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Point Cloud in SceneKit


#1

Hello, I have a simple problem. I have a sorted array of a million 2D points. I would like to use SceneKit Point Cloud Rendering to display the points that leverages GPU cycles for a great user experience. Can i get some help on how this can be done? I have a sample program I have below for rendering a small array of points and also a sample sphere but none of the points actually render. Only the sphere renders. I worked with Apple support to resolve this to no avail. Any help is greatly appreciated!

#import “ViewController.h”

typedef struct {

float x, y, z; // position

float r, g, b; // color

} MyVertex;

typedef struct {

float x, y, z; // position

} MyPoint;

  • (void)viewDidLoad {

    [super viewDidLoad];

    // Do any additional setup after loading the view, typically from a nib.

// SCNScene *scene = [SCNScene sceneNamed:@“scene.scnassets/scene.scn”];

SCNScene *scene = [SCNScene scene];

if(scene == nil) {

    return;

}



SCNNode *cameraNode = [SCNNode node];

cameraNode.camera = [SCNCamera camera];

cameraNode.position = SCNVector3Make(0, 0, 10);

[scene.rootNode addChildNode:cameraNode];



SCNNode *lightNode = [SCNNode node];

lightNode.light = [SCNLight light];

lightNode.light.type = SCNLightTypeOmni;

lightNode.position = SCNVector3Make(0, 3, 3);

[scene.rootNode addChildNode:lightNode];


// test sphere

SCNNode *sphere = [SCNNode node];

sphere.geometry = [SCNSphere sphereWithRadius:0.3];

sphere.position = SCNVector3Make(1, -2, -10);

[scene.rootNode addChildNode:sphere];



// test point cloud

// vertex data

MyVertex vertices[5] = {

    {-0.0378297, 0.12794, 0, 1.0, 0.0, 0.0},

    {-0.0447794, 0.128887, 0, 1.0, 0.0, 0.0},

    {-0.0680095, 0.151244, 0, 1.0, 0.0, 0.0},

    {-0.00228741, 0.13015, 0, 1.0, 0.0, 0.0},

    {-0.0226054, 0.126675, 0, 1.0, 0.0, 0.0}

};

MyPoint points[5] = {

    {-0.0378297, 0.12794, 0},

    {-0.0447794, 0.128887, 0},

    {-0.0680095, 0.151244, 0},

    {-0.00228741, 0.13015, 0},

    {-0.0226054, 0.126675, 0}

};


NSData *vertexData = [NSData dataWithBytes:vertices length:sizeof(vertices)];

NSData *pointData = [NSData dataWithBytes:points length:sizeof(points)];


// SCNGeometrySource objects for vertex and color

SCNGeometrySource *vertexSource, *colorSource;

vertexSource = [SCNGeometrySource geometrySourceWithData:vertexData semantic:SCNGeometrySourceSemanticVertex vectorCount:5 floatComponents:YES componentsPerVector:3 bytesPerComponent:sizeof(float) dataOffset:offsetof(MyVertex, x) dataStride:sizeof(MyVertex)];

colorSource = [SCNGeometrySource geometrySourceWithData:vertexData semantic:SCNGeometrySourceSemanticColor vectorCount:5 floatComponents:YES componentsPerVector:3 bytesPerComponent:sizeof(float) dataOffset:offsetof(MyVertex, r) dataStride:sizeof(MyVertex)];



// SCNGeometryElement

SCNGeometryElement *element = [SCNGeometryElement geometryElementWithData:pointData primitiveType:SCNGeometryPrimitiveTypePoint primitiveCount:5 bytesPerIndex:sizeof(float)];

element.pointSize = 1;

element.maximumPointScreenSpaceRadius = 3;

element.minimumPointScreenSpaceRadius = 1;



NSMutableArray<SCNGeometrySource *> *sources;

[sources addObject:vertexSource];

[sources addObject:colorSource];

NSMutableArray<SCNGeometryElement *> *elements;

[elements addObject:element];



SCNGeometry *geometry = [SCNGeometry geometryWithSources:sources elements:elements];

SCNNode *pcNode = [SCNNode nodeWithGeometry:geometry];

pcNode.position = SCNVector3Make(1, 2, 0);

[scene.rootNode addChildNode:pcNode];


sceneView.allowsCameraControl = TRUE;

sceneView.scene = scene;

}

  • (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];

    // Dispose of any resources that can be recreated.

}


#2

Also I would like the forum to consider Point Cloud Rendering as a tutorial topic if possible.


#3

@beepbeep Thank you for your suggestion - much appreciated! I will forward it to the tutorial team. Thanks again!


#4

@chrislanguage Can you please help with this when you get a chance? Thank you - much appreciated! :]