Scene Configuration

Camera

The Perspective View Camera Model

Fields:

• lookfrom - Position of the Camera in 3D World Space
• lookat - Point in the 3D World Space where the Camera is Pointing
• vfov - Field of View of the Camera
• focus - The focal length of the Camera
• fixedparams - An instance of FixedCameraParams

Available Constructors:

• Camera(;lookfrom = Vec3(0.0f0), lookat = Vec3(0.0f0), vup = Vec3(0.0f0, 1.0f0, 0.0f0), vfov = 90.0f0, focus = 1.0f0, width = 128, height = 128)
• Camera(lookfrom::Vec3{T}, lookat::Vec3{T}, vup::Vec3{T}, vfov::R, focus::R, width::Int, height::Int) where {T<:AbstractArray, R<:Real}

FixedCameraParams

The Parameters of the Camera which should not be updated in inverse rendering are wrapped into this object.

Fields:

• vup - Stores the World UP Vector (In most cases this is the Y-Axis Vec3(0.0, 1.0, 0.0))
• width - Width of the image to be rendered
• height - Height of the image to be rendered

compute_screen_coordinates(c::Camera, film_aperture::Tuple,
                           inch_to_mm::Real = 25.4)

Computes the coordinates of the 4 corners of the screen and returns top, right, bottom, and left.

get_primary_rays(c::Camera)

Takes the configuration of the camera and returns the origin and the direction of the primary rays.

get_transformation_matrix(c::Camera)

Returns the camera_to_world transformation matrix. This is used for transforming the coordinates of a Point in 3D Camera Space to 3D World Space using the camera2world function.

DistantLight

A source of light that is present at infinity as such the rays from it are in a constant direction. The intensity for this light source always remains constant. This is extremely useful when we are trying to render a large scene like a city.

Fields:

• color - Color of the Light Rays emitted from the Source.
• intensity - Intensity of the Light Source.
• direction - Direction of the Light Rays emitted by the Source.

Available Constructors:

• DistantLight(;color = Vec3(1.0f0), intensity::Real = 1.0f0, direction = Vec3(0.0f0, 1.0f0, 0.0f0))
• DistantLight(color, intensity::Real, direction)

Light

All objects emitting light should be a subtype of this. To add a custom light source, two only two functions need to be defined.

• get_direction(l::MyCustomLightSource, pt::Vec3) - pt is the point receiving the light from this source
• get_intensity(l::MyCustomLightSource, pt::Vec3, dist::Array) - dist is the array representing the distance of the point from the light source

PointLight

A source of light which emits light rays from a point in 3D space. The intensity for this light source diminishes as inverse square of the distance from the point.

Fields:

• color - Color of the Light Rays emitted from the source.
• intensity - Intensity of the Light Source. This decreases as $\frac{1}{r^2}$ where $r$ is the distance of the point from the light source.
• position - Location of the light source in 3D world space.

Available Constructors:

• PointLight(;color = Vec3(1.0f0), intensity::Real = 100.0f0, position = Vec3(0.0f0))
• PointLight(color, intensity::Real, position)

get_direction(l::Light, pt::Vec3)

Returns the direction of light incident from the light source to pt.

get_intensity(l::Light, pt::Vec3, dist::Array)

Computed the intensity of the light ray incident at pt.

get_shading_info(l::Light, pt::Vec3)

Returns the direction of light incident from the light source onto that Point and the intensity of that light ray. It computes these by internally calling the get_direction and get_intensity functions and hence this function never has to be modified for any Light subtype.

Arguments:

• l - The Object of the Light subtype
• pt - The Point in 3D Space for which the shading information is queried

Material

This Type stores information about the material of an Object. We compute the color of a point by dispatching on the type of the material. That is why we store nothing when a particular field is absent.

Fields:

• color_ambient - The Ambient Color of the Material.
• color_diffuse - The Diffuse Color of the Material.
• color_specular - The Specular Color of the Material.
• specular_exponent - Specular Exponent of the Material.
• reflection - The reflection coefficient of the material.
• texture_ambient - Stores the ambient texture image (if present) in Vec3 format.
• texture_diffuse - Stores the diffuse texture image (if present) in Vec3 format.
• texture_specular - Stores the specular texture image (if present) in VEc3 format.
• uv_coordinates - The uv coordinates are stored as a vector (of length 3) of tuples.

Available Constructors

Material(;color_ambient = Vec3(1.0f0), color_diffuse = Vec3(1.0f0),
          color_specular = Vec3(1.0f0), specular_exponent::Real = 50.0f0,
          reflection::Real = 0.5f0, texture_ambient = nothing, 
          texture_diffuse = nothing, texture_specular = nothing,
          uv_coordinates = nothing)

get_color(m::Material, pt::Vec3, ::Val{T}, obj::Object)

Returns the color at the point pt. We use T and the type of the Material m for efficiently dispatching to the right function. The right function is determined by the presence/absence of the texture field. The possible values of T are :ambient, :diffuse, and :specular.

reflection(m::Material)

Returns the reflection coefficient of the Material m.

specular_exponent(m::Material)

Returns the specular_exponent of the Material m.

Sphere

Sphere is a primitive object.

Fields:

• center - Center of the Sphere in 3D world space
• radius - Radius of the Sphere
• material - Material of the Sphere

Triangle

Triangle is a primitive object. Any complex object can be represented as a mesh of Triangles.

Fields:

• v1 - Vertex 1
• v2 - Vertex 2
• v3 - Vertex 3
• material - Material of the Triangle

load_obj(file; outtype = Float32)

Parser for obj file. It returns a set of Triangles that make up the scene.

Only the following things are parsed as of now: v, vt, vn, f, usemtl and mtllib.

parse_mtllib!(file, material_map, outtype)

Parses .mtl file and creates a map from the material name to Material objects.

Not all fields of the mtl file are parsed. We only parse : newmtl, Ka, Kd, Ks, Ns, d, Tr, map_Kd, map_Ks, and map_Ka.

triangulate_faces(vertices::Vector, texture_coordinates::Vector,
                  faces::Vector, material_map::Dict)

Triangulates the faces and converts it into valid Triangle objects.

Object

All primitive objects must be a subtype of this. Currently there are two primitive objects present, Triangle and Sphere. To add support for custom primitive type, two functions need to be defined - intersect and get_normal.

intersect(obj::Object, origin, direction)

Computes the intersection of the light ray with the object. This function returns the $t$ value where $intersection\_point = origin + t \times direction$. In case the ray does not intersect with the object Inf is returned.

get_color(obj::Object, pt::Vec3, sym::Val)

Computes the color at the point pt of the Object obj by dispatching to the correct get_color(obj.material, pt, sym, obj) method.

get_normal(obj::Object, pt, direction)

Returns the normal at the Point pt of the Object obj.

reflection(obj::Object)

Returns the reflection coefficient of the material of the Object.

specular_exponent(obj::Object)

Returns the specular_exponent of the material of the Object.