glsl-proj4-camera

use proj4 strings to map lonlat geometry to screen coordinates in a shader

This module sets up listeners for mouse events to update the member uniforms
given in a proj4 string.

example

view this demo

`` js
var regl = require('regl')()
var glsl = require('glslify')
var camera = require('glsl-proj4-camera')(location.hash.replace(/^#/,'') ||
+proj=tmerc +lat_0=18.83333333333333 +lon_0=-155.5 +ellps=GRS80 +units=m
+k_0=0.0000019268500651226404 +x_0=0.35589838645697514
+y_0=-0.34185734540971613.trim())

camera.on('update', function () {
location.hash = camera.string()
})

var mesh = require('./hawaii.json')
var draw = regl({
frag:
precision mediump float;
void main () {
gl_FragColor = vec4(0.5,0.5,0.5,1);
}
,
vert: glsl
precision mediump float;
#pragma glslify: forward = require('glsl-proj4/tmerc/forward')
#pragma glslify: proj_t = require('glsl-proj4/tmerc/t')
uniform proj_t proj;
attribute vec2 position;
uniform float aspect;
void main () {
vec3 p = forward(proj, position)*vec3(1,aspect,1);
gl_Position = vec4(p,1);
}
,
attributes: {
position: mesh.positions
},
uniforms: Object.assign(camera.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()
})
`

api

` js
var projcamera = require('glsl-proj4-camera')
`

var camera = projcamera(str)

Create a camera instance from a proj4 string str.

var uniforms = camera.members(name)

Return an object of dotted uniform members from a prefix name.

var str = camera.string()

Return a proj4 string for the current view.

camera.on('update', function (members) {})

When the map view changes, this event fires.

install

`
npm install glsl-proj4-camera
``

Use browserify with glslify to use this
module.

license

BSD