Inverted geometry for procedural buildings

[z3nth10n]

Description

For some reason, creating a building with the desired foundation points it creates inverted buildings:

Version

• Unity: 2019.4.11f
• ProceduralToolkit: Latest commit -- not sure (using package manager)

Steps to reproduce

Just download the project using the package manager, then copy the Samples folder into a folder of the project. Then I created this script:

    public class BuildingPlanner : MonoSingleton<BuildingPlanner>
    {
        public ProceduralFacadeConstructor proceduralFacadeConstructor;
        public ProceduralFacadePlanner proceduralFacadePlanner;
        public ProceduralRoofConstructor proceduralRoofConstructor;
        public ProceduralRoofPlanner proceduralRoofPlanner;

        // Start is called before the first frame update
        private void Start()
        {
        }

        // Update is called once per frame
        private void Update()
        {
        }
    }

Which is a script with a singleton pattern instance implemented with MonoBehaviour.

Then I call this function for generating a building:

        private static BuildingGenerator GenerateBuilding(int buildingIndex, BuildingGenerator.Config config, out Transform generatedBuild)
        {
            var builds = GameObject.Find("Builds");

            if (builds == null)
                builds = new GameObject("Builds");

            var build = new GameObject("Build");
            build.transform.parent = builds.transform;

            var building = City.Instance.buildings.ElementAt(buildingIndex);
            var generator = new BuildingGenerator();
            {
                generator.SetFacadeConstructor(BuildingPlanner.Instance.proceduralFacadeConstructor);
                generator.SetFacadePlanner(BuildingPlanner.Instance.proceduralFacadePlanner);
                generator.SetRoofConstructor(BuildingPlanner.Instance.proceduralRoofConstructor);
                generator.SetRoofPlanner(BuildingPlanner.Instance.proceduralRoofPlanner);

                generatedBuild = generator.Generate(building.Pol.Edges.Select(x => CityGenerator.SConv.ConvertVector(x)).ToList(), config,
                    build.transform);
            }

            build.transform.position = City.GetBuildingCenter(building);

            return generator;
        }

Which generates a building froma json file which contains a dictionary (index and List).

[BasmanovDaniil]

Hello! You need to reverse the order of vertices in your polygons and everything should work. The generator assumes that foundation polygons have clockwise direction.

generatedBuild = generator.Generate(building.Pol.Edges.Select(x => CityGenerator.SConv.ConvertVector(x)).Reverse().ToList(), config, build.transform);

You can check orientation with this code:

public static Orientation GetOrientation(List<Vector2> polygon)
{
    if (polygon.Count < 3) return Orientation.NonOrientable;
    float signedArea = GetSignedArea(polygon);
    if (signedArea > 0) return Orientation.Clockwise;
    if (signedArea < 0) return Orientation.CounterClockwise;
    return Orientation.NonOrientable;
}

public static float GetSignedArea(List<Vector2> polygon)
{
    if (polygon.Count < 3) return 0;
    float a = 0;
    for (int i = 0; i < polygon.Count; i++)
    {
        a += VectorE.PerpDot(polygon.GetLooped(i - 1), polygon[i]);
    }
    return a/2;
}

public enum Orientation
{
    CounterClockwise = -1,
    NonOrientable = 0,
    Clockwise = 1,
}

[BasmanovDaniil]

Sorry, there was an error in my code, signed area is negative for clockwise polygons. The correct code should be:

public static Orientation GetOrientation(List<Vector2> polygon)
{
    if (polygon.Count < 3) return Orientation.NonOrientable;
    float signedArea = GetSignedArea(polygon);
    if (signedArea > 0) return Orientation.CounterClockwise;
    if (signedArea < 0) return Orientation.Clockwise;
    return Orientation.NonOrientable;
}

[BasmanovDaniil]

Commited a bit more robust Geometry.GetOrientation and Geometry.GetSignedArea to the repository, you can use them as a reference too.

[z3nth10n]

Thanks, I updated the package, now this problem is gone.