Radium Yang's Pathtracer

******************** 6000 Iterations, Ray Depth: 8, Depth of Field: focal length 13 *******************

##FEATURE LIST

• Basic
  • Raycasting
  • Diffuse surfaces
  • Perfect specular reflective surfaces
  • Cube intersection testing
  • Sphere surface point sampling
  • Stream compaction optimization
• Extra
  • Supersampling Anti-Alisasing
  • Depth of field
  • Refraction

###Feature Overview For the Pathtracing Algorithm and basic features' implementations, I mainly followed the raytracing slides in CIS 560 and pathtracing slices in CIS 565.

Extra Features:

• Depth of field

  • I referred to the algorithm posted here: http://ray-tracer-concept.blogspot.com/2011/12/depth-of-field.html
  • Find a focal plane before the camera, the new ray direction should come from the image plane to the focal point.

• Reflection/ Refraction

  • I referred to the algorithm posted here: http://ray-tracer-concept.blogspot.com/2011/12/refraction.html
  • Interesting bug... when calculating the accumulated reflective/refractive factor, failed to limit the factor to be required number. Solution:in reflection, if randomnumber < hasReflective, do reflection; else do diffuse. in refraction, if randomnumber < refractive, do refraction; else do reflection.
  • Example: iterations: 2000, trace depth: 8, hasReflect = 0.3, hasRefract = 0.8
    • Before:
    • After: (iterations: 2000, trace depth: 8)

• Stream compaction

  • reference: http://wiki.thrust.googlecode.com/hg-history/312700376feeadec0b1a679a259d66ff8512d5b3/html/group__stream__compaction.html#ga517b17ceafe31a9fc70ac5127bd626de
  • To accelerate the performance, using thrust to do stream compaction to delete rays which have already been hit to the background or light from the raypool. Thus, after each iteration, the valid rays in the ray pool will be decreased, which will help improve the performance.

• Supersampling Anti-Alisasing

• When casting the ray, jittered the pixel position on the image plane. (use thrust random number engine)

Performance Analysis

Progress Screenshots

• Step 1: ray intersection + diffuse color + soft shadow (sample 20) test

///// trace depth: 8 /////

• Step 2: use ray pool algorithm, diffuse + reflection + specular test

///// trace depth: 8 /////

• Step 3: add refraction & depth of field

///// trace depth: 8 /////

• Step 4: set customized scene (reflected walls) + performance tests

////// Iterations: 4000, trace depth: 2 /////

////// Iterations: 4000, trace depth: 5 /////

////// Iterations: 500, trace depth: 8 /////

////// Iterations: 6000, trace depth: 8 /////

===================

RUNNING THE CODE

The main function requires a scene description file (that is provided in data/scenes). The main function reads in the scene file by an argument as such : 'scene=[sceneFileName]'

If you are using Visual Studio, you can set this in the Debugging > Command Arguments section in the Project properties.

SCENE FORMAT

This project uses a custom scene description format. Scene files are flat text files that describe all geometry, materials, lights, cameras, render settings, and animation frames inside of the scene. Items in the format are delimited by new lines, and comments can be added at the end of each line preceded with a double-slash.

Materials are defined in the following fashion:

• MATERIAL (material ID) //material header
• RGB (float r) (float g) (float b) //diffuse color
• SPECX (float specx) //specular exponent
• SPECRGB (float r) (float g) (float b) //specular color
• REFL (bool refl) //reflectivity flag, 0 for no, 1 for yes
• REFR (bool refr) //refractivity flag, 0 for no, 1 for yes
• REFRIOR (float ior) //index of refraction for Fresnel effects
• SCATTER (float scatter) //scatter flag, 0 for no, 1 for yes
• ABSCOEFF (float r) (float b) (float g) //absorption coefficient for scattering
• RSCTCOEFF (float rsctcoeff) //reduced scattering coefficient
• EMITTANCE (float emittance) //the emittance of the material. Anything >0 makes the material a light source.

Cameras are defined in the following fashion:

• CAMERA //camera header
• RES (float x) (float y) //resolution
• FOVY (float fovy) //vertical field of view half-angle. the horizonal angle is calculated from this and the reslution
• ITERATIONS (float interations) //how many iterations to refine the image, only relevant for supersampled antialiasing, depth of field, area lights, and other distributed raytracing applications
• FILE (string filename) //file to output render to upon completion
• frame (frame number) //start of a frame
• EYE (float x) (float y) (float z) //camera's position in worldspace
• VIEW (float x) (float y) (float z) //camera's view direction
• UP (float x) (float y) (float z) //camera's up vector

Objects are defined in the following fashion:

• OBJECT (object ID) //object header
• (cube OR sphere OR mesh) //type of object, can be either "cube", "sphere", or "mesh". Note that cubes and spheres are unit sized and centered at the origin.
• material (material ID) //material to assign this object
• frame (frame number) //start of a frame
• TRANS (float transx) (float transy) (float transz) //translation
• ROTAT (float rotationx) (float rotationy) (float rotationz) //rotation
• SCALE (float scalex) (float scaley) (float scalez) //scale

An example scene file setting up two frames inside of a Cornell Box can be found in the scenes/ directory.

An example of a mesh object is as follows:

OBJECT 0 mesh tetra.obj material 0 frame 0 TRANS 0 5 -5 ROTAT 0 90 0 SCALE .01 10 10