Pulse effect in SceneKit - Objective C

GameViewController.h

//
//  GameViewController.h
//  pulseeffectobjectivec
//
//  Created by Lachlan Hurst on 10/3/17.
//  Copyright © 2017 Lachlan Hurst. All rights reserved.
//

#import <UIKit/UIKit.h>
#import <SceneKit/SceneKit.h>

@interface GameViewController : UIViewController

@end

GameViewController.m

//
//  GameViewController.m
//  pulseeffectobjectivec
//
//  Created by Lachlan Hurst on 10/3/17.
//  Copyright © 2017 Lachlan Hurst. All rights reserved.
//

#import "GameViewController.h"

@implementation GameViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    // create a new scene
    SCNScene *scene = [SCNScene scene];

    // create and add a camera to the scene
    SCNNode *cameraNode = [SCNNode node];
    cameraNode.camera = [SCNCamera camera];
    [scene.rootNode addChildNode:cameraNode];
    
    // place the camera
    cameraNode.position = SCNVector3Make(0, 0, 15);
    
    // create and add a light to the scene
    SCNNode *lightNode = [SCNNode node];
    lightNode.light = [SCNLight light];
    lightNode.light.type = SCNLightTypeOmni;
    lightNode.position = SCNVector3Make(0, 10, 10);
    [scene.rootNode addChildNode:lightNode];
    
    // create and add an ambient light to the scene
    SCNNode *ambientLightNode = [SCNNode node];
    ambientLightNode.light = [SCNLight light];
    ambientLightNode.light.type = SCNLightTypeAmbient;
    ambientLightNode.light.color = [UIColor darkGrayColor];
    [scene.rootNode addChildNode:ambientLightNode];
    
    SCNNode *boxNode = [SCNNode nodeWithGeometry:[SCNBox boxWithWidth:1.0 height:1.0 length:1.0 chamferRadius:0.0]];
    boxNode.geometry.firstMaterial.diffuse.contents = [UIColor redColor];
    [scene.rootNode addChildNode:boxNode];

    CGFloat pulseSize = 5.0;
    SCNPlane *pulsePlane = [SCNPlane planeWithWidth:pulseSize height:pulseSize];
    [pulsePlane.firstMaterial setDoubleSided:true];
    pulsePlane.firstMaterial.diffuse.contents = [UIColor blueColor];
    SCNNode *pulseNode = [SCNNode nodeWithGeometry:pulsePlane];

    NSString *pulseShaderModifier = [NSString stringWithFormat:
    @"#pragma transparent; \n"
    "vec4 originalColour = _surface.diffuse; \n"
    "vec4 transformed_position = u_inverseModelTransform * u_inverseViewTransform * vec4(_surface.position, 1.0); \n"
    "vec2 xy = vec2(transformed_position.x, transformed_position.y); \n"
    "float xyLength = length(xy); \n"
    "float xyLengthNormalised = xyLength/%f; \n"
    "float speedFactor = 1.5; \n"
    "float maxDist = fmod(u_time, speedFactor) / speedFactor; \n"
    "float distbasedalpha = step(maxDist, xyLengthNormalised); \n"
    "distbasedalpha = max(distbasedalpha, maxDist); \n"
    "_surface.diffuse = mix(originalColour, vec4(0.0), distbasedalpha);", pulseSize/2.0];

    NSDictionary *smdict = [NSDictionary dictionaryWithObject:pulseShaderModifier forKey:SCNShaderModifierEntryPointSurface];
    [pulsePlane.firstMaterial setShaderModifiers:smdict];

    [boxNode addChildNode:pulseNode];

    SCNLookAtConstraint *pulseNodeConstraint = [SCNLookAtConstraint lookAtConstraintWithTarget:cameraNode];
    NSArray *constraints = [NSArray arrayWithObject:pulseNodeConstraint];
    [pulseNode setConstraints:constraints];


    // animate the 3d object
    [boxNode runAction:[SCNAction repeatActionForever:[SCNAction rotateByX:0 y:2 z:0 duration:1]]];
    
    // retrieve the SCNView
    SCNView *scnView = (SCNView *)self.view;
    
    // set the scene to the view
    scnView.scene = scene;
    
    // allows the user to manipulate the camera
    scnView.allowsCameraControl = YES;
        
    // show statistics such as fps and timing information
    scnView.showsStatistics = YES;

    // configure the view
    scnView.backgroundColor = [UIColor lightGrayColor];
    
    // add a tap gesture recognizer
    UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleTap:)];
    NSMutableArray *gestureRecognizers = [NSMutableArray array];
    [gestureRecognizers addObject:tapGesture];
    [gestureRecognizers addObjectsFromArray:scnView.gestureRecognizers];
    scnView.gestureRecognizers = gestureRecognizers;
}

- (void) handleTap:(UIGestureRecognizer*)gestureRecognize
{
    // retrieve the SCNView
    SCNView *scnView = (SCNView *)self.view;
    
    // check what nodes are tapped
    CGPoint p = [gestureRecognize locationInView:scnView];
    NSArray *hitResults = [scnView hitTest:p options:nil];
    
    // check that we clicked on at least one object
    if([hitResults count] > 0){
        // retrieved the first clicked object
        SCNHitTestResult *result = [hitResults objectAtIndex:0];
        
        // get its material
        SCNMaterial *material = result.node.geometry.firstMaterial;
        
        // highlight it
        [SCNTransaction begin];
        [SCNTransaction setAnimationDuration:0.5];
        
        // on completion - unhighlight
        [SCNTransaction setCompletionBlock:^{
            [SCNTransaction begin];
            [SCNTransaction setAnimationDuration:0.5];
            
            material.emission.contents = [UIColor blackColor];
            
            [SCNTransaction commit];
        }];
        
        material.emission.contents = [UIColor redColor];
        
        [SCNTransaction commit];
    }
}

- (BOOL)shouldAutorotate
{
    return YES;
}

- (BOOL)prefersStatusBarHidden {
    return YES;
}

- (UIInterfaceOrientationMask)supportedInterfaceOrientations
{
    if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone) {
        return UIInterfaceOrientationMaskAllButUpsideDown;
    } else {
        return UIInterfaceOrientationMaskAll;
    }
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Release any cached data, images, etc that aren't in use.
}

@end