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Core Systems

🚧 this page is currently under construction! 🚧

The main Echo.Core is composed of seven major systems, each contributing a different purpose towards to the goal of synthesizing photorealistic images. These systems occupy various namespaces under Echo.Core and are catalogued below in order of relative importance.

Table of Contents
  1. Evaluation
  2. Aggregation
  3. Processes
  4. Scenic
  5. Textures
  6. Common
  7. In Out

Evaluation

The Echo.Core.Evaluation namespace contains systems related to the evaluation of a Scene (many evaluations are composited together to create a render). Besides aggregation, this namespace occupies the majority of the runtime during rendering. Its systems are listed here:

  • An Evaluator defines how a Scene is evaluated. It takes in a PreparedScene and a Ray, then returns a corresponding Float4 which represents the evaluated data. The PathTracedEvaluator does exactly as its name suggests; it evaluates the Scene using path tracing with multiple importance sampling and next-event estimation. A simpler evaluator is the BruteForcedEvaluator, which implements the naive recursive path tracing algorithm; it is sometimes used as a reference evaluator. Besides evaluators, there is also EvaluatorStatistics that features a very lightweight statistics capture system and is mainly used by the PathTracedEvaluator.
  • A Material defines the physical properties of a geometric surface when it interacts with light. In the current version of Echo, each Material can produce one or more BxDFs (described below) upon a Ray interaction. All materials are presented with more detail in Materials.
  • To support sampling techniques such as multiple importance sampling, Echo implements various distributions which can easily sampled from. Normally, a Sample1D is first drawn from a ContinuousDistribution (a Sample1D is just a number >= 0 and < 1), and then used to sample a DiscreteDistribution1D, or select from some other source. Note that Echo evaluates the Scene in epochs, and the size of each epoch is precisely the value of Extend in the ContinuousDistribution. This is also why EvaluationProfile uses MinEpoch and MaxEpoch, and why number of samples per pixel is Extend * Epoch.
  • All light scattering behavior are contained in various BxDF implementations. BxDF stands for bidirectional X distribution function, where the X can be either reflective or transmissive. A set of BxDF is created and stored in a BSDF when a ray interacts with a surface, and that BSDF wraps the functionality of the containing BxDF. Note that all BxDF calculation are done in local space of the surface, where the surface normal points in the positive Z direction. Additionally, an outgoing direction points from the point of interaction towards the camera, while an incoming direction points towards the light.

Aggregation

The Echo.Core.Aggregation namespace manages spatial calculations done on the Scene. This mainly includes the Ray-Scene intersection testing and light picking.

  • An Accelerator improves the speed of
  • Light selection
  • Preparation

Processes

The Echo.Core.Processes namespace oversees the entire rendering process using Operations; it handles the full lifecycle of a render, containing the following three stages.

  • Preparation
  • Evaluation
  • Composition

Scenic

The Echo.Core.Scenic namespace has the necessary components to building a Scene.

  • Geometric objects
  • Lights
  • Instancing
  • Preparation

Textures

The Echo.Core.Textures namespace defines various implementations of Textures, which are 2D planes that can be samples at arbitrary coordinates to get colors.

  • Colors
  • Textures
  • Directional

Common

The Echo.Core.Common namespace

  • Compute
  • Mathematics
  • Packed

In Out

The Echo.Core.InOut namespace

  • Echo Description
  • Images
  • Models