Scene properties expressions

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Update the orientation of a graphic using expressions based on its attributes.

Scene properties expressions sample

Use case

Instead of reading the attribute and changing the rotation on the symbol for a single graphic (a manual CPU operation), you can bind the rotation to an expression that applies to the whole overlay (an automatic GPU operation). This usually results in a noticeable performance boost (smooth rotations).

How to use the sample

Adjust the heading and pitch sliders to rotate the cone.

How it works

  1. Create an AGSGraphicsOverlay.
  2. Create an AGSSimpleRenderer and set its sceneProperties.
  3. Set headingExpression to [HEADING] and pitchExpression to [PITCH].
  4. Apply the renderer to the graphics overlay.
  5. Create an AGSGraphic and add it to the overlay.
  6. To update the graphic's rotation, update the HEADING or PITCH property in the graphic's attributes.

Relevant API

  • AGSGraphicsOverlay
  • AGSSceneProperties
  • AGSSimpleRenderer

Tags

3D, expression, graphics, heading, pitch, rotation, scene, symbology

Sample Code

ScenePropertiesExpressionsViewController.swift
                                                                            
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//
// Copyright 2016 Esri.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import UIKit
import ArcGIS

class ScenePropertiesExpressionsViewController: UIViewController {
    @IBOutlet var sceneView: AGSSceneView!
    @IBOutlet var headingLabel: UILabel!
    @IBOutlet var pitchLabel: UILabel!

    private var coneGraphic: AGSGraphic!

    override func viewDidLoad() {
        super.viewDidLoad()

        // add the source code button item to the right of navigation bar
        (self.navigationItem.rightBarButtonItem as! SourceCodeBarButtonItem).filenames = ["ScenePropertiesExpressionsViewController"]

        // initialize scene with streets basemap
        let scene = AGSScene(basemap: .streets())
        // assign scene to the scene view
        self.sceneView.scene = scene

        // set the viewpoint camera
        let point = AGSPoint(x: 83.9, y: 28.4, z: 5200, spatialReference: .wgs84())
        let camera = AGSCamera(lookAt: point, distance: 1000, heading: 0, pitch: 50, roll: 0)
        self.sceneView.setViewpointCamera(camera)

        // create a graphics overlay
        let graphicsOverlay = AGSGraphicsOverlay()
        graphicsOverlay.sceneProperties?.surfacePlacement = .relative

        // add it to the scene view
        self.sceneView.graphicsOverlays.add(graphicsOverlay)

        // add renderer using rotation expressions
        let renderer = AGSSimpleRenderer()
        renderer.sceneProperties?.headingExpression = "[HEADING]"
        renderer.sceneProperties?.pitchExpression = "[PITCH]"
        graphicsOverlay.renderer = renderer

        // create a red cone graphic
        let coneSymbol = AGSSimpleMarkerSceneSymbol(style: .cone, color: .red, height: 200, width: 100, depth: 100, anchorPosition: .center)
        coneSymbol.pitch = -90  // correct symbol's default pitch
        let conePoint = AGSPoint(x: 83.9, y: 28.404, z: 5000, spatialReference: .wgs84())
        let coneAttributes = ["HEADING": 0, "PITCH": 0]
        let coneGraphic = AGSGraphic(geometry: conePoint, symbol: coneSymbol, attributes: coneAttributes)
        graphicsOverlay.graphics.add(coneGraphic)
        self.coneGraphic = coneGraphic
    }

    @IBAction func headingSliderValueChanged(_ slider: UISlider) {
        coneGraphic.attributes["HEADING"] = slider.value
        // update label
        self.headingLabel.text = "\(Int(slider.value))"
    }

    @IBAction func pitchSliderValueChanged(_ slider: UISlider) {
        coneGraphic.attributes["PITCH"] = slider.value
        // update label
        self.pitchLabel.text = "\(Int(slider.value))"
    }
}

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