RT

RT (Ray tracer) is a mile-stone project in the 3D graphics curriculum of 42.

We're a team of four who've realized this project by combing a series of modules and features to make a pretty fun ray tracer. This includes :

• anti-aliasing
• Perlin noise
• constructive solid geometry
• multi-threading
• soft shadows
• Phong shading
• tone mapping
• color quantization (for an 8-bit effect)
• reflection/refraction
• volume hierarchy
• textures
• wavefront obj rendering

This document will explain : 1. How to write scenes using our custom scene description syntax more or less based on JSON. 2. The global variables which affect how the scene is rendered.

Compatibility

RT has so far only been tested on Mac Mavericks through Yosemite. You will need to install SDL.

Take Off

make
./rt ./example.rtsdf

.rtsdf - Ray Tracing Description File

A complete scene will have the following Elements specified by the user:

Window
Camera
Light
Shapes

Characteristics of parser

• Single line comments are possible and use c++ style // and must be placed at beginning of line to function
• Scene elements and sub Elements begin with a capital letter
  • Their fields are balenced with {}
  • Scalars are contained in <>
  • Vectors are contained in <,,> and their values are comma separated.

Window

The Window element defines an SDL window. One can specify its width and height .

example :

Window {
	width <1000>
	height <600>
}

Camera

The Camera is a point camera from where rays will originate but other aspects of the scene may be described here. Its fields are : fov (the camera's field of view), origin, direction, anti_aliasing, sh_grain (the graininess of the soft shadows) . It accepts the sub-elements Transformation and Film.

example :

Camera {
	fov <50>
	origin <0, 0, 0>
	direction <0, 0, 1>
	//Boolean 0 or 1 - the amount is defined in
	//a header, explained below
	anti_aliasing <1>
	//An integer between 1 and 100
	sh_grain <1>
	Film {
		...
	}
	Transformation	{
		...
	}
}

Film

One can apply a few effects to the rendered image by specifying the fields: ldr - (Low Dynamic Range) which tonemaps the image quantize - Produces an 8-bit effect by reducing the color range and looking for the nearest-neighbor. exposure - increase image's brightness

example :

Film {			
	ldr <1> //bool
	quantize <1> //bool
	exposure <1.4>//double between ~0 and 3
}

Transformation

Transformation combines the scale, rotation and transformation vectors to generate a transformation matrix. Can be applied to shapes, Camera and Light elements.

example :

Transformation {
	scale <3, 3, 3>
	rotation <0, 0, 0>
	translation <0, 10, -10>
}

Lights

A scene can have a maximum of two lights. RT uses naive point-lights. One can specify a light's Transformation and color.

example :

Light {
	//rgb values
	color <255, 255, 255>
	Transformation {
		scale <3, 3, 3>
		rotation <0, 0, 0>
		translation <0, 0, 0>
	}
}

Shapes

Accepts sub-elements Transformation and Material.

Primitives

RT renders the primitives Plane, Sphere, Cylinder, Cone, Triangle and Cube.

example :

Cylinder {
	Transformation {
		...
	}
	Material {
		...
	}
}

Mesh

RT can render wavefront obj models by specifying its path.

example:

Mesh {
 	url "./standfordBunny.obj"
	Transformation {
		...
	}
	Material {
		...			
	}
}

Constructive-Solid Geometry (csg)

A Csg is constructed by recursively associating the primitives Sphere, Plane , Cylinder or Cone with the either a Difference, Union or Intersection operator inside a manually specified tree via the Left and Right fields.

Example :

Csg {
	Difference {
		Left {
			Sphere {
				...
				}
				Material {
					...
				}
			}
		}
		Right {
			Cylinder {
				Transformation {
					...
				}
				Material {
					...
			}
		}
	}
}

Materials

A user may specify an object's color, Phong-shading coefficients : lambert, specular, ambient, and the amount of refraction/reflective.

Under Material, one can specify a Texture.

example:

Material
{
	color <130, 155, 95>
	//doubles between 0 and 1
	lambert <.6>
	specular <.2>
	ambient <.2>
	reflective <0.3>
	refraction <0.2>
	Texture {
		...
	}
}

Textures

RT can apply bitmap files and Perlin-noise as textures.

Bitmap Textures

example:

Texture {
	//looks for 'starry_night' in '../textures/'
	type "extern"
	file "starry_night"
}

Perlin Noise

Via the type field, one can specify three different Perlin noise presets : "pure", "marble" and "wood".

In all cases, the two colors between which the noise fluctuates, the repetition factor on each axis, the noise turbulence's power and size, can be specified via the fields color_a/color_b, repetition, turb_power and turb_size respectively.

example :

Texture {
	type "marble"
	color_a <255, 255, 255>
	color_b <0, 0, 0>
	repetition <0.3, 0.3, 0.3>
	turb_power <64>
	turb_size <16>
}

Modifying program behavior in Headers

All of the variables which modify key program behavior can be edited from include/macros.h

Anti Aliasing

Number of samples per pixel from the default four.

# define AA_SAMPLES 4

Multi-threading

Number of threads to run.

# define NTHREAD 1