5 ms·

Simple software rasterizer in a single C++11 header file

madsravn 12y ago
What exactly is the difference between this and for example a simple ray tracer? Seems like it takes a lot of the same steps.
- joeld42 12y ago
  This loops over the triangles and converts them to screen pixels. A ray tracer loops over screen pixels and checks if there are any triangles that overlap it.
  - Keyframe 12y ago
    More or less this. To expand a bit - rasterization converts lines or polygons to pixels via hidden line removal techniques (http://en.wikipedia.org/wiki/Hidden_line_removal http://en.wikipedia.org/wiki/Hidden_line_removal) and/or hidden surface techniques (http://en.wikipedia.org/wiki/Hidden_surface_determination http://en.wikipedia.org/wiki/Hidden_surface_determination) while ray tracing can mean a lot of different things, where most common and basic form is Whitted's ray tracing where final image is a grid of pixels with from each one there is a 'ray' shot towards the scene and checking if there is a collision with the object (polygon) and then turned towards each light source. In normal world, model is that light travels from light source, bounces from objects and comes to the camera - Whitted's algorithm is opposite where rays are shot from camera towards objects (modified by surface properties there) and towards light sources (less computation that way). Modern ray tracers involve Kajiya's equations and other fancy stuff.
    - alok-g 12y ago
      Thanks for the explanation. How are multiple hops in light path handled without having the computational complexity go insane?
      - beagle3 12y ago
        They aren't..... Some popular shortcuts include: - Cut at n hops (with n=4 or n=8 popular choices), defaulting to "ambient" light after that - Give each material an "ambient" color, so that you don't actually need to trace every pixel back into every light source (just into e.g. spotlights) - Solve a radiosity equation for the surface colors, and trace rays for textures/reflections. Complete ray tracing is, indeed, insane - in fact, to get high quality pictures and avoid aliasing, most ray tracers send multiple rays through every picture and average the result.
        beagle3 12y ago
        (too late to edit:) that was supposed to be "multiple rays through every pixel "
ricket 12y ago
I'm not a C++11 developer, I've done a little C++ in the past. What is the pride in putting all the code in the header file? Shouldn't the declarations be there, and the definitions be pulled out into a .cpp file? Is it somehow smaller, faster, more convenient to have it all in a header file?
- jgh 12y ago
  Header libraries are easier to add to your project because there are no build scripts to figure out or cross-compiling to do or whatever. A lot of Boost is header-only, for example. GLM (OpenGL Mathematics), too, is header-only. OTOH if you end up modifying a header that's included in a whole bunch of places, woe unto you.
  - TheDong 12y ago
    The reason Boost is headers only is you have to be a header to be generic. Implementations outside of headers have to friend / otherwise be not truly generic.
    - jgh 12y ago
      Yes, good point. You're right about that.
    - deleted 12y ago
      [deleted]
    - theyoungestgun 12y ago
      Assuming you mean friend in the standard cpp way, that's not exactly correct. http://stackoverflow.com/questions/495021/why-can-templates-only-be-implemented-in-the-header-file http://stackoverflow.com/questions/495021/why-can-templates-...
- deleted 12y ago
  [deleted]
- pjc50 12y ago
  It's unavoidable if you use templates in the interface. It tends to make builds disastrously slow though.
ykl 12y ago
I TA'd a rendering course once and wound up assigning a homework where the students implemented their own software rasterizers in CUDA. Before that homework, a lot of students didn't really understand what a rasterizer did. Afterwards, everyone got it.
- lfowles 12y ago
  Do you have links to any resources the students found handy? I'm not very familiar with anything to do with the graphics stack other than familiarity with some of the words.
  - nitrogen 12y ago
    I'm not the author of the original comment, but when I was in high school I found the Graphics Programming Black Book to be useful for understanding graphics primitives and how they can be implemented in software. It's available for free online: http://www.gamedev.net/page/resources/_/technical/graphics-programming-and-theory/graphics-programming-black-book-r1698 http://www.gamedev.net/page/resources/_/technical/graphics-p... Maybe start with chapter 38: http://downloads.gamedev.net/pdf/gpbb/gpbb38.pdf http://downloads.gamedev.net/pdf/gpbb/gpbb38.pdf
    - lfowles 12y ago
      Thanks, this is a great read (even though parts seem dated, for example, the TOC has chapters on the 386 and 486), I'm surprised that I haven't stumbled upon it before.
      - nitrogen 12y ago
        The latest Core i7 still has all the same instructions as a 386 or 486, so while these days you'd probably use SIMD instructions, the code will still run and run very, very fast.
rian 12y ago
Why aren't you using nullptr instead of casting NULL to your pointer type?
AshleysBrain 12y ago
Very cool - any perf stats though? Would be interesting to see how this compares to other software renderers.
pjc50 12y ago
I recently unearthed the code I wrote at school in 1996 which implemented a 3D Gouraud-shaded renderer that managed ~1000 triangles/sec on a 33MHz 486. It's a great learning experience doing this from scratch. Mine did Bresenham's algorithm for pixel fill rather than the winding approach used here.

What exactly is the difference between this and for example a simple ray tracer? Seems like it takes a lot of the same steps.

joeld42 12y ago
This loops over the triangles and converts them to screen pixels. A ray tracer loops over screen pixels and checks if there are any triangles that overlap it.
- Keyframe 12y ago
  More or less this. To expand a bit - rasterization converts lines or polygons to pixels via hidden line removal techniques (http://en.wikipedia.org/wiki/Hidden_line_removal http://en.wikipedia.org/wiki/Hidden_line_removal) and/or hidden surface techniques (http://en.wikipedia.org/wiki/Hidden_surface_determination http://en.wikipedia.org/wiki/Hidden_surface_determination) while ray tracing can mean a lot of different things, where most common and basic form is Whitted's ray tracing where final image is a grid of pixels with from each one there is a 'ray' shot towards the scene and checking if there is a collision with the object (polygon) and then turned towards each light source. In normal world, model is that light travels from light source, bounces from objects and comes to the camera - Whitted's algorithm is opposite where rays are shot from camera towards objects (modified by surface properties there) and towards light sources (less computation that way). Modern ray tracers involve Kajiya's equations and other fancy stuff.
  - alok-g 12y ago
    Thanks for the explanation. How are multiple hops in light path handled without having the computational complexity go insane?
    - beagle3 12y ago
      They aren't..... Some popular shortcuts include: - Cut at n hops (with n=4 or n=8 popular choices), defaulting to "ambient" light after that - Give each material an "ambient" color, so that you don't actually need to trace every pixel back into every light source (just into e.g. spotlights) - Solve a radiosity equation for the surface colors, and trace rays for textures/reflections. Complete ray tracing is, indeed, insane - in fact, to get high quality pictures and avoid aliasing, most ray tracers send multiple rays through every picture and average the result.
      - beagle3 12y ago
        (too late to edit:) that was supposed to be "multiple rays through every pixel "

ricket 12y ago

I'm not a C++11 developer, I've done a little C++ in the past. What is the pride in putting all the code in the header file? Shouldn't the declarations be there, and the definitions be pulled out into a .cpp file? Is it somehow smaller, faster, more convenient to have it all in a header file?

jgh 12y ago
Header libraries are easier to add to your project because there are no build scripts to figure out or cross-compiling to do or whatever. A lot of Boost is header-only, for example. GLM (OpenGL Mathematics), too, is header-only. OTOH if you end up modifying a header that's included in a whole bunch of places, woe unto you.
- TheDong 12y ago
  The reason Boost is headers only is you have to be a header to be generic. Implementations outside of headers have to friend / otherwise be not truly generic.
  - jgh 12y ago
    Yes, good point. You're right about that.
  - deleted 12y ago
    [deleted]
  - theyoungestgun 12y ago
    Assuming you mean friend in the standard cpp way, that's not exactly correct. http://stackoverflow.com/questions/495021/why-can-templates-only-be-implemented-in-the-header-file http://stackoverflow.com/questions/495021/why-can-templates-...
deleted 12y ago
[deleted]
pjc50 12y ago
It's unavoidable if you use templates in the interface. It tends to make builds disastrously slow though.

ykl 12y ago

I TA'd a rendering course once and wound up assigning a homework where the students implemented their own software rasterizers in CUDA. Before that homework, a lot of students didn't really understand what a rasterizer did. Afterwards, everyone got it.

lfowles 12y ago
Do you have links to any resources the students found handy? I'm not very familiar with anything to do with the graphics stack other than familiarity with some of the words.
- nitrogen 12y ago
  I'm not the author of the original comment, but when I was in high school I found the Graphics Programming Black Book to be useful for understanding graphics primitives and how they can be implemented in software. It's available for free online: http://www.gamedev.net/page/resources/_/technical/graphics-programming-and-theory/graphics-programming-black-book-r1698 http://www.gamedev.net/page/resources/_/technical/graphics-p... Maybe start with chapter 38: http://downloads.gamedev.net/pdf/gpbb/gpbb38.pdf http://downloads.gamedev.net/pdf/gpbb/gpbb38.pdf
  - lfowles 12y ago
    Thanks, this is a great read (even though parts seem dated, for example, the TOC has chapters on the 386 and 486), I'm surprised that I haven't stumbled upon it before.
    - nitrogen 12y ago
      The latest Core i7 still has all the same instructions as a 386 or 486, so while these days you'd probably use SIMD instructions, the code will still run and run very, very fast.

rian 12y ago

Why aren't you using nullptr instead of casting NULL to your pointer type?

AshleysBrain 12y ago

Very cool - any perf stats though? Would be interesting to see how this compares to other software renderers.

pjc50 12y ago

I recently unearthed the code I wrote at school in 1996 which implemented a 3D Gouraud-shaded renderer that managed ~1000 triangles/sec on a 33MHz 486. It's a great learning experience doing this from scratch. Mine did Bresenham's algorithm for pixel fill rather than the winding approach used here.