GeometryGenerator.h

#pragma once

#include <DirectXMath.h>
#include <vector>

namespace BRE {
// To generate procedurally the geometry of 
// common mathematical objects.
//
// All triangles are generated "outward" facing.
namespace GeometryGenerator {
struct Vertex {
    Vertex() = default;
    explicit Vertex(const DirectX::XMFLOAT3& position,
                    const DirectX::XMFLOAT3& normal,
                    const DirectX::XMFLOAT3& tangent,
                    const DirectX::XMFLOAT2& uv);

    ~Vertex() = default;
    Vertex(const Vertex&) = default;
    Vertex(Vertex&&) = default;
    Vertex& operator=(Vertex&&) = default;

    DirectX::XMFLOAT3 mPosition = { 0.0f, 0.0f, 0.0f };
    DirectX::XMFLOAT3 mNormal = { 0.0f, 0.0f, 0.0f };
    DirectX::XMFLOAT3 mTangent = { 0.0f, 0.0f, 0.0f };
    DirectX::XMFLOAT2 mUV = { 0.0f, 0.0f };
};

struct MeshData {
    std::vector<Vertex> mVertices;
    std::vector<std::uint32_t> mIndices32;
    std::vector<std::uint16_t>& GetIndices16() noexcept;

private:
    std::vector<std::uint16_t> mIndices16{};
};

// Centered at the origin.
// Preconditions:
// - 
void CreateBox(const float width,
               const float height,
               const float depth,
               const std::uint32_t numSubdivisions,
               MeshData& meshData) noexcept;

// Centered at the origin.
void CreateSphere(const float radius,
                  const std::uint32_t sliceCount,
                  const std::uint32_t stackCount,
                  MeshData& meshData) noexcept;

// Centered at the origin.
void CreateGeosphere(const float radius,
                     const std::uint32_t numSubdivisions,
                     MeshData& meshData) noexcept;

// Creates a cylinder parallel to the y-axis, and centered about the origin.  
// The bottom and top radius can vary to form various cone shapes rather than true
// cylinders.  The slices and stacks parameters control the degree of tessellation.
void CreateCylinder(const float bottomRadius,
                    const float topRadius,
                    const float height,
                    const std::uint32_t sliceCount,
                    const std::uint32_t stackCount,
                    MeshData& meshData) noexcept;

// Creates an row x columns grid in the xz-plane with rows rows and columns columns, centered
// at the origin with the specified width and depth.
void CreateGrid(const float width,
                const float depth,
                const std::uint32_t rows,
                const std::uint32_t columns,
                MeshData& meshData) noexcept;
}
}