Nori is a minimalistic ray tracer written in C++. It runs on Windows, Linux, and Mac OS and provides a foundation for the homework assignments in the course Advanced Computer Graphics taught at EPFL.

While Nori provides much support code to simplify your development work as much as possible, the code that you will initially receive from us does very little: it loads a scene and saves a rendered image as an OpenEXR image—but the actual rendering code is missing, hence the output image just consists of black pixels. Your task will be to extend this system to a full-fledged physically-based renderer as part of programming assignments and your final project.

## Core features

The Nori base code provides many features that would be tedious to implement from scratch. The following are included:
• A simple GUI to watch images as they render
• An XML-based scene file loader
• Basic point/vector/normal/ray/bounding box classes
• A pseudorandom number generator (PCG32)
• Support for saving output as OpenEXR files
• A loader for Wavefront OBJ files
• Ray-triangle intersection
• Image reconstruction filters
• Statistical $$\chi^2$$- and $$t$$-tests to verify sampling code
• A graphical visualization tool that can be used to inspect and validate sampling code.
• An efficient parallel bounding volume hierarchy builder (provided in the third assignment)

### References

You may find the following general references useful:

#### Permissible sources of information

Feel free to consult additional references when completing projects, but remember cite them in your writeup.

When asked to implement feature $$X$$, we request that you don't go and read the source code of the implementation of $$X$$ in some other renderer, because you will likely not learn much in the process. The PBRT book is excluded from this rule. If in doubt, get in touch with the course staff.

## Guidelines for homework submissions

The goal of these exercises is to help you create the foundation of a good renderer for subsequent assignments and the rendering competition. It is your job to convince us that you have implemented the assignments correctly, through the information provided in your reports and the quality/readability of your code. We will deduct points for poorly written code or inconclusive comparisons/validations in your report. Make sure to start working on the homework as early as possible. Building your own advanced renderer is a lot of fun. Use this great opportunity, and don’t forget to have fun!

### What to submit?

The codebase with your solution and source files. Do NOT include: binaries (i.e. remove the build folder), external dependencies (i.e. remove nori/ext) and class-provided scenes (i.e. remove nori/scenes).

Include a completed report based on the template available here and adhere to the following conventions:

• Structure your report using numbers and titles following those of the assignment.
• For every task include all images you generated in a format that is viewable within a web browser. You can use HDRI Tools or Photoshop to tonemap you images and save them as JPEG or PNG images. We recommend tonemapping your images by just changing exposure and using sRGB (if available) or a with a gamma value of 2.2.
• Include descriptions of encountered problems, a list of external libraries that you used (if applicable) and the time you spent on each task.
The task descriptions may contain more specific instructions on what has to be included. Solutions to programming and theoretical assignments should be uploaded on Moodle.

We would appreciate any comments or criticism to improve the projects in future years. Please use the first section of your report to provide feedback--naturally, this part will not be graded. Examples of information that is useful to us includes:

• How much time did you spend on the assignment? How was it divided between designing, coding, and testing?
• What advice should we have given you before you started?
• What was hard or surprising about the assignment?
• What did you like or dislike? What else would you change?

### Late submissions

Late submissions are subject to the grading scheme as discussed in the first lecture: submitting a homework late (which is interpreted strictly, i.e. using the exact submission time on Moodle) consumes a late day. You have a budget of 3 "free" late days that can be used for any assignment without penalties. After this budget is used up, the grade of the late submission is affected as follows:

• 1 day late: max 75% of score
• 2 days late: max 50% of score
• 3 days late or more: 0%