4 ms·

Raytracing is just one tool in a bag of necessary algorithms. For instance, there's no obvious way to extend raytracing to offer indirect lighting—all existing

by duaneb 13y ago

Raytracing is just one tool in a bag of necessary algorithms. For instance, there's no obvious way to extend raytracing to offer indirect lighting—all existing algorithms offer some form of tradeoff. Furthermore, many effects are flat out a pain to render with raytracing: displacement mapping, subsurface scattering, anti-aliasing, and scenes where both speed of rendering and dynamic geometry are needed. All of those require substantial thought and are non-trivial to implement. And don't forget non-realistic graphics. The problems of rendering are unlikely to become inherently easier—I don't think raytracing will ever be "end all of graphics". And while "every singly animated movie" might be raytraced to some extent, it's highly unlikely any of them use pure raytracing to achieve the effect.

gfodor 13y ago
Uh, what. Sampled raytracing is the most natural approach to indirect lighting, displacement mapping, subsurface scattering, and anti-aliasing. As far as non-realistic rendering goes I am not sure how this is relevant, you can alter the properties of light and still use ray tracing, and many effects use image based techniques anyway. Raster will die in the long run, it's pretty obvious.
- lcrs 13y ago
  Raytracing may be conceptually the most natural but it's not always the best choice for a lot of these cases - displacement, motion blur, depth of field and anti-aliasing are still often handled much more quickly by micropolygon/scanline rendering even if the lighting and shading is raytraced. Hair and fur is pretty problematic with raytracing too. That said, physically-based shading is massively easier to art-direct, even if the "front end" as it were of the renderer isn't naively tracing rays from the camera. There's a killer set of slides and notes documenting ILM and Sony's switch to PBR here: http://renderwonk.com/publications/s2010-shading-course/ http://renderwonk.com/publications/s2010-shading-course/
- exDM69 13y ago
  > Raster will die in the long run, it's pretty obvious. Care to elaborate why you think this is the case? Even when doing raytracing, the fastest way to do the first pass is to rasterize your triangles and output hit data to textures (similarly to deferred rendering). Additionally, triangle rasterizerization can be used for vector graphics, etc while raytracing is inherently only for 3d content. I think that in the future we will have some kind of hardware acceleration for raytracing along with traditional triangle rasterization and they will be used together.
  - gfodor 13y ago
    In the long run graphics will probably converge on an approach that properly estimates the rendering equation. That's why I think ray tracing ultimately will be the preferred solution. (I'm talking on a extremely long timeline)
- dragonwriter 13y ago
  > Sampled raytracing is the most natural approach to indirect lighting Its been a while (~15 years or so) since I looked very deeply into this, but at that time I thought that radiosity was notably superior to raytracing for indirect lighting, and everyone and their cousin seemed to be doing hybrid ray tracing/radiosity systems for realistic rendering.
  - rayDawg 13y ago
    ah, what do we use to determine form factors in radiosity? oh yeah ray tracing.
- duaneb 13y ago
  > Sampled raytracing This covers about 100 different algorithms. Pick one.
  - rayDawg 13y ago
    I think that's the point.
    - duaneb 13y ago
      So, you didn't address the problem of "There's no obvious raytracing algorithm." All of the above algorithms have tradeoffs that make them ill advised in some sense. None of the above algorithms can handle displacement mapping or dynamic scenery with any speed. Get back to me when you solve those ridiculously combinatorial problem—any object can interact with any other object. And when you can animate objects in constant time between frames (as opposed to, at best, O(log(n)), and at worst, O(n)), maybe it'll be useful for realtime.
- rayDawg 13y ago
  >Raster will die in the long run, it's pretty obvious. I see, so I guess you plan to ray trace your gui and the text on screen too?
  - gfodor 13y ago
    What do you think?
subb 13y ago
Path tracing can be seen as a extension of ray tracing that supports a much broader range of effect like indirect lighting, soft shadows, anti-aliasing, etc. With the correct function for the material, you can simulate subsurface scattering relatively easily too. But, to me, the beauty of this technique goes beyond the effects you can achieve: it's an incredibly compact, uniform way of simulating light. Compared to rasterization, which to get the same result, you need a enormous code base that deals with very effect with caution. Adding a reflection in a rasterized scene might not reflect your shadows, etc. You need care about every possible interaction between every effect.

by duaneb 13y ago

gfodor 13y ago

Uh, what. Sampled raytracing is the most natural approach to indirect lighting, displacement mapping, subsurface scattering, and anti-aliasing. As far as non-realistic rendering goes I am not sure how this is relevant, you can alter the properties of light and still use ray tracing, and many effects use image based techniques anyway. Raster will die in the long run, it's pretty obvious.

lcrs 13y ago
Raytracing may be conceptually the most natural but it's not always the best choice for a lot of these cases - displacement, motion blur, depth of field and anti-aliasing are still often handled much more quickly by micropolygon/scanline rendering even if the lighting and shading is raytraced. Hair and fur is pretty problematic with raytracing too. That said, physically-based shading is massively easier to art-direct, even if the "front end" as it were of the renderer isn't naively tracing rays from the camera. There's a killer set of slides and notes documenting ILM and Sony's switch to PBR here: http://renderwonk.com/publications/s2010-shading-course/ http://renderwonk.com/publications/s2010-shading-course/
exDM69 13y ago
> Raster will die in the long run, it's pretty obvious. Care to elaborate why you think this is the case? Even when doing raytracing, the fastest way to do the first pass is to rasterize your triangles and output hit data to textures (similarly to deferred rendering). Additionally, triangle rasterizerization can be used for vector graphics, etc while raytracing is inherently only for 3d content. I think that in the future we will have some kind of hardware acceleration for raytracing along with traditional triangle rasterization and they will be used together.
- gfodor 13y ago
  In the long run graphics will probably converge on an approach that properly estimates the rendering equation. That's why I think ray tracing ultimately will be the preferred solution. (I'm talking on a extremely long timeline)
dragonwriter 13y ago
> Sampled raytracing is the most natural approach to indirect lighting Its been a while (~15 years or so) since I looked very deeply into this, but at that time I thought that radiosity was notably superior to raytracing for indirect lighting, and everyone and their cousin seemed to be doing hybrid ray tracing/radiosity systems for realistic rendering.
- rayDawg 13y ago
  ah, what do we use to determine form factors in radiosity? oh yeah ray tracing.
duaneb 13y ago
> Sampled raytracing This covers about 100 different algorithms. Pick one.
- rayDawg 13y ago
  I think that's the point.
  - duaneb 13y ago
    So, you didn't address the problem of "There's no obvious raytracing algorithm." All of the above algorithms have tradeoffs that make them ill advised in some sense. None of the above algorithms can handle displacement mapping or dynamic scenery with any speed. Get back to me when you solve those ridiculously combinatorial problem—any object can interact with any other object. And when you can animate objects in constant time between frames (as opposed to, at best, O(log(n)), and at worst, O(n)), maybe it'll be useful for realtime.
rayDawg 13y ago
>Raster will die in the long run, it's pretty obvious. I see, so I guess you plan to ray trace your gui and the text on screen too?
- gfodor 13y ago
  What do you think?

subb 13y ago

Path tracing can be seen as a extension of ray tracing that supports a much broader range of effect like indirect lighting, soft shadows, anti-aliasing, etc. With the correct function for the material, you can simulate subsurface scattering relatively easily too. But, to me, the beauty of this technique goes beyond the effects you can achieve: it's an incredibly compact, uniform way of simulating light. Compared to rasterization, which to get the same result, you need a enormous code base that deals with very effect with caution. Adding a reflection in a rasterized scene might not reflect your shadows, etc. You need care about every possible interaction between every effect.