glsl-proj4

glsl-proj4

proj4 implementation for glsl

implemented projections:

• aea - albers equal area
• geocent - geocentric (ecef) coordinates
• gnom - gnomic projection
• lcc - lambert conformal conic
• ortho - ortho
• tmerc - transverse mercator

example

var regl = require('regl')()
var camera = require('regl-camera')(regl, { distance: 10 })
var glsl = require('glslify')

var proj = require('glsl-proj4')
var p = proj('+proj=aea +lat_1=16 +lat_2=24 +lat_0=19 +lon_0=-157 +x_0=0 +y_0=0'
  + '+ellps=GRS80 +datum=NAD83 +units=m +no_defs')

var mesh = require('./hawaii.json')
var draw = regl({
  frag: `
    precision highp float;
    void main () {
      gl_FragColor = vec4(0.5,0.5,0.5,1);
    }
  `,
  vert: glsl`
    precision highp float;
    #pragma glslify: forward = require('glsl-proj4/aea/forward')
    #pragma glslify: proj_t = require('glsl-proj4/aea/t')
    uniform proj_t proj;
    uniform float aspect;
    attribute vec2 position;
    void main () {
      vec3 p = forward(proj, position)*vec3(1,aspect,1);
      gl_Position = vec4(p*1e-6,1);
    }
  `,
  attributes: {
    position: mesh.positions
  },
  uniforms: Object.assign(p.members('proj'), {
    aspect: function (context) {
      return context.viewportWidth / context.viewportHeight
    }
  }),
  elements: mesh.cells
})
regl.frame(function () {
  regl.clear({ color: [1,1,1,1], depth: true })
  draw()
})

javascript api

var proj = require('glsl-proj4')

var p = proj(str)

Create a proj instance p from a proj4 string str.

p.members(name)

Return an object that maps member keys under the prefix name to values. You can pass this object as a struct uniform.

If name is not provided, no prefix is used.

p.update(str)

Update the projection string.

p.name

String name of the projection.

glsl api

#pragma glslify: aea_t = require('glsl-proj4/aea/t')
#pragma glslify: aea_forward = require('glsl-proj4/aea/forward')
#pragma glslify: aea_inverse = require('glsl-proj4/aea/inverse')

#pragma glslify: geocent_t = require('glsl-proj4/geocent/t')
#pragma glslify: geocent_forward = require('glsl-proj4/geocent/forward')
#pragma glslify: geocent_inverse = require('glsl-proj4/geocent/inverse')

#pragma glslify: gnom_t = require('glsl-proj4/gnom/t')
#pragma glslify: gnom_forward = require('glsl-proj4/gnom/forward')
#pragma glslify: gnom_inverse = require('glsl-proj4/gnom/inverse')

#pragma glslify: lcc_t = require('glsl-proj4/lcc/t')
#pragma glslify: lcc_forward = require('glsl-proj4/lcc/forward')
#pragma glslify: lcc_inverse = require('glsl-proj4/lcc/inverse')

#pragma glslify: ortho_t = require('glsl-proj4/ortho/t')
#pragma glslify: ortho_forward = require('glsl-proj4/ortho/forward')
#pragma glslify: ortho_inverse = require('glsl-proj4/ortho/inverse')

#pragma glslify: tmerc_t = require('glsl-proj4/tmerc/t')
#pragma glslify: tmerc_forward = require('glsl-proj4/tmerc/forward')
#pragma glslify: tmerc_inverse = require('glsl-proj4/tmerc/inverse')

vec3 proj_foward(proj_t t, vec3 pt)

Forward project pt using the parameters from t.

vec3 proj_foward(proj_t t, vec2 pt)

Forward project pt using the parameters from t with an altitude of 0.

vec3 proj_inverse(proj_t t, vec3 pt)

Inverse project pt using the parameters from t.

vec3 proj_inverse(proj_t t, vec2 pt)

Inverse project pt using the parameters from t and an altitude of 0.

install

npm install glsl-proj4

license

BSD

Parts of this library were adapted from proj4js.