RFC: Shadow for directional lights

• Authors: Jian Huang

• Date: July. 2019

• Status: Approved

Abstract

Deck.gl has new basic lighting effect since 7.0, having shadow effects for directional lights can improve rendering quality.

Proposal

API

DirectionalLight class is the public interface to create shadow effects

• _shadow(Boolean): create shadow effect when set to true, default is false

New layer prop

• shadowEnabled(Boolean): when this prop is true, layer casts and renders shadows

Example

const ambientLight = new AmbientLight({
  color: [255, 255, 255],
  intensity: 1.0
});

const dirLight0 = new DirectionalLight({
  color: [255, 255, 255],
  intensity: 1.0,
  direction: [10, -20, -30],
  _shadow: true
});

const dirLight1 = new DirectionalLight({
  color: [255, 255, 255],
  intensity: 1.0,
  direction: [-10, -20, -30],
  _shadow: true
});

const lightingEffect = new LightingEffect({
  ambientLight,
  dirLight0,
  dirLight1
});
const deckgl = new Deck({
  canvas: 'my-deck-canvas',
  effects: [lightingEffect],
  layers: [
    // building layer
    new SolidPolygonLayer({
      shadowEnabled: true,
      ...
    }),
    // ground layer
    new SolidPolygonLayer({
      shadowEnabled: true,
      ...
    })
  ]
});

Workflow

• User creates LightingEffect instance which adds shadow modules into default shader modules
• LightingEffect instance is passed into deck and create shadow passes based on light directions, there is one shadow pass for each directional light, for now totally two lights are supported
• For each shadow pass, layers are rendered to a shadow map
• After all the effects are processed, there is a regular layer rendering pass, shadow maps are used to render the final shadows.

Limitations

With the current design, the user needs to create LightingEffect instance before Deck's initialization, so that the default modules can be modified before layer shaders are assembled.