I'm not able to get my changes to material.custom.value to change the behavior of the shader. I'm able to set an initial value, and the shader uses that, but any changes are ignored. I reassigned the CustomMaterial to the ModelComponent as you suggested, and even reassigned the ModelComponent to the ModelEntity, but no effect. The callback changing the value is definitely getting called and setting the value. Help!
My Swift code:
import SwiftUI
import RealityKit
import Combine
// A class with a per-frame callback to change a custom uniform for the geometry shader
class TestData {
var entity: ModelEntity? = nil
var model: ModelComponent? = nil
var material: CustomMaterial? = nil
var theta = Float(0)
func SetupCallback( _ arView: ARView) {
_ = arView.scene.subscribe(to: SceneEvents.Update.self) { _ in
// *** This value does get changed, but it's not reflected in the geometry shader
self.material!.custom.value = simd_float4( 0.5 * sin( self.theta ), 0, 0, 0 )
self.model?.materials = [self.material!]
self.entity?.model = self.model!
// print("x offset = ", self.material!.custom.value[0])
self.theta += 0.05
}
}
}
struct ContentView : View {
var body: some View {
return ARViewContainer().edgesIgnoringSafeArea(.all)
}
}
struct ARViewContainer: UIViewRepresentable {
let testData = TestData()
func makeUIView(context: Context) -> ARView {
let arView = ARView(frame: .zero)
// Create a simple box
let box = MeshResource.generateBox(size: 0.3)
// Create a custom materal with a Geometry shader -
let mtlLibrary = MTLCreateSystemDefaultDevice()!.makeDefaultLibrary()!
let geometryShader = CustomMaterial.GeometryModifier(
named: "moveVertices", in: mtlLibrary
)
testData.material = try! CustomMaterial(
from: SimpleMaterial(color: .orange, isMetallic: false),
geometryModifier: geometryShader )
// *** This initial value does make it to the Geometry shader
testData.material!.custom.value = simd_float4(0.5, 0, 0, 0)
// Create an entity with the box and custom material with geometry modifier
// let entity = ModelEntity(mesh: box, materials: [testData.material!])
testData.model = ModelComponent(mesh: box, materials: [testData.material!])
testData.entity = ModelEntity()
testData.entity!.model = testData.model!
// Create an anchor in front of us and add the box to it
let originAnchor = AnchorEntity(world: simd_float3( 0, -1, -1 ))
originAnchor.addChild(testData.entity!)
arView.scene.anchors.append(originAnchor)
// Set up the per-frame callback subscription
testData.SetupCallback( arView )
return arView
}
func updateUIView(_ uiView: ARView, context: Context) {}
}
#if DEBUG
struct ContentView_Previews : PreviewProvider {
static var previews: some View {
ContentView()
}
}
#endif
and my GeometryModifier:
#include <metal_stdlib>
#include <RealityKit/RealityKit.h>
using namespace metal;
[[visible]]
void moveVertices(realitykit::geometry_parameters params)
{
// Interpret custom_parameter as a position offset
float4 posOffset = float4( params.uniforms().custom_parameter());
params.geometry().set_model_position_offset(float3(posOffset));
}
