Studying with The Graphics Codex

This is a post where I talk about the projects of The Graphics Codex by Morgan Mcguire and present my results for each one. I was having a bit of a trouble focusing on one thing at a time because I wanted to do so many things! So, I decided to end my struggle by following a specific “curriculum” which has concrete goals to narrow down my selection. Every project requires to read up on specific subjects that are more beginner oriented but it is a nice refresher of the basics.

I talk about the strengths and weaknesses of each project, what I’ve learned and what I’ve achieved following the guidelines of each one. I hope to inspire anyone who happened to stumble upon this post and manages to finish it. All code will be uploaded on Github and I will introduce more chapters in this post as I complete each project.

1. Cubes

The “Cubes” project is the first one in the series and serves as an introduction to many things such as coordinates systems and positioning in 3D space and the G3D Innovation Engine. This is a very good starting point to learn Computer Graphics because the basic rendering is already implemented, there is a streamlined way to add GUI elements and provides the way of structuring the code when working with a real-time engine.

The pros of this project are:

  1. It is a great introduction which doesn’t require any previous knowledge; only C++ familiarity.
  2. Already implemented controls (FPS camera), debug GUI and camera effects adjustments.
  3. It touches on procedural generation without being too complicated (with the generation of a staircase).

The cons of the project are:

  1. The bloom effect is bugged and it doesn’t work well with spot lights. Since it is enabled by default, the reader needs to fiddle with the debug GUI and disable/enable everything until they find the culprit.
  2. The documentation on how to write in the .Any “language” doesn’t refer to every object and can be a huge pain for beginners. The only hope is to scour through the samples in hopes of finding something that fits our needs.

The final “assignment” of this project was to create a complex scene using only cubes. My “deliverable” read an image and created a cube grid where each cube corresponds to one pixel and the cube’s height depended on the luminance of the corresponding pixel. Below are two renders of a scene rendered in G3D.

Overall, I think it is a great learning experience but the cons become more important the less someone is experienced with C++ and reading documentation of software. It should, at least, mention some sample files in the G3D repository to introduce this way of thinking and searching to the beginners.

2. Meshes

The next project speaks about topology and expands on procedural generation by requiring the creation of a wine glass. The reader should first create a cylinder, then create a heightfield and, lastly, create a wine glass using only it’s contour from a half cross-section. My “deliverable” for the Cubes project was like a heightfield but with many more objects and way more image sampling because it is a recreation of the image with cubes (it can get out of hand with high resolution images and G3D didn’t like that).

The pros of the project are:

  1. It speaks about topology and when someone finally understands that a mug is the same as a torus topologically because they have only one hole, a very big “AHA!” arises.
  2. Procedural generation.

The cons of the project are:

  1. The setup of the existing GUI is not “correct” and the reader needs to debug it in order to place more items in the same style. This is something that I would normally classify as a “pro” because it is a learning experience but the reader already has many things to keep track of; putting more obstacles does not help.

The requirement for the wine glass is that the glass should be created only from a contour and an optional GUI element would be the number of rotational slices to generate. Since I didn’t want to give the numbers by hand or interpolate a Bezier curve and import the points, I decided to (again) use an image as input. The specification for that image is that it has to be grayscale with black indicating point of mass and white indicating surrounding space. After generating the wine glass, I had to present it in a stylish way.

For the generation of the glass, I simply read the image lines to find start and end points of mass and then translate them to a normalized system to preserve the aspect ratio. The initial results were encouraging but I didn’t like that there was too much generated geometry (one ring for every pixel line). So, I added a “Quality” slider which translates to a distance and an angle criterion that evaluate if a ring should be inserted or not. The lower the “Quality” the less rings are inserted and the higher the “Quality” the more faithful is the result to the input. I ended up liking the lower quality results more because they were cleaner.

From left to right: i) the grayscale image input, ii) the raw result where every pixel line generates a cylindrical ring, iii) a low quality result with the naive angle criterion and iv) the low quality result with the distance and angle criteria.

I decided to produce a more sophisticated presentation for this project with a more refined glass along with some plates and place them in a bar setting. The plates are generated with the same method as the glass. Below are the render in G3D, the input images and the resulting meshes.

I felt a great sense of accomplishment when I saw my creations sitting there and pretending to be realistically rendered. It is a very nice feeling to have something of a “closure” and see every bit fit together to produce a final result. This chapter was very good.

3. Geometry Design

This will not be my next project, because I have decided to implement the “Instancing support for a ray tracer” which requires the Rays project. So, the 4th project is next.

4. Rays

The JIRA issue is made and in status “In development”.

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