes that Vermeer was tracing rays using an optical setup without strings, maybe vaguely similar to Dürer's. He sets out to recreate the device and Vermeer's painting's. It's a wonderful project.
  - rollulus 8y ago
    I haven't seen it, but I just watched the trailer. Looks like an awesome documentary, thanks!
- brobdingnagians 8y ago
  It always amazes me how things we think of as high-tech modern innovations were often known by people a long time ago. There have always been ingenious people, and sometimes they achieved things long before I would have thought it possible. Archimedes almost invented calculus thousands of years ago, and the Greeks knew the distance to the moon and sun[1]. A little ingenuity can figure something out from simple principles; always a reminder that each person in history were living, breathing, thinking people as real as you and I, with a unique viewpoint and achievements. 1. [https://en.wikipedia.org/wiki/On_the_Sizes_and_Distances_(Aristarchus) https://en.wikipedia.org/wiki/On_the_Sizes_and_Distances_(Ar...]
- Keyframe 8y ago
  This is both funny and awful at the same time. I've been in graphics forever, and his name alone demands respect. He's so much of a corner stone, since forever, that it never occurred to me that the guy might still be alive, let alone working at Nvidia Research! Nvidia Research seems to have scooped up all of the legends.
Keyframe 8y ago
Tracing ray from camera towards light source is called Whitted raytracing - author of the text is J. Turner Whitted.

192 points by mariuz 8y ago

deleted 8y ago

[deleted]

Would absolutely pay up if I could get realtime raytracing for Fusion360 (Industrial/Mechanical Design software). Waiting for renders to bake only to find out that the lighting needs to be adjusted slightly can be frustratingly slow.

deleted 8y ago
[deleted]
pasta 8y ago
I don't know if they will ever integrate this, but that's what I like about path tracing. Even on slow computers you will get a real time photorealistic result. You will have to wait long before all noise is gone but you will notice lighting problems in a sec.
gt_ 8y ago
I thought KeyShot had a quick plugin for that. I would be surprised if V-Ray for GPU doesn’t becomes available for Fusion 360 before long. I can’t honestly claim to know much about Fusion 360 but I do know the CAD folks love it. Octane or Redshift is what you’re really after but they are more boutique companies so it’s probably unlikely.
semi-extrinsic 8y ago
Hmm, IIRC Inventor does realtime raytracing, with first image after ~10 seconds and production quality images after a couple of minutes (this was on a XPS 15 laptop with the GTX 960M GPU). My guess is that it's one of the features Autodesk doesn't want to put in Fusion360 so they retain a market for the more expensive Inventor.
- StavrosK 8y ago
  Ten seconds is hardly real-time, that's how long Fusion takes too. You can't easily adjust the camera view when you have to wait ten seconds between adjustments. That said, I think Fusion shows you a really low resolution image in real time, if I remember correctly.
- GuB-42 8y ago
  I don't think we can call it real-time below 6 FPS (0.17s). That's the framerate of cheap anime. And the goal should be at least 30, which is a typical video game framerate. The only examples I have where real-time raytracing is used are demoscene productions where shapes are defined using simple mathematical primitives. (see the 4k intros "absolute territory" and "zetsubo", both from prismbeings for example).
Nae3Au5x 8y ago
Most renderers support near-realtime preview. If fusion360 doesn't maybe write a script that watches for file changes, converts the CAD data into whatever your renderer of choice takes as input and then display in preview mode? Maya+Vray spits out a preview within seconds on my machine.
- StavrosK 8y ago
  Unfortunately, there is no file. Fusion has this monstrosity where everything is stored in Autodesk servers. I don't know if you can export the files, but saving uploads them to Autodesk.
- dmritard96 8y ago
  Do you have some examples you can link to of something you have rendered in a few seconds? Fusion has some sort of simpler preview, my guess is that its some closed form lighting solver and in certain contexts it can look ok but for photorealism of a scene, its nowhere close. I see a decent number of suggestions that people have really fast renders but I'm suspicious that we are talking about very different things. Here is what I am typically rendering: -Full screen on a 15" retina MBP -Ray Traced -In additional to the product, whole rooms/scenes that contextualize including 3D textured woods, books with Decals that are wrapped, elements of various opacity/transmissiveness, objects with some luminance, etc. - Some objects with very high numbers of points (there is a technical name I'm forgetting), but essentially, circles render with enough polygons to not appear as a collection of lots of small/slightly noticeable line segments
dtf 8y ago
Rhino3D integrated Blender’s open-source Cycles renderer. https://github.com/mcneel/RhinoCycles https://github.com/mcneel/RhinoCycles

fizixer 8y ago

It's a good historical anecdote about making progress in computer graphics, but ray tracing is largely an obsolete method, since 'path tracing', the method that stochastically solves the rendering equation by James Kajiya, can do global illumination way more realistically (in principle, it can give true realism). In fact ray tracing cannot do global illuminuation and any ray tracing engine that does that is essentially including a hack on top of its core ray tracer. You can even look at the images shared in the article and see for yourself as to how realistic or unrealistic they look. Path tracing is not good for 'real-time' computer graphics at the moment, because GPUs need to be still more computationally powerful, though I think 2018 or 2019 is the year we'll have the first computer game based on path tracing. On the other hand, ray tracing is already easily doable in GPUs, since it's computationally less expensive than path tracing, but IMO, no one is interested in it since games either want maximum possible realism, or if they want "cartoonish graphics," they want a certain look, not the look imposed on them by the renderer, and ray tracing cannot give enough control to produce any look the artist has in mind (without massive hacks). EDIT: I just realized, nVidia is promoting ray-tracing as the future of CG, and everything they're describing are actually qualities/features of path tracing and have nothing to do with ray tracing (except for this historical article). I'm seriously perplexed. Maybe nVidia's marking department thought the word 'ray tracing' is more catchy, and more people know about it, so they should use it everywhere. It's common knowledge in CG research community that ray tracing cannot do global illumination. EDIT 2: Another possible reason is that if they start mentioning path tracing, people will start asking questions about the difference between ray tracing and path tracing, and sales people don't want to get into that. It's a bit like calling LCD displays thin CRTs out of fear that if they mention LCD, people would start asking about the difference between CRT and LCD.

deleted 8y ago
[deleted]
valine 8y ago
The thing about path tracing that isn’t mentioned often is that it can take anywhere from 1/60th of second to 16 hours to render a single frame. The images that people associate with path tracers are usually of the 16 hour variety. Just because a game could technically use a path tracer as it’s render engine doesn’t mean it will provide any visual benefit over traditional realtime rendering.

bhouston 8y ago

Papers mentioned in the article: "An Improved Illumination Model for Shaded Display" (1978): http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.107.3997&rep=rep1&type=pdf http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.107... "A 3-Dimensional Representation for Fast Rendering of Complex Scenes" (1980): http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.133.6937&rep=rep1&type=pdf http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.133...

rollulus 8y ago

I used to be active in computer graphics. Great to see an article by Whitted himself. A bit of trivia: I think _the_ pioneer in the field of ray-tracing is Albrecht Dürer [1] who ray traced by hand in the 16th century. [1]: https://www.researchgate.net/figure/Man-drawing-a-lute-by-Albrecht-Duerer-1525-In-this-drawing-Duerer-illustrates-a_fig16_312605716 https://www.researchgate.net/figure/Man-drawing-a-lute-by-Al...

dahart 8y ago
That immediately reminded me of "Tim's Vermeer", have you seen it? Software guy Tim hypothesizes that Vermeer was tracing rays using an optical setup without strings, maybe vaguely similar to Dürer's. He sets out to recreate the device and Vermeer's painting's. It's a wonderful project.
- rollulus 8y ago
  I haven't seen it, but I just watched the trailer. Looks like an awesome documentary, thanks!
brobdingnagians 8y ago
It always amazes me how things we think of as high-tech modern innovations were often known by people a long time ago. There have always been ingenious people, and sometimes they achieved things long before I would have thought it possible. Archimedes almost invented calculus thousands of years ago, and the Greeks knew the distance to the moon and sun[1]. A little ingenuity can figure something out from simple principles; always a reminder that each person in history were living, breathing, thinking people as real as you and I, with a unique viewpoint and achievements. 1. [https://en.wikipedia.org/wiki/On_the_Sizes_and_Distances_(Aristarchus) https://en.wikipedia.org/wiki/On_the_Sizes_and_Distances_(Ar...]
Keyframe 8y ago
This is both funny and awful at the same time. I've been in graphics forever, and his name alone demands respect. He's so much of a corner stone, since forever, that it never occurred to me that the guy might still be alive, let alone working at Nvidia Research! Nvidia Research seems to have scooped up all of the legends.

Keyframe 8y ago

Tracing ray from camera towards light source is called Whitted raytracing - author of the text is J. Turner Whitted.