3D Graphics - Ray Tracer

Scene Description Format

Each scene file can have the following keywords:

#COMMENTS

#global parameters
GLOBAL_AMBIENT_COLOR r g b
BACKGROUND_COLOR r g b
DEFAULT_REFRACTIVE_INDEX <double>
MAX_RECURSION_DEPTH <int>
FOV <double>

#scene objects
POSITIONAL_LIGHT r g b x y z
SPHERE x y z radius
TRIANGLE x1 y1 z1 x2 y2 z2 x3 y3 z3

#material properties
DIFFUSE_COLOR r g b
AMBIENT_COLOR r g b
SPECULAR_COLOR r g b
REFLECTANCE r g b
TRANSMITTANCE r g b
REFRACTIVE_INDEX <double>
SHININESS <double>

Sample scenes

• triangle scene file
• sphere scene file
• scene1-scene file This was generated using: raytrace scene1.txt 1024 768 -ppm scene1.ppm
  I then manually converted the PPM file to a PNG file. This took about 2 minutes to render on my 1.3ghz laptop. Notice that the green center sphere appears to be glowing. This is because it has a high reflectance value, while also having a moderatee transmittance value.[UPDATE 11/9/2004,9:32pm: I had a a bug in my refraction code, and scene1.png image was being incorrectly rendered. This has been fixed.]
• simple_scene-scene file This is rendered at 400 400. You shoudl be able to render this in under a minute on VCC south computers.[In release mode].
• simple_triangle_sphere-scene file

Notes:

• Material properties are maintained as state variables. So when you add an object(sphere or a triangle), it will be drawn with whatever the current material properties are(This is similar to what is done in OpenGL).
• Each token is seperated by one or more white spaces.
• r/g/b values are floating point numbers between 0.0 - 1.0
• SHININESS is the exponent value used in phong shading
• DEFAULT_REFRACTIVE_INDEX is used as the refractive index of the empty space in the scene(air).

PPM file format

PPM files are very easy to write. They are plain text ASCII files. You should be able to open them in Photoshop, GIMP, or use the unix convert command(convert a.ppm a.png) to convert it to another format.

A typical file looks like:

P3 <width> <height> <max color value>
r g b r g b r g b r g b ... (max 70 columns per line)

All values are integers in ASCII format. Each value is seperated by one or more white spaces(<newlines> or <space> or <tabs>). <max color value> should be 255 if you want a 24 bits/pixel RGB image. Here is an example 2x2 24bit color PPM file

P3 2 2 256
0 0 0 255 255 255 255 255 255 0 0 0

This should make a image which looks something like:

.#
#.

Here is some sample C++ code which write to a PPM file. The buffer it takes is the same as what you would give to glDrawPixels().

- Yogi