how to continuously animate an SCNProgram shader within an SCNScene / SCNView? - scenekit

Question

Within a MacOS app, I have a pattern defined by a SCNProgram that is mapped to an SCNPlane.
It looks like this:
The shader is supposed to make the rows of triangles shift , like in this video. The video is a screen grab of the same shader running inside of an MTKview.
animated texture
In the SceneKit version of this shader, the shader only animates when I click on the plane within the view.
How do I make the SceneKit view (or Scene?) continually animate the shader all the time? Again this app is on MacOS. I have tried setting
self.gameView!.isPlaying = true
but that doesn't seem to fix the problem
Here is the Metal shader:
#include <metal_stdlib>
using namespace metal;
#include <SceneKit/scn_metal>
struct myPlaneNodeBuffer {
float4x4 modelTransform;
float4x4 modelViewTransform;
float4x4 normalTransform;
float4x4 modelViewProjectionTransform;
float2x3 boundingBox;
};
typedef struct {
float3 position [[ attribute(SCNVertexSemanticPosition) ]];
float2 texCoords [[ attribute(SCNVertexSemanticTexcoord0) ]];
} VertexInput;
static float rand(float2 uv)
{
return fract(sin(dot(uv, float2(12.9898, 78.233))) * 43758.5453);
}
static float2 uv2tri(float2 uv)
{
float sx = uv.x - uv.y / 2;
float sxf = fract(sx);
float offs = step(fract(1 - uv.y), sxf);
return float2(floor(sx) * 2 + sxf + offs, uv.y);
}
struct SimpleVertexWithUV
{
float4 position [[position]];
float2 uv;
};
vertex SimpleVertexWithUV trianglequiltVertex(VertexInput in [[ stage_in ]],
constant SCNSceneBuffer& scn_frame [[buffer(0)]],
constant myPlaneNodeBuffer& scn_node [[buffer(1)]])
{
SimpleVertexWithUV vert;
vert.position = scn_node.modelViewProjectionTransform * float4(in.position, 1.0);
vert.uv = in.texCoords;
return vert;
}
fragment float4 trianglequiltFragment(SimpleVertexWithUV in [[stage_in]],
constant SCNSceneBuffer& scn_frame [[buffer(0)]],
constant myPlaneNodeBuffer& scn_node [[buffer(1)]])
{
float4 fragColor;
float2 uv = in.uv*10;
float timer = scn_frame.time;
uv.y += timer;
float t = timer * 0.8;
float tc = floor(t);
float tp = smoothstep(0, 0.8, fract(t));
float2 r1 = float2(floor(uv.y), tc);
float2 r2 = float2(floor(uv.y), tc + 1);
float offs = mix(rand(r1), rand(r2), tp);
uv.x += offs * 8;
float2 p = uv2tri(uv);
float ph = rand(floor(p)) * 6.3 + p.y * 0.2;
float c = abs(sin(ph + timer));
fragColor = float4(c, c, c, 1);
return(fragColor);
}
here is the view controller:
import SceneKit
import QuartzCore
class GameViewController: NSViewController {
#IBOutlet weak var gameView: GameView!
override func awakeFromNib(){
super.awakeFromNib()
// create a new scene
let scene = SCNScene()
Swift.print(gameView.colorPixelFormat.rawValue)
// create and add a camera to the scene
let cameraNode = SCNNode()
cameraNode.camera = SCNCamera()
scene.rootNode.addChildNode(cameraNode)
// place the camera
cameraNode.position = SCNVector3(x: 0, y: 0, z: 15)
// turn off default lighting
self.gameView!.autoenablesDefaultLighting = false
// set the scene to the view
self.gameView!.scene = scene
// allows the user to manipulate the camera
self.gameView!.allowsCameraControl = true
// show statistics such as fps and timing information
self.gameView!.showsStatistics = true
// configure the view
self.gameView!.backgroundColor = NSColor.black
// play it always?
self.gameView!.isPlaying = true
var geometry:SCNGeometry
geometry = SCNPlane(width:10, height:10)
let geometryNode = SCNNode(geometry: geometry)
let program = SCNProgram()
program.fragmentFunctionName = "trianglequiltFragment"
program.vertexFunctionName = "trianglequiltVertex"
let gradientMaterial = SCNMaterial()
gradientMaterial.program = program
gradientMaterial.specular.contents = NSColor.black
gradientMaterial.locksAmbientWithDiffuse = true
geometry.materials = [gradientMaterial]
geometryNode.geometry?.firstMaterial?.lightingModel = .constant
scene.rootNode.addChildNode(geometryNode)
}
}

Answer 1

Try setting:
gameView?.rendersContinuously = true
(You don’t need all those extra ‘self.’s either.)