urho3d/bin/Data/Scripts/Editor/EditorGizmo.as

// Urho3D editor node transform gizmo handling

Node@ gizmoNode;
StaticModel@ gizmo;

const float axisMaxD = 0.1;
const float axisMaxT = 1.0;
const float rotSensitivity = 50.0;

EditMode lastGizmoMode;

// For undo
bool previousGizmoDrag;
bool needGizmoUndo;
Array<Transform> oldGizmoTransforms;

class GizmoAxis
{
    Ray axisRay;
    bool selected;
    bool lastSelected;
    float t;
    float d;
    float lastT;
    float lastD;

    GizmoAxis()
    {
        selected = false;
        lastSelected = false;
        t = 0.0;
        d = 0.0;
        lastT = 0.0;
        lastD = 0.0;
    }

    void Update(Ray cameraRay, float scale, bool drag)
    {
        // Do not select when UI has modal element
        if (ui.HasModalElement())
        {
            selected = false;
            return;
        }
        
        Vector3 closest = cameraRay.ClosestPoint(axisRay);
        Vector3 projected = axisRay.Project(closest);
        d = axisRay.Distance(closest);
        t = (projected - axisRay.origin).DotProduct(axisRay.direction);

        // Determine the sign of d from a plane that goes through the camera position to the axis
        Plane axisPlane(cameraNode.position, axisRay.origin, axisRay.origin + axisRay.direction);
        if (axisPlane.Distance(closest) < 0.0)
            d = -d;

        // Update selected status only when not dragging
        if (!drag)
        {
            selected = Abs(d) < axisMaxD * scale && t >= -axisMaxD * scale && t <= axisMaxT * scale;
            lastT = t;
            lastD = d;
        }
    }

    void Moved()
    {
        lastT = t;
        lastD = d;
    }
}

GizmoAxis gizmoAxisX;
GizmoAxis gizmoAxisY;
GizmoAxis gizmoAxisZ;

void CreateGizmo()
{
    gizmoNode = Node();
    gizmo = gizmoNode.CreateComponent("StaticModel");
    gizmo.model = cache.GetResource("Model", "Models/Editor/Axes.mdl");
    gizmo.materials[0] = cache.GetResource("Material", "Materials/Editor/RedUnlit.xml");
    gizmo.materials[1] = cache.GetResource("Material", "Materials/Editor/GreenUnlit.xml");
    gizmo.materials[2] = cache.GetResource("Material", "Materials/Editor/BlueUnlit.xml");
    gizmo.enabled = false;
    gizmo.viewMask = 0x80000000; // Editor raycasts use viewmask 0x7fffffff
    gizmo.occludee = false;
    gizmoNode.name = "EditorGizmo";

    gizmoAxisX.lastSelected = false;
    gizmoAxisY.lastSelected = false;
    gizmoAxisZ.lastSelected = false;
    lastGizmoMode = EDIT_MOVE;
}

void HideGizmo()
{
    if (gizmo !is null)
        gizmo.enabled = false;
}

void ShowGizmo()
{
    if (gizmo !is null)
    {
        gizmo.enabled = true;

        // Because setting enabled = false detaches the gizmo from octree,
        // and it is a manually added drawable, must readd to octree when showing
        if (editorScene.octree !is null)
            editorScene.octree.AddManualDrawable(gizmo);
    }
}

void UpdateGizmo()
{
    UseGizmo();
    PositionGizmo();
    ResizeGizmo();
}

void PositionGizmo()
{
    if (gizmo is null)
        return;

    Vector3 center(0, 0, 0);
    bool containsScene = false;

    for (uint i = 0; i < editNodes.length; ++i)
    {
        // Scene's transform should not be edited, so hide gizmo if it is included
        if (editNodes[i] is editorScene)
        {
            containsScene = true;
            break;
        }
        center += editNodes[i].worldPosition;
    }

    if (editNodes.empty || containsScene)
    {
        HideGizmo();
        return;
    }

    center /= editNodes.length;
    gizmoNode.position = center;

    if (axisMode == AXIS_WORLD || editNodes.length > 1)
        gizmoNode.rotation = Quaternion();
    else
        gizmoNode.rotation = editNodes[0].worldRotation;

    if (editMode != lastGizmoMode)
    {
        switch (editMode)
        {
        case EDIT_MOVE:
            gizmo.model = cache.GetResource("Model", "Models/Editor/Axes.mdl");
            break;

        case EDIT_ROTATE:
            gizmo.model = cache.GetResource("Model", "Models/Editor/RotateAxes.mdl");
            break;

        case EDIT_SCALE:
            gizmo.model = cache.GetResource("Model", "Models/Editor/ScaleAxes.mdl");
            break;
        }

        lastGizmoMode = editMode;
    }

    if ((editMode != EDIT_SELECT && !orbiting) && !gizmo.enabled)
        ShowGizmo();
    else if ((editMode == EDIT_SELECT || orbiting) && gizmo.enabled)
        HideGizmo();
}

void ResizeGizmo()
{
    if (gizmo is null || !gizmo.enabled)
        return;

    float scale = 0.1 / camera.zoom;

    if (camera.orthographic)
        scale *= camera.orthoSize;
    else
        scale *= (camera.view * gizmoNode.position).z;

    gizmoNode.scale = Vector3(scale, scale, scale);
}

void CalculateGizmoAxes()
{
    gizmoAxisX.axisRay = Ray(gizmoNode.position, gizmoNode.rotation * Vector3(1, 0, 0));
    gizmoAxisY.axisRay = Ray(gizmoNode.position, gizmoNode.rotation * Vector3(0, 1, 0));
    gizmoAxisZ.axisRay = Ray(gizmoNode.position, gizmoNode.rotation * Vector3(0, 0, 1));
}

void GizmoMoved()
{
    gizmoAxisX.Moved();
    gizmoAxisY.Moved();
    gizmoAxisZ.Moved();
}

void UseGizmo()
{
    if (gizmo is null || !gizmo.enabled || editMode == EDIT_SELECT)
    {
        StoreGizmoEditActions();
        previousGizmoDrag = false;
        return;
    }

    IntVector2 pos = ui.cursorPosition;
    if (ui.GetElementAt(pos) !is null)
        return;
    Ray cameraRay = GetActiveViewportCameraRay();
    float scale = gizmoNode.scale.x;

    // Recalculate axes only when not left-dragging
    bool drag = input.mouseButtonDown[MOUSEB_LEFT];
    if (!drag)
        CalculateGizmoAxes();

    gizmoAxisX.Update(cameraRay, scale, drag);
    gizmoAxisY.Update(cameraRay, scale, drag);
    gizmoAxisZ.Update(cameraRay, scale, drag);

    if (gizmoAxisX.selected != gizmoAxisX.lastSelected)
    {
        gizmo.materials[0] = cache.GetResource("Material", gizmoAxisX.selected ? "Materials/Editor/BrightRedUnlit.xml" :
            "Materials/Editor/RedUnlit.xml");
        gizmoAxisX.lastSelected = gizmoAxisX.selected;
    }
    if (gizmoAxisY.selected != gizmoAxisY.lastSelected)
    {
        gizmo.materials[1] = cache.GetResource("Material", gizmoAxisY.selected ? "Materials/Editor/BrightGreenUnlit.xml" :
            "Materials/Editor/GreenUnlit.xml");
        gizmoAxisY.lastSelected = gizmoAxisY.selected;
    }
    if (gizmoAxisZ.selected != gizmoAxisZ.lastSelected)
    {
        gizmo.materials[2] = cache.GetResource("Material", gizmoAxisZ.selected ? "Materials/Editor/BrightBlueUnlit.xml" :
            "Materials/Editor/BlueUnlit.xml");
        gizmoAxisZ.lastSelected = gizmoAxisZ.selected;
    };

    if (drag)
    {
        // Store initial transforms for undo when gizmo drag started
        if (!previousGizmoDrag)
        {
            oldGizmoTransforms.Resize(editNodes.length);
            for (uint i = 0; i < editNodes.length; ++i)
                oldGizmoTransforms[i].Define(editNodes[i]);
        }

        bool moved = false;

        if (editMode == EDIT_MOVE)
        {
            Vector3 adjust(0, 0, 0);
            if (gizmoAxisX.selected)
                adjust += Vector3(1, 0, 0) * (gizmoAxisX.t - gizmoAxisX.lastT);
            if (gizmoAxisY.selected)
                adjust += Vector3(0, 1, 0) * (gizmoAxisY.t - gizmoAxisY.lastT);
            if (gizmoAxisZ.selected)
                adjust += Vector3(0, 0, 1) * (gizmoAxisZ.t - gizmoAxisZ.lastT);

            moved = MoveNodes(adjust);
        }
        else if (editMode == EDIT_ROTATE)
        {
            Vector3 adjust(0, 0, 0);
            if (gizmoAxisX.selected)
                adjust.x = (gizmoAxisX.d - gizmoAxisX.lastD) * rotSensitivity / scale;
            if (gizmoAxisY.selected)
                adjust.y = -(gizmoAxisY.d - gizmoAxisY.lastD) * rotSensitivity / scale;
            if (gizmoAxisZ.selected)
                adjust.z = (gizmoAxisZ.d - gizmoAxisZ.lastD) * rotSensitivity / scale;

            moved = RotateNodes(adjust);
        }
        else if (editMode == EDIT_SCALE)
        {
            Vector3 adjust(0, 0, 0);
            if (gizmoAxisX.selected)
                adjust += Vector3(1, 0, 0) * (gizmoAxisX.t - gizmoAxisX.lastT);
            if (gizmoAxisY.selected)
                adjust += Vector3(0, 1, 0) * (gizmoAxisY.t - gizmoAxisY.lastT);
            if (gizmoAxisZ.selected)
                adjust += Vector3(0, 0, 1) * (gizmoAxisZ.t - gizmoAxisZ.lastT);

            // Special handling for uniform scale: use the unmodified X-axis movement only
            if (editMode == EDIT_SCALE && gizmoAxisX.selected && gizmoAxisY.selected && gizmoAxisZ.selected)
            {
                float x = gizmoAxisX.t - gizmoAxisX.lastT;
                adjust = Vector3(x, x, x);
            }

            moved = ScaleNodes(adjust);
        }

        if (moved)
        {
            GizmoMoved();
            UpdateNodeAttributes();
            needGizmoUndo = true;
        }
    }
    else
    {
        if (previousGizmoDrag)
            StoreGizmoEditActions();
    }

    previousGizmoDrag = drag;
}

bool IsGizmoSelected()
{
    return gizmo !is null && gizmo.enabled && (gizmoAxisX.selected || gizmoAxisY.selected || gizmoAxisZ.selected);
}

bool MoveNodes(Vector3 adjust)
{
    bool moved = false;

    if (adjust.length > M_EPSILON)
    {
        for (uint i = 0; i < editNodes.length; ++i)
        {
            if (moveSnap)
            {
                float moveStepScaled = moveStep * snapScale;
                adjust.x = Floor(adjust.x / moveStepScaled + 0.5) * moveStepScaled;
                adjust.y = Floor(adjust.y / moveStepScaled + 0.5) * moveStepScaled;
                adjust.z = Floor(adjust.z / moveStepScaled + 0.5) * moveStepScaled;
            }

            Node@ node = editNodes[i];
            Vector3 nodeAdjust = adjust;
            if (axisMode == AXIS_LOCAL && editNodes.length == 1)
                nodeAdjust = node.worldRotation * nodeAdjust;

            Vector3 worldPos = node.worldPosition;
            Vector3 oldPos = node.position;

            worldPos += nodeAdjust;

            if (node.parent is null)
                node.position = worldPos;
            else
                node.position = node.parent.WorldToLocal(worldPos);

            if (node.position != oldPos)
                moved = true;
        }
    }

    return moved;
}

bool RotateNodes(Vector3 adjust)
{
    bool moved = false;

    if (rotateSnap)
    {
        float rotateStepScaled = rotateStep * snapScale;
        adjust.x = Floor(adjust.x / rotateStepScaled + 0.5) * rotateStepScaled;
        adjust.y = Floor(adjust.y / rotateStepScaled + 0.5) * rotateStepScaled;
        adjust.z = Floor(adjust.z / rotateStepScaled + 0.5) * rotateStepScaled;
    }

    if (adjust.length > M_EPSILON)
    {
        moved = true;

        for (uint i = 0; i < editNodes.length; ++i)
        {
            Node@ node = editNodes[i];
            Quaternion rotQuat(adjust);
            if (axisMode == AXIS_LOCAL && editNodes.length == 1)
                node.rotation = node.rotation * rotQuat;
            else
            {
                Vector3 offset = node.worldPosition - gizmoAxisX.axisRay.origin;
                if (node.parent !is null && node.parent.worldRotation != Quaternion(1, 0, 0, 0))
                    rotQuat = node.parent.worldRotation.Inverse() * rotQuat * node.parent.worldRotation;
                node.rotation = rotQuat * node.rotation;
                Vector3 newPosition = gizmoAxisX.axisRay.origin + rotQuat * offset;
                if (node.parent !is null)
                    newPosition = node.parent.WorldToLocal(newPosition);
                node.position = newPosition;
            }
        }
    }

    return moved;
}

bool ScaleNodes(Vector3 adjust)
{
    bool moved = false;

    if (adjust.length > M_EPSILON)
    {
        for (uint i = 0; i < editNodes.length; ++i)
        {
            Node@ node = editNodes[i];

            Vector3 scale = node.scale;
            Vector3 oldScale = scale;

            if (!scaleSnap)
                scale += adjust;
            else
            {
                float scaleStepScaled = scaleStep * snapScale;
                if (adjust.x != 0)
                {
                    scale.x += adjust.x * scaleStepScaled;
                    scale.x = Floor(scale.x / scaleStepScaled + 0.5) * scaleStepScaled;
                }
                if (adjust.y != 0)
                {
                    scale.y += adjust.y * scaleStepScaled;
                    scale.y = Floor(scale.y / scaleStepScaled + 0.5) * scaleStepScaled;
                }
                if (adjust.z != 0)
                {
                    scale.z += adjust.z * scaleStepScaled;
                    scale.z = Floor(scale.z / scaleStepScaled + 0.5) * scaleStepScaled;
                }
            }

            if (scale != oldScale)
                moved = true;

            node.scale = scale;
        }
    }

    return moved;
}

void StoreGizmoEditActions()
{
    if (needGizmoUndo && editNodes.length > 0 && oldGizmoTransforms.length == editNodes.length)
    {
        EditActionGroup group;
        
        for (uint i = 0; i < editNodes.length; ++i)
        {
            EditNodeTransformAction action;
            action.Define(editNodes[i], oldGizmoTransforms[i]);
            group.actions.Push(action);
        }
        
        SaveEditActionGroup(group);
        SetSceneModified();
    }

    needGizmoUndo = false;
}