# crt - the C raytracer #

Raytracing is just one technique used in generating realistic images using a
computer. In the real world, what we see is a direct result of light photons
being emitted from a source (such as the sun, a light bulb, etc), bouncing off
objects, and eventually being collected by our eyes. As simple as this is, it's
still a lot of work for a computer to do.

This is because many of the photons aren't actually percieved by us. Raytracing
greatly simplifies the way lighting works by viewing light in the opposition
direction. Instead of tracing photons from the sources, we trace a ray from our
eye through the scene. This means we only calculate the rays of light that
matter to us.

The raytracing algorithm itself is relatively simple. For each pixel in the
image, we trace a ray through that pixel and into the scene. We then check for
an intersection with any of the objects in the scene. If the ray hits nothing,
then that pixel becomes black. If the ray does intersect an object, that pixel
becomes that objects color.

After that, the pixel's color can be modified based on various other algorithms,
such as lighting algorithms, reflections, etc. Reflections can easily be
calculated by using the ray tracing algorithm recursively. Essentially, the
reflective object becomes the "eye", and the scene is re-traced from that view
point.

## scene files ##

crt uses a modular scene input scheme to allow scenes to be loaded from a
variety of sources. Currently crt uses an XML plugin to load scene definition
files from an XML file. An example of an object's XML:

    <sphere x="1.0" y="2.0" z="0.0" radius="1.0">
     <material r="1.0" g="0.0" b="0.0" diffuse="1.0" />
    </sphere>

## image output ##

Again, crt uses a modular image output scheme to write images. Currently crt
supports writing directly to a bitmap image.

## features ##

Currently crt features the following:

  * 3 different shapes: spheres, axis-aligned boxes, and planes
  * Point and Area light sources
  * Shadows
  * Anti-Aliasing
  * Reflections
  * Refractions

## generated images ##

<div class="image">
 <img alt="scene1" src="/code/crt/images/scene1.png" />
 <div class="image_footer">Scene 1 (<a href="/code/crt/images/scene1_1920x1200.png">1920x1200</a>)</div>
</div>

<div class="image">
 <img alt="scene2" src="/code/crt/images/scene2.png" />
 <div class="image_footer">Scene 2 (<a href="/code/crt/images/scene2_1920x1200.png">1920x1200</a>)</div>
</div>

<div class="image">
 <img alt="scene3" src="/code/crt/images/scene3.png" />
 <div class="image_footer">Scene 3 (<a href="/code/crt/images/scene3_1920x1200.png">1920x1200</a>)</div>
</div>

## GIT ##

You can checkout a bleeding-edge version of crt with git using the following
command:

    git clone http://voidsplat.org/code/crt/crt.git