BoxSphereGenerator.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
// Port of geometry3Sharp SphereGenerators
 
#pragma once
 
#include "MeshShapeGenerator.h"
#include "OrientedBoxTypes.h"
#include "Util/IndexUtil.h"
 
#include "GridBoxMeshGenerator.h"
 
namespace UE
{
namespace Geometry
{
 
 
class /*GEOMETRYCORE_API*/ FBoxSphereGenerator : public FGridBoxMeshGenerator
{
public:
 
    float Radius = 1;
 
    enum class ESphereProjectionMethod
    {
        NormalizedVector,
        CubeMapping             // produces more even distribution of quads
                                // see http://catlikecoding.com/unity/tutorials/cube-sphere/
                                // or http://mathproofs.blogspot.ca/2005/07/mapping-cube-to-sphere.html
    };
    ESphereProjectionMethod SphereProjectionMethod = ESphereProjectionMethod::CubeMapping;
 
    FMeshShapeGenerator& Generate() override
    {
        FGridBoxMeshGenerator::Generate();
 
        FVector3d Center = Box.Center();
        FVector3d AxX = Box.AxisX(), AxY = Box.AxisY(), AxZ = Box.AxisZ();
        for (int32 VertIdx = 0; VertIdx < Vertices.Num(); VertIdx++)
        {
            FVector3d V = Vertices[VertIdx] - Center;
            if (SphereProjectionMethod == ESphereProjectionMethod::CubeMapping) {
                double x = V.Dot(AxX) / Box.Extents.X;
                double y = V.Dot(AxY) / Box.Extents.Y;
                double z = V.Dot(AxZ) / Box.Extents.Z;
                double x2 = x * x, y2 = y * y, z2 = z * z;
                double sx = x * FMathd::Sqrt(1.0 - y2*0.5 - z2*0.5 + y2*z2/3.0);
                double sy = y * FMathd::Sqrt(1.0 - x2*0.5 - z2*0.5 + x2*z2/3.0);
                double sz = z * FMathd::Sqrt(1.0 - x2*0.5 - y2*0.5 + x2*y2/3.0);
                V = sx*AxX + sy*AxY + sz*AxZ;
            }
            Normalize(V);
            Vertices[VertIdx] = V;
        }
 
        for (int32 NormalIdx = 0; NormalIdx < Normals.Num(); NormalIdx++)
        {
            Normals[NormalIdx] = (FVector3f)Vertices[NormalParentVertex[NormalIdx]];
        }
 
        for (int32 VertIdx = 0; VertIdx < Vertices.Num(); VertIdx++)
        {
            Vertices[VertIdx] = Center + Radius*Vertices[VertIdx];
        }
 
        return *this;
    }
 
};
 
 
 
} // end namespace UE::Geometry
} // end namespace UE