Rendering

Rendering a scene needs the following ingredients:

hdrimg holds the HDR image data.
AbstractCamera object defines the camera parameters.
PCG is a pseudo-random number generator used for integration and sampling.
renderer is an instance of Function that take World and optionally a PCG object, instructing on how a ray should be traced through the scene.
ImageTracer is a function that takes the hdrimg, AbstractCamera, and renderer (and optionally a PCG) to render the scene.

First we need to create an hdrimg object to hold the rendered image data. The hdrimg constructor takes the width and height of the image as parameters.

jujutracer.hdrimg — Type

struct hdrimg(w::Int, h::Int)

A struct representing a high dynamic range image (HDR image). Getter and setter methods are defined for accessing and modifying pixel values. Access is done using 0-based indexing, so the first pixel is at (0, 0): img[0, 0]; while the bottom right pixel is at (w-1, h-1): img[w-1, h-1].

    img = [ (0  , 0)   (0  , 1) ... (0  , w-1)
            (1  , 0)   (1  , 1) ... (1  , w-1)
             ...
            (h-1, 1)   (h-1, 2) ... (h-1, w-1) ]

Fields

img::Matrix{RGB}: A matrix of RGB values representing the HDR image. Not intedend to be accessed directly.
w::Int64: The width of the image in pixels.
h::Int64: The height of the image in pixels.

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The we can set the camera. We have two types of cameras: Perspective and Orthogonal, both subtypes of AbstractCamera.

jujutracer.Perspective — Type

Perspective

Perspective camera type

Fields

t::Transformation the transformation related to the camera's standing
a_ratio::Float64 aspect ratio of the screen of the camera

Constructor

Perspective() creates a perspective camera with Identity Transformation, a 16:9 aspect ratio placed in (-1, 0, 0)
Perspective(d = dist, t = trans, a_ratio = a) creates a perspective camera with trans Transformation, an a aspect ratio placed in (-d, 0, 0)

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jujutracer.Orthogonal — Type

Orthogonal

Orthogonal camera type

Fields

t::Transformation the transformation related to the camera's standing
a_ratio::Float64 aspect ratio of the screen of the camera

Constructor

Orthogonal() creates an orthogonal camera with Identity Transformation and a 16:9 aspect ratio
Ortoghonal(t = trans, a_ratio = a) creates an orthogonal camera with trans Transformation and an a aspect ratio

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A PCG object is used for pseudo-random number generation.

jujutracer.PCG — Type

mutable struct PCG

A Pseudo-Random Number Generator (PRNG) based on the PCG algorithm.

Fields

state::UInt64: The current state of the PCG. It is atomically wrapped to ensure thread safety.
inc::UInt64: The increment value used in the PCG algorithm.

Constructor

PCG(init_state::UInt64, init_seq::UInt64): Creates a new PCG instance with the given initial state and sequence. Defaults are 42 and 54 respectively.

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Renderers

We have several renderers available, each with different complexity and quality.

jujutracer.OnOff — Type

OnOff(world::World)

OnOff renderer of the scene. Returns white if the ray hits something, balck otherwise

Fields

world::World the world containing the scene
background_color::RGB the color of the background when the ray doesn't hit anything
foreground_color::RGB the color of the foreground when the ray hits something

Functional Usage

OnOff(ray::Ray) functional renderer on a ray

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jujutracer.Flat — Type

Flat(world::World)

Flat renderer of the scene. Returns the Emition pigment of the hitten shapes

Fields

world::World the world containing the scene

Functional Usage

Flat(ray::Ray) functional renderer on a ray

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jujutracer.PathTracer — Type

PathTracer(world::World, backg::RGB, rnd::PCG, n_rays::Int64, depth::Int64, russian::Int64)

Path Tracer renderer of the scene.

Fields

world::World: the world containing the scene
backg::RGB: the background color when the ray doesn't intersect anything
rnd::PCG: the random number generator
n_rays::Int64: the number of rays fired from the hitten point
depth::Int64: the maximum depth to be reached by a ray
russian::Int64: number of iteration before playing with Russian Roulet

Functional Usage

PathTracer(ray::Ray) functional renderer on a ray

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jujutracer.PointLight — Type

PointLight(world::World, background::RGB, ambient::RGB, max_depth::Int64)

PointLight renderer of the scene. Backtraces the light from the point light sources.

Fields

world::World: the world containing the scene. Must contain at least one light source
background_color::RGB: the color of the background when the ray doesn't hit anything
ambient_color::RGB: the ambient color of the scene
max_depth::Int64: the maximum depth of the ray tracing

Functional Usage

PointLight(ray::Ray) functional renderer on a ray

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Rendering process

The rendering process is initiated by calling the ImageTracer on a hdrimage. Optionally, a PCG object can be passed to the ImageTracer for antialising and stratified sampling.

jujutracer.ImageTracer — Type

struct ImageTracer

Convenient struct to hold the hdrimage and the camera.

Fields

img::hdrimg: The HDR image to be traced.
camera::AbstractCamera: The camera used for tracing rays. Can be either Orthogonal or Perspective.

Constructor

ImageTracer(): Creates a new ImageTracer with a default HDR image and an orthogonal camera.
ImageTracer(img::hdrimg, camera::AbstractCamera): Creates a new ImageTracer with the specified HDR image and camera.

Functional Usage

ImageTracer(fun::Function): tracing the image with fun renderer.
ImageTracer(fun::Function, AA::Int64, pcg::PCG): tracing the image with fun renderer and Anti-Aliasing method with AA^2 subdivision in the pixel.

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Saving

jujutracer provides functions to save the rendered image boht in HDR and LDR formats.

jujutracer.write_pfm_image — Function

write_pfm_image(img::hdrimg, io, endianness::Bool=true)

Write a PFM file encodiding the content of an hdrimg

Arguments

img::hdrimg: The HDR image to be written to the PFM file.
io::IO: The output stream to which the PFM image will be written.
endianness::Bool: A boolean indicating whether to write the float values in little-endian format (default is true).

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write_pfm_image(img::hdrimg, filename::String, endianness::Bool=true)

Write a PFM file encoding the content of an hdrimg.

Arguments

img::hdrimg: The HDR image to be written to the PFM file.
filename::String: The file path where the PFM image will be saved, including the ".pfm" extension.
endianness::Bool: A boolean indicating whether to write the float values in little-endian format (default is true).

Raises

InvalidFileFormat: If the file extension is not ".pfm".

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jujutracer.tone_mapping — Function

tone_mapping(img::hdrimg; a=0.18, lum = nothing, γ = 1.0)

Apply tone mapping to the HDR image.

Arguments

img::hdrimg: The HDR image to be tone-mapped.
a::Float64: A positive value to be used in the normalization formula (default is 0.18).
lum::Float64: The average luminosity of the image. If not provided, it will be calculated using _average_luminosity.
γ::Float64: The gamma value to be used for correction. Must be a positive number (default is 1.0).

Returns

hdrimg: The tone-mapped HDR image.

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jujutracer.get_matrix — Function

get_matrix(img::hdrimg)

Extract the matrix from an HDR image.

Arguments

img::hdrimg: The HDR image from which to extract the matrix.

Returns

Matrix: The matrix representation of the HDR image.

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jujutracer.save_ldrimage — Function

save_ldrimage(img_matrix::Matrix, filename::String)

Save an LDR image to a file.

Arguments

img_matrix::Matrix: The matrix representation of the image to be saved.
filename::String: The name of the file to save the image to, including the file extension (".png" or ".jpg").

Returns

String: The path to the saved file.

Raises

ArgumentError: If the file extension is not valid or if the image values are not clamped.

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