XCEngine/editor/src/Viewport/SceneViewportMoveGizmo.cpp

#include "SceneViewportMoveGizmo.h"

#include "Core/IUndoManager.h"
#include "SceneViewportMath.h"
#include "SceneViewportPicker.h"

#include <XCEngine/Components/GameObject.h>
#include <XCEngine/Components/MeshFilterComponent.h>
#include <XCEngine/Components/MeshRendererComponent.h>
#include <XCEngine/Core/Math/Bounds.h>

namespace XCEngine {
namespace Editor {

namespace {

constexpr float kMoveGizmoHandleLengthPixels = 72.0f;
constexpr float kMoveGizmoHoverThresholdPixels = 10.0f;

Math::Vector3 GetAxisVector(SceneViewportGizmoAxis axis) {
    switch (axis) {
    case SceneViewportGizmoAxis::X:
        return Math::Vector3::Right();
    case SceneViewportGizmoAxis::Y:
        return Math::Vector3::Up();
    case SceneViewportGizmoAxis::Z:
        return Math::Vector3::Forward();
    case SceneViewportGizmoAxis::None:
    default:
        return Math::Vector3::Zero();
    }
}

Math::Color GetAxisBaseColor(SceneViewportGizmoAxis axis) {
    switch (axis) {
    case SceneViewportGizmoAxis::X:
        return Math::Color(0.91f, 0.09f, 0.05f, 1.0f);
    case SceneViewportGizmoAxis::Y:
        return Math::Color(0.45f, 1.0f, 0.12f, 1.0f);
    case SceneViewportGizmoAxis::Z:
        return Math::Color(0.11f, 0.29f, 1.0f, 1.0f);
    case SceneViewportGizmoAxis::None:
    default:
        return Math::Color::White();
    }
}

Math::Vector3 NormalizeVector3(const Math::Vector3& value, const Math::Vector3& fallback) {
    return value.SqrMagnitude() <= Math::EPSILON ? fallback : value.Normalized();
}

bool IsMouseInsideViewport(const SceneViewportMoveGizmoContext& context) {
    return context.mousePosition.x >= 0.0f &&
           context.mousePosition.y >= 0.0f &&
           context.mousePosition.x <= context.viewportSize.x &&
           context.mousePosition.y <= context.viewportSize.y;
}

void EncapsulateTransformedBounds(
    const Math::Bounds& localBounds,
    const Components::TransformComponent& transform,
    Math::Bounds& inOutBounds,
    bool& inOutHasBounds) {
    const Math::Vector3 localMin = localBounds.GetMin();
    const Math::Vector3 localMax = localBounds.GetMax();
    const Math::Vector3 corners[] = {
        Math::Vector3(localMin.x, localMin.y, localMin.z),
        Math::Vector3(localMax.x, localMin.y, localMin.z),
        Math::Vector3(localMin.x, localMax.y, localMin.z),
        Math::Vector3(localMin.x, localMin.y, localMax.z),
        Math::Vector3(localMax.x, localMax.y, localMin.z),
        Math::Vector3(localMin.x, localMax.y, localMax.z),
        Math::Vector3(localMax.x, localMin.y, localMax.z),
        Math::Vector3(localMax.x, localMax.y, localMax.z)
    };

    for (const Math::Vector3& localCorner : corners) {
        const Math::Vector3 worldCorner = transform.TransformPoint(localCorner);
        if (!inOutHasBounds) {
            inOutBounds = Math::Bounds(worldCorner, Math::Vector3::Zero());
            inOutHasBounds = true;
        } else {
            inOutBounds.Encapsulate(worldCorner);
        }
    }
}

void CollectRenderableWorldBoundsRecursive(
    const Components::GameObject& gameObject,
    Math::Bounds& inOutBounds,
    bool& inOutHasBounds) {
    if (!gameObject.IsActiveInHierarchy()) {
        return;
    }

    const auto* meshFilter = gameObject.GetComponent<Components::MeshFilterComponent>();
    const auto* meshRenderer = gameObject.GetComponent<Components::MeshRendererComponent>();
    if (meshFilter != nullptr &&
        meshRenderer != nullptr &&
        meshFilter->IsEnabled() &&
        meshRenderer->IsEnabled()) {
        const auto* mesh = meshFilter->GetMesh();
        if (mesh != nullptr) {
            EncapsulateTransformedBounds(mesh->GetBounds(), *gameObject.GetTransform(), inOutBounds, inOutHasBounds);
        }
    }

    for (size_t childIndex = 0; childIndex < gameObject.GetChildCount(); ++childIndex) {
        const Components::GameObject* child = gameObject.GetChild(childIndex);
        if (child != nullptr) {
            CollectRenderableWorldBoundsRecursive(*child, inOutBounds, inOutHasBounds);
        }
    }
}

float ComputeWorldUnitsPerPixel(
    const SceneViewportOverlayData& overlay,
    const Math::Vector3& worldPoint,
    float viewportHeight) {
    if (!overlay.valid || viewportHeight <= 1.0f) {
        return 0.0f;
    }

    const Math::Vector3 cameraForward = NormalizeVector3(overlay.cameraForward, Math::Vector3::Forward());
    const float depth = Math::Vector3::Dot(worldPoint - overlay.cameraPosition, cameraForward);
    if (depth <= Math::EPSILON) {
        return 0.0f;
    }

    return 2.0f * depth * std::tan(overlay.verticalFovDegrees * Math::DEG_TO_RAD * 0.5f) / viewportHeight;
}

Math::Vector3 GetGizmoWorldOrigin(const Components::GameObject& gameObject) {
    Math::Bounds worldBounds = {};
    bool hasBounds = false;
    CollectRenderableWorldBoundsRecursive(gameObject, worldBounds, hasBounds);
    return hasBounds ? worldBounds.center : gameObject.GetTransform()->GetPosition();
}

} // namespace

void SceneViewportMoveGizmo::Update(const SceneViewportMoveGizmoContext& context) {
    BuildDrawData(context);
    if (m_activeAxis == SceneViewportGizmoAxis::None && IsMouseInsideViewport(context)) {
        m_hoveredAxis = HitTestAxis(context.mousePosition);
    } else if (m_activeAxis == SceneViewportGizmoAxis::None) {
        m_hoveredAxis = SceneViewportGizmoAxis::None;
    } else {
        m_hoveredAxis = m_activeAxis;
    }

    RefreshHandleState();
}

bool SceneViewportMoveGizmo::TryBeginDrag(const SceneViewportMoveGizmoContext& context, IUndoManager& undoManager) {
    if (m_activeAxis != SceneViewportGizmoAxis::None ||
        m_hoveredAxis == SceneViewportGizmoAxis::None ||
        context.selectedObject == nullptr ||
        !m_drawData.visible ||
        undoManager.HasPendingInteractiveChange()) {
        return false;
    }

    Math::Ray worldRay;
    if (!BuildSceneViewportRay(
            context.overlay,
            context.viewportSize,
            context.mousePosition,
            worldRay)) {
        return false;
    }

    const Math::Vector3 worldAxis = GetAxisVector(m_hoveredAxis);
    Math::Vector3 dragPlaneNormal = Math::Vector3::Zero();
    if (!BuildSceneViewportAxisDragPlaneNormal(context.overlay, worldAxis, dragPlaneNormal)) {
        return false;
    }

    const Math::Vector3 objectWorldPosition = context.selectedObject->GetTransform()->GetPosition();
    const Math::Vector3 pivotWorldPosition = GetGizmoWorldOrigin(*context.selectedObject);
    const Math::Plane dragPlane = BuildSceneViewportPlaneFromPointNormal(pivotWorldPosition, dragPlaneNormal);
    float hitDistance = 0.0f;
    if (!worldRay.Intersects(dragPlane, hitDistance)) {
        return false;
    }

    undoManager.BeginInteractiveChange("Move Gizmo");
    if (!undoManager.HasPendingInteractiveChange()) {
        return false;
    }

    const Math::Vector3 hitPoint = worldRay.GetPoint(hitDistance);
    m_activeAxis = m_hoveredAxis;
    m_activeEntityId = context.selectedObject->GetID();
    m_activeAxisDirection = worldAxis;
    m_dragPlane = dragPlane;
    m_dragStartObjectWorldPosition = objectWorldPosition;
    m_dragStartPivotWorldPosition = pivotWorldPosition;
    m_dragStartAxisScalar = Math::Vector3::Dot(hitPoint - pivotWorldPosition, worldAxis);
    RefreshHandleState();
    return true;
}

void SceneViewportMoveGizmo::UpdateDrag(const SceneViewportMoveGizmoContext& context) {
    if (m_activeAxis == SceneViewportGizmoAxis::None ||
        context.selectedObject == nullptr ||
        context.selectedObject->GetID() != m_activeEntityId) {
        return;
    }

    Math::Ray worldRay;
    if (!BuildSceneViewportRay(
            context.overlay,
            context.viewportSize,
            context.mousePosition,
            worldRay)) {
        return;
    }

    float hitDistance = 0.0f;
    if (!worldRay.Intersects(m_dragPlane, hitDistance)) {
        return;
    }

    const Math::Vector3 hitPoint = worldRay.GetPoint(hitDistance);
    const float currentAxisScalar = Math::Vector3::Dot(hitPoint - m_dragStartPivotWorldPosition, m_activeAxisDirection);
    const float deltaScalar = currentAxisScalar - m_dragStartAxisScalar;
    context.selectedObject->GetTransform()->SetPosition(
        m_dragStartObjectWorldPosition + m_activeAxisDirection * deltaScalar);
}

void SceneViewportMoveGizmo::EndDrag(IUndoManager& undoManager) {
    if (m_activeAxis == SceneViewportGizmoAxis::None) {
        return;
    }

    if (undoManager.HasPendingInteractiveChange()) {
        undoManager.FinalizeInteractiveChange();
    }

    m_activeAxis = SceneViewportGizmoAxis::None;
    m_activeEntityId = 0;
    m_activeAxisDirection = Math::Vector3::Zero();
    m_dragStartObjectWorldPosition = Math::Vector3::Zero();
    m_dragStartPivotWorldPosition = Math::Vector3::Zero();
    m_dragStartAxisScalar = 0.0f;
    RefreshHandleState();
}

void SceneViewportMoveGizmo::CancelDrag(IUndoManager* undoManager) {
    if (undoManager != nullptr && undoManager->HasPendingInteractiveChange()) {
        undoManager->CancelInteractiveChange();
    }

    m_activeAxis = SceneViewportGizmoAxis::None;
    m_activeEntityId = 0;
    m_activeAxisDirection = Math::Vector3::Zero();
    m_dragStartObjectWorldPosition = Math::Vector3::Zero();
    m_dragStartPivotWorldPosition = Math::Vector3::Zero();
    m_dragStartAxisScalar = 0.0f;
    m_hoveredAxis = SceneViewportGizmoAxis::None;
    RefreshHandleState();
}

bool SceneViewportMoveGizmo::IsHoveringHandle() const {
    return m_hoveredAxis != SceneViewportGizmoAxis::None;
}

bool SceneViewportMoveGizmo::IsActive() const {
    return m_activeAxis != SceneViewportGizmoAxis::None;
}

uint64_t SceneViewportMoveGizmo::GetActiveEntityId() const {
    return m_activeEntityId;
}

const SceneViewportMoveGizmoDrawData& SceneViewportMoveGizmo::GetDrawData() const {
    return m_drawData;
}

void SceneViewportMoveGizmo::BuildDrawData(const SceneViewportMoveGizmoContext& context) {
    m_drawData = {};
    m_drawData.pivotRadius = 5.0f;

    const Components::GameObject* selectedObject = context.selectedObject;
    if (selectedObject == nullptr ||
        !context.overlay.valid ||
        context.viewportSize.x <= 1.0f ||
        context.viewportSize.y <= 1.0f) {
        return;
    }

    const Math::Vector3 gizmoWorldOrigin = GetGizmoWorldOrigin(*selectedObject);
    const SceneViewportProjectedPoint projectedPivot = ProjectSceneViewportWorldPoint(
        context.overlay,
        context.viewportSize.x,
        context.viewportSize.y,
        gizmoWorldOrigin);
    if (!projectedPivot.visible) {
        return;
    }

    m_drawData.visible = true;
    m_drawData.pivot = projectedPivot.screenPosition;
    const float worldUnitsPerPixel = ComputeWorldUnitsPerPixel(
        context.overlay,
        gizmoWorldOrigin,
        context.viewportSize.y);
    if (worldUnitsPerPixel <= Math::EPSILON) {
        m_drawData = {};
        return;
    }

    const float axisLengthWorld = worldUnitsPerPixel * kMoveGizmoHandleLengthPixels;

    const SceneViewportGizmoAxis axes[] = {
        SceneViewportGizmoAxis::X,
        SceneViewportGizmoAxis::Y,
        SceneViewportGizmoAxis::Z
    };
    for (size_t index = 0; index < m_drawData.handles.size(); ++index) {
        SceneViewportMoveGizmoHandleDrawData& handle = m_drawData.handles[index];
        handle.axis = axes[index];
        handle.start = projectedPivot.screenPosition;

        const Math::Vector3 axisEndWorld =
            gizmoWorldOrigin + GetAxisVector(handle.axis) * axisLengthWorld;
        const SceneViewportProjectedPoint projectedEnd = ProjectSceneViewportWorldPoint(
            context.overlay,
            context.viewportSize.x,
            context.viewportSize.y,
            axisEndWorld);
        if (projectedEnd.ndcDepth < 0.0f || projectedEnd.ndcDepth > 1.0f) {
            continue;
        }

        if ((projectedEnd.screenPosition - projectedPivot.screenPosition).SqrMagnitude() <= Math::EPSILON) {
            continue;
        }

        handle.end = projectedEnd.screenPosition;
        handle.visible = true;
        handle.color = GetAxisBaseColor(handle.axis);
    }
}

void SceneViewportMoveGizmo::RefreshHandleState() {
    for (SceneViewportMoveGizmoHandleDrawData& handle : m_drawData.handles) {
        if (!handle.visible) {
            continue;
        }

        handle.hovered = handle.axis == m_hoveredAxis;
        handle.active = handle.axis == m_activeAxis;
        handle.color = (handle.hovered || handle.active)
            ? Math::Color::Yellow()
            : GetAxisBaseColor(handle.axis);
    }
}

SceneViewportGizmoAxis SceneViewportMoveGizmo::HitTestAxis(const Math::Vector2& mousePosition) const {
    if (!m_drawData.visible) {
        return SceneViewportGizmoAxis::None;
    }

    const float hoverThresholdSq = kMoveGizmoHoverThresholdPixels * kMoveGizmoHoverThresholdPixels;
    SceneViewportGizmoAxis bestAxis = SceneViewportGizmoAxis::None;
    float bestDistanceSq = hoverThresholdSq;

    for (const SceneViewportMoveGizmoHandleDrawData& handle : m_drawData.handles) {
        if (!handle.visible) {
            continue;
        }

        const float distanceSq = DistanceToSegmentSquared(mousePosition, handle.start, handle.end);
        if (distanceSq > bestDistanceSq) {
            continue;
        }

        bestDistanceSq = distanceSq;
        bestAxis = handle.axis;
    }

    return bestAxis;
}

} // namespace Editor
} // namespace XCEngine