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phong-lighting-rfc.md

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RFC: Phong Lighting

  • Authors: Jian Huang
  • Date: Sep. 2018
  • Status: For Review

Motivation

Lighting is an important rendering effects in deck.gl, the current lighting module has some issues.

  • Light source is duplicated in each layer
  • Only support point light source
  • Light source and material parameters are bundled together
  • Specular highlight is tinted by object color

Goals

  • Light sources are owned by scene and shared by layers
  • Support ambient, point and directional light sources
  • Separate light source and material parameters
  • Specular highlight is not tinted by object color

Proposal

Light Source

Three light source classes specify light source details for the scene

  • Ambient light
    color (vec3): color of ambient light source
    intensity (float): strenght of ambient light source
  • Point light
    color (vec3): color of point light source
    intensity(float): strenght of point light source
    position(vec3): position of point light source in world space coordinate
  • Directional light
    color(vec3): color of directional light source
    intensity(float): strenght of direcitonal light source
    direction(vec3): direction vector of directional light source

Lighting Material

LightPhongMaterial class specify phong model based lighting material details for each layer

  • ambient(float): Ambient light reflection ratio
  • diffuse(float): Diffuse light reflection ratio
  • shininess(float): Parameter to control specular highlight radius
  • specularColor(vec3): Color applied to specular lighting

Lighting Effect

LightingEffect class holds and manages all the light sources

  • lightSources(object): all the light sources in the scene

New Deck Prop

  • effects(array): input of all the rendering effects in the scene

New Layer Prop

  • material(object): input of lighting material attached to the layer

Outdated Layer Prop

  • lightSettings(object)

Lighting Model

Blinn phong model will be implemented in the shader module to calculate the actual light weight

Code Example

Create light sources

const directionalLight = new DirectionalLight( 0xffffff, 0.5, [1, 0, 0]);
const pointLight = new PointLight( 0xffffff, 0.5, [0, 0, 0]);

Create lighting effect

const lightingEffect = new LightingEffect({pointLight, directionalLight}])

Create material

const phongMeterial = new LightPhongMeterial(0.3, 0.5, 32, [255, 255, 255, 255])

Create deck and layer

const deck = new Deck({
 effects: [lightingEffect],
 layers: [
   new GeoJsonLayer({
     data: US_MAP_GEOJSON,
     stroked: true,
     filled: true,
     getLineColor: [255, 100, 100],
     getFillColor: [200, 160, 0, 180],
     material:phongMeterial
     }
   })
 ]});

Next Step

PBR Lighting

Lighting implemented with PBR models