Which direction is positive z in the API?

[siliconlad]

I have the following script which creates, a circular sketch, 2 sketch points and 2 sketch lines (as below).

The code for this is shown below (based on the Construction Plane API sample)

import adsk.core, adsk.fusion, traceback

def run(context):
    ui = None
    try:
        app = adsk.core.Application.get()
        ui = app.userInterface

        # Create a document.
        doc = app.documents.add(adsk.core.DocumentTypes.FusionDesignDocumentType)

        product = app.activeProduct
        design = adsk.fusion.Design.cast(product)

        # Get the root component of the active design
        rootComp = design.rootComponent

        # Create sketch
        sketches = rootComp.sketches
        sketch = sketches.add(rootComp.xZConstructionPlane)

        # Create sketch circle
        sketchCircles = sketch.sketchCurves.sketchCircles
        centerPoint = adsk.core.Point3D.create(0, 0, 0)
        sketchCircles.addByCenterRadius(centerPoint, 5.0)

        # Create sketch line
        sketchLines = sketch.sketchCurves.sketchLines
        startPoint = adsk.core.Point3D.create(5, 5, 0)
        endPoint = adsk.core.Point3D.create(5, 10, 0)
        sketchLineOne = sketchLines.addByTwoPoints(startPoint, endPoint)
        endPointTwo = adsk.core.Point3D.create(10, 5, 0)
        sketchLineTwo = sketchLines.addByTwoPoints(startPoint, endPointTwo)

        # Create two sketch points
        sketchPoints = sketch.sketchPoints
        positionOne = adsk.core.Point3D.create(0, 5.0, 0)
        sketchPointOne = sketchPoints.add(positionOne)
        positionTwo = adsk.core.Point3D.create(5.0, 0, 0)
        sketchPointTwo = sketchPoints.add(positionTwo)

    except:
        if ui:
            ui.messageBox('Failed:\n{}'.format(traceback.format_exc()))

`startPoint` which is created with coordinates (5, 5, 0) is placed in position (5, 0, -5) according to my axis in the top right corner. Given that the sketch is on the xZConstructionPlane I would be able to understand how specifying (5, 5, 0) ends up as (5, 0, 5), but I cannot understand how (5, 5, 0) maps to (5, 0, -5)??

[john.kirchner · Accepted solution]

You can get information about the orientation of sketches in the API a few different ways. For example you can get the xDirection and yDirection from the sketch object. Here's a sketch created on the xZConstructionPlane

sketch.xDirection #(1.0, 0.0, 0.0)
sketch.yDirection #(0.0, 0.0, -1.0)

I've added the asArray() output next to each line. So the sketch positive X aligns to world/design positive X, sketch positive Y aligns to world/design negative Z.

This aligns with what is seen in the UI as well if you open up the sketch and look at the labelled axis

One last thing to note is that Fusion uses right handed coordinate systems.