camera.js

const Signal = require('signals')
const mat4 = require('pex-math/mat4')
const vec3 = require('pex-math/vec3')

function Camera(opts) {
  const gl = opts.ctx.gl
  this.type = 'Camera'
  this.projection = opts.projection || 'perspective'
  this.enabled = true
  this.changed = new Signal()

  this.near = 0.1
  this.far = 100
  this.aspect = 1
  this.exposure = 1

  this.viewMatrix = mat4.create()
  this.inverseViewMatrix = mat4.create()

  this.focalLength = 50 // mm
  this.fStop = 2.8

  this.sensorSize = [36, 24] //mm
  this.actualSensorHeight = 24 //mm
  this.sensorFit = 'vertical'

  if (this.projection === 'perspective') {
    this.fov = Math.PI / 4

    this.projectionMatrix = mat4.perspective(
      mat4.create(),
      this.fov,
      this.aspect,
      this.near,
      this.far
    )
  } else if (this.projection === 'orthographic') {
    this.left = -1
    this.right = 1
    this.bottom = -1
    this.top = 1
    this.zoom = 1

    this.projectionMatrix = mat4.ortho(
      mat4.create(),
      this.left,
      this.right,
      this.bottom,
      this.top,
      this.near,
      this.far
    )
  }

  this.viewport = [0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight]
  this.view = null

  this.set(opts)
}

Camera.prototype.init = function(entity) {
  this.entity = entity
}

Camera.prototype.set = function(opts) {
  Object.assign(this, opts)

  if (opts.viewport) {
    this.aspect = this.viewport[2] / this.viewport[3]
    const postProcessingCmp =
      this.entity && this.entity.getComponent('PostProcessing')
    if (postProcessingCmp) {
      postProcessingCmp.set({
        viewport: this.viewport,
        viewMatrix: this.viewMatrix
      })
    }
  }

  // calculate new fov based on sensor size and focal length
  if (
    opts.sensorSize ||
    opts.sensorFit ||
    opts.focalLength ||
    opts.viewport ||
    opts.fov
  ) {
    let sensorWidth = this.sensorSize[0]
    let sensorHeight = this.sensorSize[1]
    const sensorAspectRatio = sensorWidth / sensorHeight
    if (this.aspect > sensorAspectRatio) {
      if (this.sensorFit === 'horizontal' || this.sensorFit === 'fill') {
        sensorHeight = sensorWidth / this.aspect
      }
    } else {
      //this.aspect <= sensorAspectRatio
      if (this.sensorFit === 'horizontal' || this.sensorFit === 'overscan') {
        sensorHeight = sensorWidth / this.aspect
      }
    }
    if (opts.fov) {
      this.focalLength = sensorHeight / 2 / Math.tan(this.fov / 2)
    } else {
      this.fov = 2 * Math.atan(sensorHeight / 2 / this.focalLength)
    }
    this.actualSensorHeight = sensorHeight
  }

  if (
    this.projection === 'perspective' &&
    (opts.aspect ||
      opts.near ||
      opts.far ||
      opts.fov ||
      opts.view ||
      opts.viewport ||
      opts.sensorSize ||
      opts.sensorFit ||
      opts.focalLength)
  ) {
    if (this.view) {
      const aspectRatio = this.view.totalSize[0] / this.view.totalSize[1]

      const top = Math.tan(this.fov * 0.5) * this.near
      const bottom = -top
      const left = aspectRatio * bottom
      const right = aspectRatio * top
      const width = Math.abs(right - left)
      const height = Math.abs(top - bottom)
      const widthNormalized = width / this.view.totalSize[0]
      const heightNormalized = height / this.view.totalSize[1]

      const l = left + this.view.offset[0] * widthNormalized
      const r =
        left + (this.view.offset[0] + this.view.size[0]) * widthNormalized
      const b =
        top - (this.view.offset[1] + this.view.size[1]) * heightNormalized
      const t = top - this.view.offset[1] * heightNormalized

      mat4.frustum(this.projectionMatrix, l, r, b, t, this.near, this.far)
    } else {
      mat4.perspective(
        this.projectionMatrix,
        this.fov,
        this.aspect,
        this.near,
        this.far
      )
    }
  } else if (
    this.projection === 'orthographic' &&
    (opts.left ||
      opts.right ||
      opts.bottom ||
      opts.top ||
      opts.zoom ||
      opts.near ||
      opts.far ||
      opts.view)
  ) {
    const dx = (this.right - this.left) / (2 / this.zoom)
    const dy = (this.top - this.bottom) / (2 / this.zoom)
    const cx = (this.right + this.left) / 2
    const cy = (this.top + this.bottom) / 2

    let left = cx - dx
    let right = cx + dx
    let top = cy + dy
    let bottom = cy - dy

    if (this.view) {
      const zoomW = 1 / this.zoom / (this.view.size[0] / this.view.totalSize[0])
      const zoomH = 1 / this.zoom / (this.view.size[1] / this.view.totalSize[1])
      const scaleW = (this.right - this.left) / this.view.size[0]
      const scaleH = (this.top - this.bottom) / this.view.size[1]

      left += scaleW * (this.view.offset[0] / zoomW)
      right = left + scaleW * (this.view.size[0] / zoomW)
      top -= scaleH * (this.view.offset[1] / zoomH)
      bottom = top - scaleH * (this.view.size[1] / zoomH)
    }

    mat4.ortho(
      this.projectionMatrix,
      left,
      right,
      bottom,
      top,
      this.near,
      this.far
    )
  }

  Object.keys(opts).forEach((prop) => this.changed.dispatch(prop))
}

Camera.prototype.getViewRay = function(x, y, windowWidth, windowHeight) {
  if (this.view) {
    x += this.view.offset[0]
    y += this.view.offset[1]
    windowWidth = this.view.totalSize[0]
    windowHeight = this.view.totalSize[1]
  }
  let nx = (2 * x) / windowWidth - 1
  let ny = 1 - (2 * y) / windowHeight

  let hNear = 2 * Math.tan(this.fov / 2) * this.near
  let wNear = hNear * this.aspect

  nx *= wNear * 0.5
  ny *= hNear * 0.5

  let origin = [0, 0, 0]
  let direction = vec3.normalize([nx, ny, -this.near])
  let ray = [origin, direction]

  return ray
}

Camera.prototype.update = function() {
  mat4.set(this.inverseViewMatrix, this.entity.transform.modelMatrix)
  mat4.set(this.viewMatrix, this.entity.transform.modelMatrix)
  mat4.invert(this.viewMatrix)
}

module.exports = function createCamera(opts) {
  return new Camera(opts)
}