Surface shader can't get opacity from the texture

Question

Created Jul ’23

Replies 3

Boosts 0

Participants 2

I have a simple material with a texture that has transparency baked in (PNG file), this is the code that I did to load it :

 var triMat = SimpleMaterial(color: .orange, isMetallic: false)
 triMat.color = SimpleMaterial.BaseColor( tint: .white.withAlphaComponent(0.9), texture: MaterialParameters.Texture(try! .load(named: "whity_4x4")))
 self.components[ModelComponent.self] = try! ModelComponent(mesh: .generate(from: [meshDesc]), materials: [triMat])

It's pretty straight foward and it works fine, the geometry is a plane and it shows the texture correctly with transparency.

But when I try to create a surface shader (I want to animate the uv so it looks like it scrolls) the transparency become a black color. This is the part where I sample the texture for color and opacity

 auto color = params.textures().base_color().sample(textureSampler, float2(u1,v1));
 auto opacity = params.textures().opacity().sample(textureSampler, float2(u1,v1)).r;

and I set the surface color and opacity

params.surface().set_base_color(color.rgb);
params.surface().set_opacity(opacity);

upon debugging, it seems the opacity value is wrong (always 1) that's why it doesn't show as transparent. Did I do something wrong with sampling the texture opacity? I looked at the Metal API documentation that's how you supposed to do it?

Thanks for any help

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Answer 1

Graphics and Games Engineer OP

Apple

Jul ’23

Hi, can you share the Swift code that is creating your CustomMaterial and adding the texture?

0

Answer 2

yanuart OP

Jul ’23

Sure, here's the complete code Sure

       var triMat = SimpleMaterial(color: .orange, isMetallic: false)
       triMat.color = SimpleMaterial.BaseColor( tint: .white.withAlphaComponent(0.9), texture: MaterialParameters.Texture(try! .load(named: "whity_4x4")))
        self.components[ModelComponent.self] = try! ModelComponent(mesh: .generate(from: [meshDesc]), materials: [triMat])

        guard let device = MTLCreateSystemDefaultDevice() else {
            fatalError("Error creating default metal device.")
        }
        
        let library = device.makeDefaultLibrary()!

        let geomShader = CustomMaterial.GeometryModifier(named: "billboard", in: library)
        let surfaceShader = CustomMaterial.SurfaceShader(named: "scroll", in: library)
        
        var customMaterials:[RealityKit.Material] = []
        let materials = self.model?.materials
        
        for material in materials! {
            var material = try? CustomMaterial(from: material,
                                                   surfaceShader: surfaceShader,
                                                   geometryModifier: geomShader)
            //these custom values are to define the speed and direction of the scrolling
            material?.custom.value[0] = 100
            material?.custom.value[1] = 4
            material?.custom.value[2] = 4
            
            customMaterials.append(material!)
            
        }
        self.model?.materials = customMaterials

Hmm, are you saying that for opacity there should be another texture like normal texture? and we can't get the alpha value from the RGBA texture?

0

Answer 3

Graphics and Games Engineer OP

Apple

Jul ’23

You might need to set the blendingMode on the CustomMaterial to transparent.

https://developer.apple.com/documentation/realitykit/custommaterial/blending-swift.enum/transparent(opacity:)

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