Tracerr

A simple raytracing program

Overview

This program was done as the final project for the Udacity C++ Nanodegree.
The program supports rendering of spheres, triangles and rectangles as basic primitive shapes. It also includes the capability to render .obj 3D models.
The program is capable of simulating not only the basic Phong illumination model (ambient, diffusion and specular light) but also shadows, reflections and refractions
The scenes to render are stored in text protobufs that can be used to modify said scenes.
The code is inspired by tinytracer by Dimitry Sokolov (specially some of the math behind raytracing). The rest of the code was done to practice the stuff that was covered during the nanodegree.
I also chose to use Eigen for the linear algebra due to its easy to use, speed and built-in methods.

Install dependencies

The instructions here are aimed for Ubuntu (tested on 20.04), for other platforms please check the respective library sites

Dependencies:

1. Git
2. CMake 3.16
3. Eigen 3.3.7
4. Protobuf 3.6.1
5. Python>=3.6 if using python

To install them run the following command:

$ sudo apt -y install git build-essential cmake libprotobuf-dev protobuf-compiler libeigen3-dev

It also uses the STB library to encode the image files. The required files are already included in the repo (include directory)

NOTE: If you want (NOT REQUIRED) to force the generation of the C++ header and source files from scene.proto file, you can run the following command within the main project folder

$ protoc -I=./proto --cpp_out=./proto ./proto/scene.proto

How to build

Once you have all the dependencies installed you can compile the program with CMake and Make

Python

$ git clone https://github.com/DLopezMadrid/tracerr.git  
$ cd tracerr
$ pip install .

C++

NOTE: This code uses C++17 features

$ git clone https://github.com/DLopezMadrid/tracerr.git  
$ cd tracerr
$ mkdir build    
$ cd build    
$ cmake ..    
$ make    

How to run

To render a scene, the program is launched from the terminal and takes the -r option and the path to a prototext file describing the scene.

$ ./tracerr -r {PATH_TO_PROTOTEXT_FILE}

Example:

$ ./tracerr -r ./../scenes/simple.textproto

The scene parameters are explained in the next section.

In order to create a new the scene, you will need to make a new prototext file. You can ask the program to create an example scene, a commented empty template and a non-commented empty template with the following commands

  -t SAVEFILE_FOR_TEMPLATE_FILE -> Generates an empty Template with comments for a scene   
  -u SAVEFILE_FOR_UNCOMMENTED_TEMPLATE_FILE -> Generates an empty Template WITHOUT comments for a scene   
  -e SAVEFILE_FOR_EXAMPLE_SCENE -> Generates a textproto file of a Example scene and saves it to the specified file   

Example to create a commented template file:

$ ./tracerr -u my_new_scene.textproto

You can also find some predefined scenes in the ./scene folder

• simple.textproto: random scene that contains an element of every shape and an obj file
• simple_spheres.textproto: another example with just a few spheres and a custom background color
• sphere_field_with_duck.textproto: built on top of simple_spheres one but with 400 randomly generated smaller spheres and a duck 3D model
• suzanne.textproto: just a simple obj 3D model on a plain background

NOTE: In a i7 Skylake machine it takes around 25s to render the demo scene (./scenes/sphere_field_with_duck.textproto) shown in the cover image above (2000px x 1000px) (400 randomly generated spheres + 3D duck model)

For faster execution you can reduce the resolution (width & height parameters). You can also comment out any of the shapes in the scene config file
The resulting image will be saved in the build directory under the filename that you specify in the prototext file (fname parameter)

Python

The Python module follows the same functionality as C++ and provides the following functions:

tracerr.GenerateExample()
tracerr.GenerateTemplateNoComment()
tracerr.GenerateTemplate()
tracerr.RenderScene()

The Python module can be used as follows:

import tracerr
tracerr.RenderScene('PATH_TO_PROTOTEXT_FILE')

Scene definition

Scene configuration

The protobuf schema for the scene files is defined in the ./proto/scene.proto file
The following fields are mandatory

 int32 width;
 int32 height;
 bool saveFile [default = true];

• width: image width in pixels
• height: image height in pixels
• saveFile: bool to specify if you wish to save the image

There are also other scene configuration attributes that are optional

 string fname [default = "RenderTest.png"];
 bool show_elapsed_time [default = true];
 bool show_checkerboard [default = false];
 Color background_color;
 float ambient_light;

• fname: filename for the saved image
• show_elapsed_time: prints the time taken to render the scene to the console
• show_checkerboard: draws the checkerboard floor plane
• background_color: specifies a custom background color using the Color type (see below)
• ambient_light: specifies the ambient light level (values 0 - 1)

Supporting types

There is a number of types created to make the object definition more structured

 message Pos {
    required float x = 1;
    required float y = 2;
    required float z = 3;
  }
 message Color{
   required int32 r = 1;
   required int32 g = 2;
   required int32 b = 3;
 }
 message Material{
   message Color_diff{
     required int32 r = 1;
     required int32 g = 2;
     required int32 b = 3;
   }
   message Albedo{
     required float a0 = 1;
     required float a1 = 2;
     required float a2 = 3;
     required float a3 = 4;
   }
   required Color_diff color = 1;
   required Albedo albedo = 2;
   required float specular_comp = 3;
   required float refractive_index = 4;
 }
 enum MaterialType{
   ivory = 0;
   red_rubber = 1;
   green_rubber = 2;
   blue_rubber = 3;
   orange_rubber = 4;
   pink_rubber = 5;
   red_plastic = 6;
   black_plastic = 7;
   mirror = 8;
   glass = 9;
   chessboard = 10;
 }

• Pos: defines a cartesian (X, Y, Z) position in space
• Color: defines an RGB color (0 - 255)
• Material: describes a new material containing custom diffuse color, albedo, specular component and refractive index components
• MaterialType: if you wish to use one of the predefined materials

Light sources

To define a light source:

 message Light{
   required Pos position = 1;
   required float intensity = 2;
 }

Example:

light{
  position{
    x: 0
    y: 5
    z: 0
  }
  intensity: 1.5
}

Spheres, triangles and rectangles

To define primitive shapes

  message Sphere{
    required Pos position = 1;
    required float radius = 2;
    optional MaterialType material = 3;
    optional bool custom_material_enabled = 4 [default = false];
    optional Material custom_material = 5;
  }
  message Triangle{
    required Pos p0 = 1;
    required Pos p1 = 2;
    required Pos p2 = 3;
    optional MaterialType material = 4;
    optional bool custom_material_enabled = 5 [default = false];
    optional Material custom_material = 6;
  }
  message Rectangle{
    required Pos p0 = 1;
    required Pos p1 = 2;
    required Pos p2 = 3;
    required Pos p3 = 4;
    optional MaterialType material = 5;
    optional bool custom_material_enabled = 6 [default = false];
    optional Material custom_material = 7;
  }

Examples:

sphere{
  position{
    x: 3
    y: 0
    z: -4
  }
  radius: 0.5
  material: blue_rubber
}

triangle{
  p0{
    x: 3
    y: 3
    z: -6
  }
  p1{
    x: 3
    y: 1
    z: -6
  }
  p2{
    x: 2
    y: 2
    z: -6
  }
  material: green_rubber
}

rectangle{
  p0{
    x: -3
    y: -3
    z: -6
  }
  p1{
    x: -3
    y: -1
    z: -6
  }
  p2{
    x: -2
    y: -2
    z: -6
  }
  p3{
    x: -2
    y: -4
    z: -6
  }
  custom_material_enabled: true
  custom_material {
    color {
      r: 14
      g: 147
      b: 98
    }
    albedo {
      a0: 0.6
      a1: 0.1
      a2: 0
      a3: 0
    }
    specular_comp: 10
    refractive_index: 1
  }
}

Obj files

You can load 3D models in .obj format using the following format

  message Obj{
    required string fname = 1;
    optional MaterialType material = 2;
    optional Pos translation = 3;
    optional bool custom_material_enabled = 4 [default = false];
    optional Material custom_material = 5;
  }

Example:

obj{
  fname: "./../obj/suzanne.obj"
  translation{
    x: -1
    y: 1
    z: -5
  }
  material: pink_rubber
}

Code Overview

• The include folder contains the STB library files
• The obj folder contains sample 3D models to test the triangle mesh rendering
• The src folder contains most of the code
• The proto folder contains the proto file defining the protobuf schema (scene.proto) and the generated C++ libraries to use it in the program (scene.pb.cc & scene.pb.h)
• The scenes folder contains sample prototext files with different scenes
• The tests folder contains the gtest tests (WIP)

Classes

Render

• Main class for the raytracing
• It owns the shapes to be rendered (stored in the heap)
• It casts a ray using an origin point + a direction unit vector
• Then it checks if the ray intersects with anything in the scene
• If no object is hit, the render saves the background color as the value for that pixel
• If an object is hit, the render calculates the reflections and refractions from that object recursively by casting rays from the hit point at the reflected and refracted angles
• To calculate shadows it checks if the hit point has line of sight with the different light sources, if not it is in a shadow
  
• The final calculation is done by taking into account the Phong illumination model (ambient, diffused and specular) values and reflections and refractions hits
• The raytracing can be run in series, in parallel using OpenMP or in parallel using our own thread pool implementation
  

SceneManager

• The scene manager is in charge of reading the scene from the protobuf text file, parse it, generate the required shapes sets up the render environment and call the render class
• It can also write to text protobufs but this is not a user facing feature yet. It was implemented for learning and debugging purposes only
• It is a friend class of Render, so it can access all the private members on it

Image

• Holds & owns the image bitmap (pixels_) in the heap
• It is in charge of writing the color values to every pixel and to save the image to disk using an instance of ImageFile

Light

• Represents a point light source with a given intensity

Material

• Represents a given material with certain properties relating to its color, diffusivity, specularity, reflectivity and refractivity

Shape

• Pure virtual class to define the interface for all other shapes
• Used for dynamic polymorphism for the calculate intersection and calculate normal methods
  

Sphere

• Shape child class that represents a sphere centered around a given point, with a certain radius and material
• Since its the child of a pure virtual class it defines the relevant methods to be able to be instantiated

Triangle

• Shape child class that represents a triangle with three given points and a certain material. Similarly to sphere it implements its own intersection and normal calculation methods

Rectangle

• Shape child class made out of two triangles. Takes advantage of composition to represent a more complex shape
  

ObjLoader

• Reads and parses a .obj file and creates the respective triangles for the render (including material and an optional translation)

ImageFile

• RAII file handler for writing png image file. Opens the file in the constructor and frees the resource in the destructor

ObjFile

• RAII file handler for reading the .obj file. Opens the file in the constructor and frees the resource in the destructor

ThreadPool

• Thread pool design pattern
• Implements a queue of work packages for a pool of threads
• Threads take a task from the queue, run it and when they are finished, return the result and check if there are any more tasks in the queue to perform

License

This project is distributed under the DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE.