The grey hue over the 3D model

Hello,

I've been trying to render these models in a VisionOS app using RealityKit's Model3D API. The heart seem to appear dark all the time. Any thoughts on why this would happen?

        Color.clear
            .overlay {
                Model3D(named: modelName, bundle: realityKitContentBundle) { model in
                    model.resizable()
                        .scaledToFit()
                        .rotation3DEffect(
                            Rotation3D(
                                eulerAngles: .init(angles: orientation, order: .xyz)
                            )
                        )
                        .frame(depth: modelDepth)
                        .offset(z: -modelDepth / 2)
                        .accessibilitySortPriority(1)
                } placeholder: {
                    ProgressView()
                        .offset(z: -modelDepth * 0.75)
                }
            }
            .dragRotation(yawLimit: .degrees(120), pitchLimit: .degrees(20))
            .offset(z: modelDepth)