Is there any _`android.graphics.Camera`_ equivalent (for 3D operations) so we can perform code like ...

# compose-desktop

[Guilherme Delgado]

Is there any android.graphics.Camera equivalent (for 3D operations) so we can perform code like this:

val matrix = android.graphics.Matrix() //we have androidx.compose.ui.graphics.Matrix
val camera = Camera()
    
drawScope.drawIntoCanvas { canvas ->
        //camera transformations like camera.rotateZ, etc..
        camera.getMatrix(matrix)
        matrix.preTranslate(-x, -y)
        matrix.postTranslate(x, y)

        canvas.save()
        canvas.nativeCanvas.concat(matrix)
        drawScope.draw...
        canvas.restore()
}

Thanks.

[Michael Paus]

Can’t you directly use the transform operations provided by the draw scope or the canvas? Why do you need a camera for that?

[Guilherme Delgado]

Because in Android we use the Camera for 3D (x,y,z) operations, with drawScope/Canvas I only have 2D (x,y)

[Michael Paus]

But in your example code above you are not using any 3D transforms. According to my understanding the Camera class is just a helper class to extract the 2D part from a 3D transform. I haven’t tried it but I assume that the Camera class source code could be easily adapted to Compose.

[Guilherme Delgado]

I didn’t put a complete example only: //camera transformations like camera.rotateZ, etc..

[Guilherme Delgado]

On Android that’s how I’ve created this, but I’m struggling to find similar in Compose Desktop.

[Michael Paus]

As I said, the Camera class does not seem to be readily available in Compose desktop but you might want to have a look at the original Android code.
Edit: The Android Camera class seems to be backed by some native code and thus cannot be adapted.

[Michael Paus]

On a closer look I think much of what you can do with the Camera in Android can already be done with the Compose Matrix class directly. https://developer.android.com/reference/kotlin/androidx/compose/ui/graphics/Matrix

[Guilherme Delgado]

Thanks, gonna have a look 👍

[Guilherme Delgado]

example:

val matrix = Matrix()
matrix.rotateX(45f)
matrix.rotateY(45f)
matrix.rotateZ(45f)
drawContext.canvas.save()
drawContext.canvas.concat(matrix)

draw...

drawContext.canvas.restore()

Seems to work 🙂

[Michael Paus]

Nice, and that code will work on Android AND Desktop,.

[Michael Paus]

This code could be further improved by using something like this:

drawScope.withTransform({transform(matrix)}) {
    ...
}

This should avoid all these concat/save/restore