miniRT

Thanks Linuswidmer for the collaboration on this project!

Raytracing is an old - yet still very common method - rendering algorithm to generate digital images. Raytracing is more expensive in computation the the “Rasterization” method,but it produces a much higher degree of visual realism.

The goal of this project was to implement a ray tracing algorithm in C (with a minimum of external functions)! The main goal of miniRT is the implementation of any mathematics or physic formulas, necessary for the tracing.

The following images are generated by this program:

Learning goals

• Understand representations and transformations of 3D scenes in computer graphics
• Calculation of intersection between vectors and 3D-objects (spheres, planes, cylinders, ...).
• How to translate the above points into pure C-code
• And of course how to collaborate on a project and split workload in an efficient way!

Core features of this raytracer are:

• Render spheres, planes, cylinders and cones with any orienation and position in space
• Have a variable viewpoint, view orientation as well as field of view
• Combining ambient and diffuse light sources with different colors and phong effect

Allowed external functions / libraries:

• open, close, read, write, printf, malloc, free, perror, strerror, exit
• All functions of the math library (-lm man man 3 math)
• All functions of the MinilibX - graphical library provided from 42 (see submodule)
• Libft - own library with basic functions such as calloc, strncpm, etc. (see submodule)

As usual: All heap allocated memory space must be properly freed. No leaks will be tolerated.

Usage

Note that the program is written with Linux. Other operating systems were not tested.

Installing and Compiling

1. Clone the repository and its submodule by git clone --recursive <project SSH/URL>
2. direct to the cloned folder cd <folder_name>
3. make (automatically compile the libft and MiniLibX)

Check the MiniLibX ReadMe in case of problems with the library.

NOTE: by default the program compiles with the extras of cones, multiple light sources, colored light and phong effect. To disable the extras, set DBONUS in the path variable (export DBONUS=0). Additional debug values will be printed in the prompt after setting export DPARSER=1 and export DRENDER=1 (don't forget to re-compile!!!)

Execution

The proram will read the input for the scene from a file in .rt format. The */scenes/valid/ folder contains some example scenes.

• Example: ./miniRT ./scenes/valid/eval_sheet_pillars.rt

Scene Format

Rules for scene format Every scene must contain at least a Viewpoint (C), an ambient lighting (A) and one or more diffuse light sources (L):

• Identifier (C) ; coordinates (x,y,z) ; orientation vector (x,y,z) [-1..1] ; field of view (deg) [1..179]
• Identifier (A) ; intensity ([0..1]) ; colors (r,g,b) [0..255]
• Identifier (L) ; coordinates (x,y,z) ; intensity ([0..1]) ; colors (r,g,b) [0..255]

Additionally the Scene can contain Objects such as sphere (sp), plane (pl), cylinder (cy) and cone (co)

• Identifier (sp) ; center (x,y,z) ; diameter ; color (r,g,b) [0..255]
• Identifier (pl) ; coordinates (x,y,z) ; orientation vector (x,y,z) orthogonal to plane [-1..1] ; color (r,g,b) [0..255]
• Identifier (cy) ; center (x,y,z) ; orientation vector (x,y,z) [-1..1] ; diameter ; height ; color (r,g,b) [0..255]
• Identifier (co) ; coordinates (x,y,z) of vertex) ; orientation vector (x,y,z) [-1..1] ; opening angle (deg) [1..179] ; color (r,g,b) [0..255]

Given the above rules we can define a Scene:

C   0,5,-15   0,0,1   80
A                     0.2    90,90,255
L   0,6,-10           1     255,255,255


pl  1,-1.5,10   0,1,0             255,255,255
sp  9,0.0,0.0           3.6       0,255,0
cy  -7,1.5,0    1,0,0   4     6   0,255,255
co  3,7,0       0,-1,0  23        255,0,0

which renders to:

Fancy pictures

The following pictures were rendered with the program:

Sources

Realizing this project requires a deeper understanding of the raytracing algorithm as well as some literacy in linear algebra. The following list is a recommendation of sources for anyone who wants to know more about the topic:

Topic	Link
Linear Algebra	3Blue1Browns Playlist on Linear Algebra
Raytracing technique	Scratchapixel, Computer Graphics From Scratch
Diffuse and Specular Light	Diffuse Light , Blinn-Phong Model
Cone	What is a cone???, Cone - Ray intersection
Sphere	Sphere - Ray intersection