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VBA Raymarcher

About The Project

This is a small simplistic Raymarcher implementation based on Microsoft Excel's VBA interface. The algorithm traces three-dimensional objects using their implicit function definitions. Currently, only spheres and cuboids are supported, but the framework provides an interface for the definition of additional shapes.

The project also includes a small demo that showcases all available features.

Getting Started

This is a short explanation on how to run the Raymarcher yourself.

Demo

The folder demo contains the Excel document main.xlsb. This project can simply be opened in Microsoft Excel for a short demonstration of the features. Please keep in mind that Excel will first require the permission to run VBA code downloaded from unknown sources.

Installation

Should you instead want to run the raytracer in your own Excel documents, first create the new Excel document (be careful to select the type "Excel Document WITH Macros"). Then, you will have to import all modules and class modules provided in the src folder into the new project. You can do this in Excel's VisualBasic screen under File -> Import File. The imported modules can now be accessed from any other code file in the project.

Usage

The Raytracer class represents the main actor responsible for the process. Upon creating a new instance of the class, the new object will be populated with default values as defined in src/class-modules/Raytracer.cls. At runtime, these default values can be changed to modify the behaviour of the raytracer. A new raytracer can also be created using the CreateRaycaster(...) function provided in src/modules/utils.bas.

The main properties that can be modified are

  • cam: The camera, from which the tracing process is started. It is defined as an instance of the ViewerCamera class, which is a simple data structure defining the viewer's viewing direction, their "up" direction and their position in the world.

  • world: The observable world traced by the raytracer. It is a collection of shapes (as instances of the WorldSpaceShape interface) and lights (as instances of the Light class). The world object is responsible for the calculation of the distance between a point and all objects it contains, as is required by the raymarching procedure.

  • far: The maximum distance from the camera that will be inspected by the raytracer.

  • planeDistance: The distance between the camera and the view-plane, onto which the world will be projected.

  • pixelWidth / pixelHeight: The height in pixels for the output image of the procedure.

  • planeWidth / planeHeight: The dimensions of the view-plane, onto which the world will be projected.

  • backgroundColour: The colour of the background, given as a VBA Long value, used in case no intersection with the world can be found for some pixel.

After setting up the Raytracer object, the method Raytracer.run() can be used to start the procedure. The method will return a two-dimensional array containing the colour values of every pixel of the output image. This result can then be displayed in Excel similarly to the approach used in the demo.

WorldSpaceShape

Instances of the WorldSpaceShape interface represent objects in the world. Currently, simple implementations for cuboids and spheres are provided, but additional shapes can be defined using the same interface. Classes implementing this interface must define the properties:

  • specularReflection As Double
  • diffuseReflection As Double
  • ambientReflection As Double
  • shininess As Double
  • colour As Long

These properties are used in the illumination computation to determine the colour of the object. The three reflection values are factors that determine the influence of specular, diffuse and ambient lighting on this object. The shininess property defines the strength of shiny reflection where light othogonally touches the surface. The colour value is a colour code for the colour of the object (currently, only even-coloured objects are supported. Multiple different colours cannot be used on the same shape).

Furthermore, the WorldSpaceShape interface defines the method Function Distance(p As Vector3) As Double. For any given point, this function returns its distance to the shape.

Instances of classes that implement this interface can be passed to the world object using the method WorldSpace.AddShape(shape as WorldSpaceShape).

License

This project is distributed under the MIT License (See LICENSE.txt for more information).