[Unreal Engine 5] 実行時に mesh の頂点座標を変化させる

結論

MyDynamicMeshActor.cpp

#include "MyDynamicMeshActor.h"
#include "DynamicMesh/DynamicMesh3.h"
#include <numbers>
#include <cmath>

namespace {
    double PI2 = 2.0 * std::numbers::pi;
    const FVector3d vertex[] = { {0,0,0},{0,1,0},{1,0,0},{1,1,0.5} };
    const double scale = 200.0;
}

void AMyDynamicMeshActor::BeginPlay()
{
    Super::BeginPlay();
    auto meshCmp = GetDynamicMeshComponent();
    auto mesh = meshCmp->GetMesh();

    mesh->AppendVertex(vertex[0] * scale);
    mesh->AppendVertex(vertex[1] * scale);
    mesh->AppendVertex(vertex[2] * scale);
    mesh->AppendVertex(vertex[3] * scale);
    mesh->AppendTriangle(0, 1, 2);
    mesh->AppendTriangle(3, 2, 1);

    meshCmp->NotifyMeshUpdated();

    meshCmp->EnableComplexAsSimpleCollision();
    meshCmp->UpdateCollision();
}

void AMyDynamicMeshActor::Tick(float DeltaSeconds)
{
    Super::Tick(DeltaSeconds);
    auto meshCmp = GetDynamicMeshComponent();
    auto mesh = meshCmp->GetMesh();

    double w = 0.5;
    phase += (w * DeltaSeconds);
    if (phase >= PI2) {
        phase -= PI2;
    }
    auto h1 = (std::sin(phase) + 1.0) * 0.3;
    auto h2 = (std::cos(phase) + 1.0) * 0.3;

    const FVector3d v1 = { scale, scale, h1*scale };
    const FVector3d v2 = { scale, 0, h2*scale };

    UE::Geometry::FIndex3i idx = {3,2,1};

    mesh->SetVertex(3, v1);
    mesh->SetVertex(2, v2);

    meshCmp->NotifyMeshUpdated();
    meshCmp->UpdateCollision(false);
}

補足

• BeginPlay() で Super::BeginPlay() を呼ばないと Tick() が呼ばれない
• Tick() 内の UpdateCollision() は引数 false が必要

参考にしたページ

• https://usagi.hatenablog.jp/entry/2017/07/05/164236