yart

description

• Yet another ray tracer.
• A simple ray tracer based on Blinn-Phong reflection model.

code

• Code is written in C++.
• include/ & src/ contains all the src code.
• examples/ contains some example scene files.
• textures/ contains texture files.
• assignments/ contains problem statements from which this raytracer was created.

documentation

• The documentation for the code is itself.

usage

how to run? [linux]

• Compile the raytracer using make to create an executable raytracer.
• The executable reads a scene file (and possibly some texture files) and generates a ppm image.
• Create the image of a scene using ./raytracer <path-to-scene-file>. It will be in the same directory as the scene file.
  • For example, ./raytracer examples/scene.txt creates examples/scene.ppm.

format of scene file

• The format is similar to .obj file format.
• Each line a the scene file defines something. Each line starts with a keyword and varying number of space separated parameters can follow.
• All colors are in normalized scale (0 - 1).
• The recognized keywords are as follows.
  • # ...: Comment. Will be ignored.
  • eye x y z: Camera position.
  • viewdir x y z: Camera viewing direction. Must be a unit vector.
  • updir x y z: Up direction. Must be a unit vector.
  • vfov angle: Vertical field of view in degrees.
  • imsize width height: Output image dimensions in pixels.
  • bkgcolor r g b: Background color.
  • light x y z w r g b: A light source.
    • x y z is position.
    • w can be 0 (directional source) or 1 (point source).
    • r g b is color.
  • mtlcolor Odr Odg Odb Osr Osg Osb ka kd ks n a h: Material color.
    • Odr Odg Odb is diffusion color.
    • Osr Osg Osb is specular color.
    • ka kd ks are ambient, diffusion and specular co-efficients respectively in the Blinn-Phong model.
    • n is the power in Blinn-Phong model.
    • a is opacity level (0 - 1).
    • h is refractive index.
  • texture <path-to-texture-file>: Path is assumed to start from raytracer executable directory. Has to be a valid ppm file.
  • sphere x y z radius: A spherical object.
  • v x y z: Vertex position.
  • vt u v: A texture coordinate. u & v must be in [0, 1].
  • vn x y z: A vertex normal definition. Must be a unit vector.
  • f ...: A face of a triangle.
    • All following arguments are indices of previously defined entities. The entities are counted from starting from 1 (and not 0).
    • f v1 v2 v3: v1 v2 v3: Vertex indices.
    • f v1/vt1 v2/vt2 v3/vt2: Vertex indices annotated with texture coordinate indices.
    • f v1//vn1 v2//vn2 v3//vn3: Vertex indices annotated with vertex normal indices.
    • f v1/vt1/vn1 v2/vt2/vn2 v3/vt3/vn3: Vertex indices annotated with texture coordinate indices & vertex normal indices.
  • parallel: Presence indicates that parallel projection is to be used. Default is perspective.
  • viewdist distance: Viewing distance for depth of field effect.
• Once a material color or texture is defined, it will be used for all the following objects in the scene until another is defined.
• For integer parameters, don't add a succeding decimal part.
  • 1 is ok.
  • 1. is not okay. 1.0 is not okay.
  • This is caused merely because of the cin construct behaviour and has nothing to do with the ray tracer.

ray tracer configuration

• Ray tracer has some configurable parameters, as listed with the defaults below.

name	description	default
CAMERA_MEDIUM_REFRACTIVE_INDEX	Refractive index of medium camera is placed in.	1
CAMERA_MEDIUM_OPACITY	Opacity of medium camera is placed in.	0
RECURSIVE_DEPTH	Number of times a ray reflects/refracts. Higher value produces more realistic effects.	6
SOFT_SHADOW_JITTER	Measure of dispersion of shadow rays. Higher value produces softer shadows.	0
NUM_SHADOW_RAYS_PER_POI	Number of shadow rays. Higher value produces softer shadows.	1
NUM_DISTRIBUTED_RAYS	Number of rays traced per pixel. Higher value produces more diffused image.	10
DISTRIBUTED_RAYS_JITTER	Measure of dispersion of rays traced per pixel. Higher value produces more diffused image.	5e-2

• To change config, directly edit these values in src/main.cpp and recompile.

roadmap

raytracer

• Ray sphere intersection.
• Ray triangle intersection (barycentric coordinates).
• Blinn-Phong reflection model.
• Point and directional source of light.
• Shadows.
• Smooth shadows.
• Subtractive shadows.
• Spheres.
• Triangules.
• Vertex normals, and their interpolation.
• Textures for spheres and triangles, Texture coordinates and their interpolation.
• Recursive ray tracing (using schlick’s approximation of the Fresnel reflectance).
• Refraction.
• Total internal reflection.
• Depth of field effect using distributed ray tracing.
• Parallel projection (not done properly, pulls the camera extremely far back).
• Spotlights.
• Attenuation.

I/O

• Parser. Recognized keywords, Input validation, Good error messages.
• PPM writer.
• PPM reader for textures.

misc

• To string for all types.
• Vec3d structure.

bug fixes

• Invalid number of args fix.
• Output file name fix.
• Accept empty lines.
• Ignore unknown keywords.
• Sometimes your rays go through triangles without detecting the intersection.
• Your texture parser doesnt always work, there might be newlines or whitespace at the end of a line.
• Your shadows aren't correct sometimes.
• texture paths.
• 1c testcases.
• 1d testcases.