Cesium Ground-Push Plugin

A plugin that enables "excavating" terrain of a defined rectangle within Cesium. It allows a user to define an rectangle and push the terrain within that region up or down. The pushed region can also be textured with a different terrain tile. This could potentially be used to visualise geospatial data or imagery in subsurface context. Checkout the demo.

Cesium version

Currently working with Cesium versions 1.0 through to 1.2. For earlier releases, please check the Ground-Push Plugin releases.

License

Apache 2.0. Free for commercial and non-commercial use. See LICENSE.md.

Usage

Include the following into your source:

<script type="text/javascript" src="[your path to Cesium]/Cesium.js"></script>
<script type="text/javascript" src="GroundPushGlobeSurfaceShaderSet.js"></script>
<script type="text/javascript" src="GroundPushGlobeVS.js"></script>
<script type="text/javascript" src="GroundPushGlobeFS.js"></script>
<script type="text/javascript" src="GroundPush.js"></script>

Before you do anything with Cesium you must setup and initialise the Ground-Push plugin.

First, setup the options you require for the ground-push. Currently these include:

• pushDepth - The initial height of the push region in metres.
• pushRectangle - Required: A Cesium Rectangle of the region to be pushed.
• pushBaseTint - A Cesium Cartesian3 representing the RGB colour tint of the base of the pushed region.
• pushSidesTint - A Cesium Cartesian3 representing the RGB colour tint of the sides of the pushed region.

E.g.

var options = {
	pushRectangle : new Cesium.Rectangle( 0.0, 0.0, 0.1, 0.1 ),	// in radians
	pushDepth : -10000,										// in metres
	pushSidesTint : new Cesium.Cartesian3( 0.7, 0.6, 0.5 )	// rgb
};

Then initialise ground-push by passing in Cesium and options:

var gp = new GroundPush(Cesium, options);

If you want to apply a different texture to the pushed region you can use a Cesium Imagery Layer. Create it and add it as usual, then define the showOnlyInPushedRegion to true on that layer:

var imageryLayers = globe.imageryLayers;
var imageryProvider = new Cesium.TileMapServiceImageryProvider({
	url : 'http://cesium.agi.com/blackmarble',
	maximumLevel : 8,
	credit : 'Black Marble imagery courtesy NASA Earth Observatory',

    // Limit the rectangle of the imagery layer so that tiles
    // that will never be visible aren't loaded.
    rectangle : gp.getOuterRectangle()
});
imageryLayers.addImageryProvider(imageryProvider);

// Define this property to limit the ImageryLayer to the push region.
imageryLayers.get(1).showOnlyInPushedRegion = true;

You can change the push depth at any time simply by accessing the pushDepth property of the GroundPush object:

gp.pushDepth = -20000;

Currently, however, you cannot change the push rectangle once ground-push has been initialised.

Contributing

Your more than welcome to contribute. Please do this via a pull request.

Known Issues

• Zooming too close to the pushed region - tiles within the push rectangle will disappear due to culling.
• Horizon culling can be an issue at low angles.
• Changing the push rectangle region once initialised does not work correctly.