Table of Contents for
Mastering OpenLayers 3

Version ebook / Retour

Cover image for bash Cookbook, 2nd Edition Mastering OpenLayers 3 by Gábor Farkas Published by Packt Publishing, 2016
  1. Cover
  2. Table of Contents
  3. Mastering OpenLayers 3
  4. Mastering OpenLayers 3
  5. Credits
  6. About the Author
  7. About the Reviewer
  8. www.PacktPub.com
  9. Preface
  10. What you need for this book
  11. Who this book is for
  12. Conventions
  13. Reader feedback
  14. Customer support
  15. 1. Creating Simple Maps with OpenLayers 3
  16. Structure of OpenLayers 3
  17. Building the layout
  18. Using the API documentation
  19. Debugging the code
  20. Summary
  21. 2. Applying Custom Styles
  22. Customizing the default appearance
  23. Styling vector layers
  24. Customizing the appearance with JavaScript
  25. Creating a WebGIS client layout
  26. Summary
  27. 3. Working with Layers
  28. Building a layer tree
  29. Adding layers dynamically
  30. Adding vector layers with the File API
  31. Adding vector layers with a library
  32. Removing layers dynamically
  33. Changing layer attributes
  34. Changing the layer order with the Drag and Drop API
  35. Clearing the message bar
  36. Summary
  37. 4. Using Vector Data
  38. Accessing attributes
  39. Setting attributes
  40. Validating attributes
  41. Creating thematic layers
  42. Saving vector data
  43. Saving with WFS-T
  44. Modifying the geometry
  45. Summary
  46. 5. Creating Responsive Applications with Interactions and Controls
  47. Building the toolbar
  48. Mapping interactions to controls
  49. Building a set of feature selection controls
  50. Adding new vector layers
  51. Building a set of drawing tools
  52. Modifying and snapping to features
  53. Creating new interactions
  54. Building a measuring control
  55. Summary
  56. 6. Controlling the Map – View and Projection
  57. Customizing a view
  58. Constraining a view
  59. Creating a navigation history
  60. Working with extents
  61. Rotating a view
  62. Changing the map's projection
  63. Creating custom animations
  64. Summary
  65. 7. Mastering Renderers
  66. Using different renderers
  67. Creating a WebGL map
  68. Drawing lines and polygons with WebGL
  69. Blending layers
  70. Clipping layers
  71. Exporting a map
  72. Creating a raster calculator
  73. Creating a convolution matrix
  74. Clipping a layer with WebGL
  75. Summary
  76. 8. OpenLayers 3 for Mobile
  77. Responsive styling with CSS
  78. Generating geocaches
  79. Adding device-dependent controls
  80. Vectorizing the mobile version
  81. Making the mobile application interactive
  82. Summary
  83. 9. Tools of the Trade – Integrating Third-Party Applications
  84. Exporting a QGIS project
  85. Importing shapefiles
  86. Spatial analysis with Turf
  87. Spatial analysis with JSTS
  88. 3D rendering with Cesium
  89. Summary
  90. 10. Compiling Custom Builds with Closure
  91. Configuring Node JS
  92. Compiling OpenLayers 3
  93. Bundling an application with OpenLayers 3
  94. Extending OpenLayers 3
  95. Creating rich documentation with JSDoc
  96. Summary
  97. Index

Creating a WebGL map

In the first example, called ch07_webgl, we will create our first WebGL map. We bring our application to its limits, displaying more than 200,000 points on a single map. If you haven't performed this test already, you must be thinking that the magnitude of features will render our application totally unresponsive and useless. Let's make an attempt to perform this test, though. For this example, we only have to modify our map constructor using our new vector layer and the WebGL renderer:

var map = new ol.Map({
    target: 'map',
    layers: [
        […]
        new ol.layer.Vector({
            source: new ol.source.Vector({
                format: new ol.format.GeoJSON({
                    defaultDataProjection: 'EPSG:4326'
                }),
                url: '../../res/switzerland_points_osm.geojson',
                attributions: [
                    new ol.Attribution({
                        html: 'Switzerland Points © OpenStreetMap Contributors'
                    })
                ]
            }),
            name: 'Switzerland Points'
        })
    ],
    […]
   view: new ol.View({
        center: [910000, 5900000],
        zoom: 9
    }),
    renderer: 'webgl'
});

If you save the example and load it in a browser, you will be able to take a look at all the points that are rendered after some processing time. The map is quite hard to handle on lower scales; however, it is still manageable. When we zoom in and out on higher scales, the map becomes responsive again:

Creating a WebGL map

Tip

Be patient when you load the example. The library has to parse a lot of points; thus, it will need some time.

The only reason our application didn't freeze was due to the utilization of the GPU via the WebGL renderer. With proper hardware acceleration, we can display bigger datasets with acceptable performance.

There is only one serious limitation of this renderer: it cannot draw lines or polygons. The library will support such rendering methods over time; however, using vector lines and polygons are currently not supported. Furthermore, if we try to use line and polygon datasets with the WebGL renderer, the application will throw an error and stop running.