Sebastian Kopacz

Computer Graphics Rendering Assignments

  • Mar 22, 2019

Various assignments I did for the Rendering course (Computer Science 591 at the University of Calgary) I took in winter 2019.

Source code is self-hosted on my home Git-Gogs server which is only accessible from my home network.

BVH vs KD

Features

  • Made the test scene in Blender then figured out how to export it to PBRT and automate as much of the process as possible.
  • I then just added models to a selected region in the scene and had a batch script rendering each scene with PBRT using both KD and BVH acceleration.
  • Once that was done all that was needed was to graph the results and realize that both increase at the same rate with just a slight difference in speed.

Cycles Render

PBRT Render

Examples of the test objects I added to the scene

Comparison Graph

Increase in render time as the number of test objects in the scene increases. Both time increases are clearly logarithmic as they barely increase while the 𝑥-axis is exponential. Which matches the literature time complexity (𝑂(log(𝑛)) for BVH and KD Trees. Rendered using an AMD Threadripper 1950x.

Credits

Polygonal Apertures

Features

  • By default PBRT only has circular apertures.
  • Extended PBRT to support any regular polygonal aperture.
  • Also supports stars of any polygonal number of points despite the bonus only requiring 5 pointed stars.

Default PBRT Aperture

Regular 5-Sided Aperture

5-Point Star Aperture

Regular triangle aperture

3-Point Star Aperture

Credits

Sampling Fix

PBRT has a bug where it will sample a half disk the same as a full disk, our task was to fix this by changing the samples so that it would be from just the half disk rather than the entire disk. Unfortunately I used rejection sampling instead of properly transforming the samples to be uniformly spaced on the disk. As such my implementation was incorrect and visually unimpressive.

Features

  • Uses rejection sampling to ignore invalid rays.

The issue

My horrible fix

(Note how the brightness decreases due to rejection sampling)

Credits

Deferred Rendering

Features

  • Based on my model viewer from Intro to Computer Graphics.
    • As such shares many of the features that were implemented for that assignment.
  • Main addition is the deferred rendering pipeline.
  • Also has Oren-Nayer diffuse shading in addition to Phong shading.

Phong lighting

Oren-Nayer shading

Sigma = 0

Sigma = 20

Credits

SSAO

Features

  • Continuation of the previous assignment (assignment 4, deferred rendering) so many of the previous features carried over.
  • Implemented Crytek’s SSAO
  • Rocket model was a slightly upgraded version of the rocket in the scene for assignment 1.

Without SSAO

With SSAO

Credits