Renderer

Introduction
============

This package allows interactive 3D visualization of triangle meshes.

It contains the source code for a straightforward implementation of 
basic principles in polygon-related graphics theory.  You can use these 
sources to familiarize yourself with:

 - 3D transformations
 - Phong shading
 - Z-buffering
 - Shadow mapping (with soft shadows)
 - Portable display and keyboard handling through SDL. 
 
The sources include support for OpenMP and Intel Threading Building 
Blocks, so they take advantage of multi-core CPUs and execute faster.

The supported 3D formats are:

- .3ds, the well known 3D Studio format (via lib3ds), and...
- .tri, a simple binary dump of vertex and triangle data.
- .ply (partial support, for 3D objects saved from shadevis)

The code is orchestrated with autoconf/automake, so it compiles and 
runs cleanly on many platforms (tested on Linux/x86, Linux/amd64-em64t, 
Windows/x86 (MinGW), FreeBSD/amd64, Mac OS/X and OpenBSD/amd64).

The sources are available under the GNU license (read COPYING for details).

This is more or less a reference implementation. I wanted to write my
polygon rendering code in as clear a manner as possible, and to also
add support for shadow mapping and real phong shading. The code uses
floating point almost everywhere, and calculates the complete lighting 
equation per pixel. When I first wrote this (late 2003), it was far from
real-time... Then again, as of 2007, a Core2Duo can render the train
object (see 3D-Objects folder) at around 32fps (under Debian64 with Intel 
Threading Building Blocks). And since OpenMP/TBB will automatically use 
as many cores as are available, the multi-core future seems... 
interesting :-)

COMPILE
=======

If you don't have SDL installed, download it and install it first
(http://www.sdl.org). It is required for portable display and 
keyboard handling. I used SDL version 1.2.5 but older versions
of the library should also work just as well. If you use any of
the Linux distros and install SDL from packages, make sure you
also install the SDL development packages (that is, the SDL header files 
and libraries).

The package includes the sources for lib3ds-1.3.0, so you don't
need to do anything about lib3ds.

Optionally, if you have a multicore/multi-CPU machine and you want 
to take advantage of your extra cores, you must either have GCC >= 4.3.2
(which correctly supports OpenMP) or Intel Threading Building Blocks 
(http://www.threadingbuildingblocks.org) installed. 

Executive summary:

 ./configure
 make

You can also influence the compilation by passing your own compiler
flags to 'configure'. For my Core2Duo, instead of plain './configure', 
I use:

CXXFLAGS="-O3 -mfpmath=sse -march=core2 -msse -msse2 -msse3 -mrecip" ./configure

...which bumps the rendering speed up by 24%. You can also compile 
with Intel's compiler, if you wish (on my Core2Duo machine it futher
speeds up rendering by another 10%). Just edit and use the two build
scripts in the contrib/ directory (i.e. fix the TBB and ICPC paths 
and run them).

RUNNING
=======

After a successful make, you can fly around with...

 cd 3D-Objects
 ../src/renderer/renderer statue.ply

Hit 'R' to stop/start auto-spin.
Fly using the cursor keys,A,Z - and rotate the light with W. 
SPACE changes the rendering mode, and ESC quits. 
S and F are 'strafe' left/right, while E and D are 'strafe' up/down
(strafe keys don't work in auto-spin mode).

Have a look at the other meshes as well (in folder 3D-Objects). 

Also, if you want sharp shadows (20% faster rendering), comment out
the line that defines SOFTSHADOWS in src/common/Screen.cc.

TALES OF MULTICORE
==================

This code was single threaded until late 2007. At that point, I heard
about OpenMP, and decided to try it out. I was amazed at how easy 
it was to make the code "OpenMP-aware": I simply added a couple of pragmas 
before the for-loops that drew the triangles and the shadow buffers, 
and ...presto!

The only things I had to change were static variables, which had to be 
moved to stack space. Threading code can't tolerate global/static data, 
because race conditions immediately appeared when more than one thread 
worked on them.

Only two compilers truly supported OpenMP at the time: Intel's compiler 
(version 8.1) and Microsoft's CL. GCC unfortunately died with 'internal 
compiler error'. I reported this to the GCC forums, found out that 
I was not the only one who had noticed, and was told (by the forum guys) 
to wait.

While waiting for GCC to catch up, I kept researching multicore technologies.
Functional languages seem particularly adept to SMP, and I've put them
next in line in my R&D agenda (Ocaml and F# in particular). Before leaving
C++ behind, though, I heard about Intel Threading Building Blocks (TBB)
and decided to put them to the test. TBB is a portable set of C++ templates 
that makes writing threading code a lot easier than legacy APIs 
(CreateThread, _beginthread, pthread_create, etc). TBB is also open-source,
so it was easy to work with and figure out its internals. Truth be told,
TBB required a bit more changes in my code (OpenMP required almost no changes).
Still, it is a vast improvement compared to conventional threading APIs.

I must confess I have not invested a lot of effort in using these technologies;
I only enhanced my two main rendering loops to make them SMP aware. Still, 
this was enough to boost the speed (on my Core2Duo) by 80%! Judging by the 
effort invested, this is one of the best bargains I've ever met in my 
programming career.

As of now (October 2008), GCC 4.3.2 is now up to speed and compiles OpenMP 
code just fine. TBB is of course running perfectly (since it is simply a C++
template library), so choose freely between any of the two, and easily 
achieve portable multithreading. 

When I say portable, I mean it: "./configure && make" is enough
to create:

1. OpenMP binaries for...

- Windows (via TDM/MinGW GCC 4.3.2)
- Debian Linux Etch (both 32 and 64bit, via manually-built GCC 4.3.2)
- Debian Linux Etch 32bit (via Intel's 10.1.017 compiler)

2. TBB binaries ("./configure --disable-openmp --enable-tbb") for...

- Debian Linux Etch (both 32 and 64bit, via manually-built GCC 4.3.2)
- Debian Linux Etch 32bit (via Intel's 10.1.017 compiler)
- FreeBSD/64

3. Single-threaded binaries for...

- Poor OpenBSD/64: it doesn't have real, SMP threads. Not yet, at least :-)
  It only has user-space ones (as Linux did at some point).  
  But it does compile the code, albeit in single-threaded mode.
- Mac OS/X: Tested by a friend with a single core OS/X machine:
  Compiles and runs just fine (albeit in single-threaded mode).
  I don't know if OS/X GCC has adequate support for OpenMP; if it doesn't,
  GCC 4.3.2 will surely be available for it soon.

Talk about portable code!

If you're still in the dark ages and use legacy APIs (like CreateThread, 
_beginthread, pthread_create, etc) you are really missing out. 

Enjoy!

Thanassis Tsiodras, Dr.-Ing.
ttsiodras_at-no-spam_thanks-gmail_dot-com