Sketcher Workbench/pt-br

Introdução
A bancada de trabalho Sketcher Workbench do FreeCAD é usada para criar geometrias 2D destinadas ao uso na  PartDesign Workbench,  Arch Workbench, e outras bancadas de trabalho. Geralmente, um desenho 2D é considerado o ponto de partida para a maioria dos modelos CAD, pois um esboço 2D pode ser "extrudado" para criar uma forma 3D; outros esboços 2D podem ser usados para criar outros recursos como bolsos, saliências ou extrusões no topo das formas 3D previamente construídas. Junto com as operações booleanas definidas na Part Workbench, o Sketcher forma a base do método de Geometria Sólida Construtiva (constructive solid geometry - CSG) de construção de sólidos. Além disso, junto com as operações da PartDesign Workbench, o Sketcher também forma a base da metodologia de edição de recursos de criação de sólidos (feature editing).

A bancada do Sketcher apresenta restrições ("constraints"), permitindo que formas 2D sigam definições geométricas precisas em termos de comprimento, ângulos e relações (horizontalidade, verticalidade, perpendicularidade, etc.). Um solucionador de restrições calcula a extensão do efeito das restrições sobre a geometria 2D e permite a exploração interativa dos graus de liberdade do esboço.



Noções Básicas de Esboçagem por Restrições
Para explicar como o Sketcher funciona, pode ser útil compará-lo com a forma "tradicional" de desenho.

Desenho Tradicional
A forma tradicional de elaboração do CAD é herdada da antiga prancheta de desenho. As vistas ortogonais (2D) são desenhadas manualmente e destinadas à produção de desenhos técnicos (também conhecidos como plantas). Os objetos são desenhados precisamente no tamanho ou dimensão/cota pretendidos. Se você deseja desenhar uma linha horizontal de 100 mm de comprimento começando em (0,0), ative a ferramenta de linha, clique na tela ou insira as coordenadas (0,0) para o primeiro ponto e, em seguida, dê um segundo clique ou insira as coordenadas do segundo ponto em (100,0). Você também pode traçar sua linha em uma posição qualquer e movê-la depois. Quando terminar de desenhar as geometrias, basta adicionar as cotas.

Esboçagem por Restrições
O Sketcher afasta-se dessa lógica. Os objetos não precisam ser desenhados exatamente como se pretende, porque eles serão definidos posteriormente por restrições. Os objetos podem ser desenhados livremente e, desde que ainda não tenham restrições, podem ser modificados. Na verdade, eles estão "flutuando" e podem ser movidos, esticados, girados, redimensionados e assim por diante. Isso proporciona grande flexibilidade no processo de design.

O Que São Restrições?
Em vez de cotas, restrições são usadas para limitar os graus de liberdade de um objeto. Por exemplo, uma linha sem restrições tem 4 graus de liberdade - (em inglês, Degrees Of Freedom - abreviado como " DOF "): ela pode ser movida horizontal e verticalmente, pode ser estendida/encurtada, e pode ser rotacionada.

Aplicar uma restrição horizontal ou vertical, ou uma restrição angular (em relação a outra linha ou a um dos eixos), limitará sua capacidade de rotação, deixando-a com 3 graus de liberdade. Travar um de seus pontos em relação à origem removerá outros 2 graus de liberdade, e a aplicação de uma restrição de tamanho (dimensão) removerá o último grau de liberdade. A linha é então considerada totalmente restrita.

Vários objetos podem ser restringidos entre si. Duas linhas podem ser unidas por meio de um de seus pontos com a restrição de ponto coincidente. Um ângulo pode ser definido entre elas, ou elas podem ser postas como perpendiculares. Uma linha pode ser tangente a um arco ou círculo e assim por diante. Um esboço complexo com vários objetos terá uma série de soluções diferentes e torná-lo totalmente restrito significa que apenas uma dessas soluções possíveis foi alcançada com base nas restrições aplicadas.

Existem dois tipos de restrições: geométricas e dimensionais. Eles são detalhados na seção 'As Ferramentas' abaixo.

Para que o Sketcher não serve
O Sketcher não se destina à produção de plantas 2D. Depois que os esboços são usados para gerar um sólido, eles são automaticamente ocultados. As restrições são visíveis apenas no modo de edição de esboço.

Se você só precisa produzir visualizações 2D para impressão e não deseja criar modelos 3D, verifique a Draft workbench. Ao contrário dos elementos do Sketcher, os objetos Draft não usam restrições; estes são formas simples definidas no momento da sua criação. Tanto o Draft quanto o Sketcher podem ser usados para desenho de geometria 2D e criação de sólidos 3D, embora suas preferências de uso sejam diferentes; o Sketcher é normalmente usado junto com as bancadas Part e PartDesign para criar sólidos; Draft é normalmente usado para desenhos planos simples sobre uma grade, como ao desenhar uma planta baixa arquitetônica; nessas situações, o Draft é usado principalmente em conjunto com a Arch Workbench. A ferramenta Draft2Sketch converte um objeto Draft em um objeto Sketch e vice-versa; muitas ferramentas que requerem um elemento 2D como entrada funcionam com qualquer desses objetos, já que uma conversão interna é feita automaticamente.

Fluxo de Trabalho do Esboço
A Sketch is always 2-dimensional (2D). To create a solid, a 2D Sketch of a single enclosed area is created and then either Padded or Revolved to add the 3rd dimension, creating a 3D solid from the 2D Sketch.

If a Sketch has segments that cross one another, places where a Point is not directly on a segment, or places where there are gaps between endpoints of adjacent segments, Pad or Revolve won't create a solid. Sometimes a Sketch which contains lines which cross one another will work for a simple operation such as Pad, but later operations such as Linear Pattern will fail. It is best to avoid crossing lines. The exception to this rule is that it doesn't apply to Construction (blue) Geometry.

Inside the enclosed area we can have smaller non-overlapping areas. These will become voids when the 3D solid is created.

Once a Sketch is fully constrained, the Sketch features will turn green; Construction Geometry will remain blue. It is usually "finished" at this point and suitable for use in creating a 3D solid. However, once the Sketch dialog is closed it may be worthwhile going to Part Workbench and running  to ensure there are no features in the Sketch which may cause later problems.

As Ferramentas
As ferramentas da bancada Sketcher estão todas localizadas no menu Sketch que aparece quando você carrega a bancada.

General

 * [[Image:Sketcher_NewSketch.svg‎‎|32px]] New sketch: Creates‎ a new sketch on a selected face or plane. If no face is selected while this tool is executed the user is prompted to select a plane from a pop-up window.


 * [[Image:Sketcher_EditSketch.svg|32px]] Edit sketch: Edit the selected Sketch. This will open the Sketcher Dialog.


 * [[Image:Sketcher_LeaveSketch.svg|32px]] Leave sketch: Leave the Sketch editing mode.


 * [[Image:Sketcher_ViewSketch.svg|32px]] View sketch: Sets the model view perpendicular to the sketch plane.


 * [[Image:Sketcher_ViewSection.svg|32px]] View section: Creates a section plane that temporarily hides any matter in front of the sketch plane.


 * [[Image:Sketcher_MapSketch.svg|32px]] Map sketch to face: Maps a sketch to the previously selected face of a solid.


 * Sketcher_ReorientSketch.svg Reorient sketch: Allows you to attach the sketch to one of the main planes.


 * Sketcher_ValidateSketch.svg Validate sketch: Verify the tolerance of different points and adjust them.


 * [[Image:Sketcher_MergeSketches.svg|32px]] Merge sketches: Merge two or more sketches.


 * [[Image:Sketcher_MirrorSketch.svg|32px]] Mirror sketch: Mirror a sketch along the x-axis, the y-axis or the origin.


 * Sketcher_StopOperation.svg Stop operation: when in edit mode, stop the current operation, whether that is drawing, setting constraints, etc.

Sketcher geometries
These are tools for creating objects.


 * [[Image:Sketcher_CreatePoint.svg|32px]] Point: Draws a point.


 * [[Image:Sketcher_CreateLine.svg|32px]] Line: Draws a line segment between 2 points. Lines are infinite regarding certain constraints.


 * [[Image:Sketcher_CompCreateArc.png|48px]] Create an arc: This is an icon menu in the Sketcher toolbar that holds the following commands:


 * [[Image:Sketcher_CreateArc.svg|32px]] Arc: Draws an arc segment from center, radius, start angle and end angle.


 * [[Image:Sketcher_Create3PointArc.svg|32px]] Arc by 3 points: Draws an arc segment from two endpoints and another point on the circumference.


 * [[Image:Sketcher_CompCreateCircle.png|48px]] Create a circle: This is an icon menu in the Sketcher toolbar that holds the following commands:


 * [[Image:Sketcher_CreateCircle.svg|32px]] Circle: Draws a circle from center and radius.


 * [[Image:Sketcher_Create3PointCircle.svg|32px]] Circle by 3 points: Draws a circle from three points on the circumference.


 * [[Image:Sketcher_CompCreateConic.png|48px]] Create a conic: The sketcher provides the following conical sections. Unlike B-splines they can be used with all sorts of constraints such as tangents, point-on-object, or orthogonal.
 * [[Image:Sketcher_CreateEllipseByCenter.svg|32px]] Ellipse by center: Draws an ellipse by center point, major radius point and minor radius point.
 * [[Image:Sketcher_CreateEllipseBy3Points.svg|32px]] Ellipse by 3 points: Draws an ellipse by major diameter (2 points) and minor radius point.
 * [[Image:Sketcher_CreateArcOfEllipse.svg|32px]] Arc of ellipse: Draws an arc of ellipse by center point, major radius point, starting point and ending point.
 * [[Image:Sketcher_CreateArcOfHyperbola.svg|32px]] Arc of hyperbola: Draws an arc of hyperbola.
 * [[Image:Sketcher_CreateArcOfParabola.svg|32px]] Arc of parabola: Draws an arc of parabola.


 * [[Image:Sketcher_CompCreateBSpline.png|48px]] Create a B-spline: This is an icon menu in the Sketcher toolbar that holds the following commands:
 * Sketcher_CreateBSpline.svg Create B-spline: Draws a B-spline curve by its control points.
 * Sketcher_CreatePeriodicBSpline.svg Create periodic B-spline: Draws a periodic (closed) B-spline curve by its control points.


 * [[Image:Sketcher_CreatePolyline.svg|32px]] Polyline (multiple-point line): Draws a line made of multiple line segments. Pressing the M key while drawing a Polyline toggles between the different polyline modes.


 * [[Image:Sketcher_CreateRectangle.svg|32px]] Rectangle: Draws a rectangle from 2 opposite points.


 * [[Image:Sketcher_CompCreateRegularPolygon.png|48px]] Create regular polygon: This is an icon menu in the Sketcher toolbar that holds the following commands:


 * [[Image:Sketcher_CreateTriangle.svg|32px]] Triangle: Draws a regular triangle inscribed in a construction geometry circle.


 * [[Image:Sketcher_CreateSquare.svg|32px]] Square: Draws a regular square inscribed in a construction geometry circle.


 * [[Image:Sketcher_CreatePentagon.svg|32px]] Pentagon: Draws a regular pentagon inscribed in a construction geometry circle.


 * [[Image:Sketcher_CreateHexagon.svg|32px]] Hexagon: Draws a regular hexagon inscribed in a construction geometry circle.


 * [[Image:Sketcher_CreateHeptagon.svg|32px]] Heptagon: Draws a regular heptagon inscribed in a construction geometry circle.


 * [[Image:Sketcher_CreateOctagon.svg|32px]] Octagon: Draws a regular octagon inscribed in a construction geometry circle.


 * [[Image:Sketcher_CreateRegularPolygon.svg|32px]] Create Regular Polygon : Draws a regular polygon by selecting the number of sides and picking two points: the center and one corner.


 * [[Image:Sketcher_CreateSlot.svg|32px]] Slot: Draws an oval by selecting the center of one semicircle and an endpoint of the other semicircle.


 * [[Image:Sketcher_CreateFillet.svg|32px]] Fillet: Makes a fillet between two lines joined at one point. Select both lines or click on the corner point, then activate the tool.


 * [[Image:Sketcher_Trimming.svg|32px]] Trimming: Trims a line, circle or arc with respect to the clicked point.


 * Sketcher_Extend.svg Extend: Extends a line or an arc to a boundary line, arc, ellipse, arc of ellipse or a point in space.


 * [[Image:Sketcher_External.svg|32px]] External Geometry: Creates an edge linked to external geometry.


 * Sketcher_CarbonCopy.svg CarbonCopy: Copies the geometry of another sketch.


 * Sketcher_ToggleConstruction.svg Construction Mode: Toggles sketch geometry from/to construction mode. Construction geometry is shown in blue and is discarded outside of Sketch editing mode.

Sketcher constraints
Constraints are used to define lengths, set rules between sketch elements, and to lock the sketch along the vertical and horizontal axes. Some constraints require use of Helper constraints.

Geometric constraints
These constraints are not associated with numeric data.


 * Sketcher_ConstrainCoincident.svg Coincident: Affixes a point onto (coincident with) one or more other points.


 * Sketcher_ConstrainPointOnObject.svg Point On Object: Affixes a point onto another object such as a line, arc, or axis.


 * Sketcher_ConstrainVertical.svg Vertical: Constrains the selected lines or polyline elements to a true vertical orientation. More than one object can be selected before applying this constraint.


 * Sketcher_ConstrainHorizontal.svg Horizontal: Constrains the selected lines or polyline elements to a true horizontal orientation. More than one object can be selected before applying this constraint.


 * Sketcher_ConstrainParallel.svg Parallel: Constrains two or more lines parallel to one another.


 * Sketcher_ConstrainPerpendicular.svg Perpendicular: Constrains two lines perpendicular to one another, or constrains a line perpendicular to an arc endpoint.


 * Sketcher_ConstrainTangent.svg Tangent: Creates a tangent constraint between two selected entities, or a co-linear constraint between two line segments. A line segment does not have to lie directly on an arc or circle to be constrained tangent to that arc or circle.


 * Sketcher_ConstrainEqual.svg Equal: Constrains two selected entities equal to one another. If used on circles or arcs their radii will be set equal.


 * Sketcher_ConstrainSymmetric.svg Symmetric: Constrains two points symmetrically about a line, or constrains the first two selected points symmetrically about a third selected point.


 * [[Image:Sketcher_ConstrainBlock.svg|32px]] Block: it blocks an edge from moving, that is, it prevents its vertices from changing their current positions. It should be particularly useful to fix the position of B-Splines. See the Block Constraint forum topic.

Dimensional constraints
These are constraints associated with numeric data, for which you can use the expressions. The data may be taken from a spreadsheet.


 * Sketcher_ConstrainLock.svg Lock: Constrains the selected item by setting vertical and horizontal distances relative to the origin, thereby locking the location of that item. These constraint distances can be edited later.


 * Sketcher_ConstrainDistanceX.svg Horizontal distance: Fixes the horizontal distance between two points or line endpoints. If only one item is selected, the distance is set to the origin.


 * Sketcher_ConstrainDistanceY.svg Vertical distance: Fixes the vertical distance between 2 points or line endpoints. If only one item is selected, the distance is set to the origin.


 * Sketcher_ConstrainDistance.svg Distance: Defines the distance of a selected line by constraining its length, or defines the distance between two points by constraining the distance between them.


 * Sketcher_ConstrainRadius.svg Radius: defines the radius of a selected arc or circle by constraining the radius.
 * Sketcher_ConstrainDiameter.svg Diameter: defines the diameter of a selected arc or circle by constraining the radius.
 * Sketcher_ConstrainAngle.svg Angle: Defines the internal angle between two selected lines.


 * Sketcher_ConstrainSnellsLaw.svg Snell's Law: Constrains two lines to obey a refraction law to simulate the light going through an interface.


 * Sketcher_ConstrainInternalAlignment.svg Internal alignment: Aligns selected elements to selected shape (e.g. a line to become major axis of an ellipse).


 * Sketcher_ToggleDrivingConstraint.svg Toggle driving/reference constraint: Toggles the toolbar or the selected constraints to/from reference mode.


 * Sketcher_ToggleActiveConstraint.svg Activate/Deactivate constraint: enable or disable an already placed constraint.

Sketcher tools

 * Sketcher_SelectElementsWithDoFs.svg Select solver DOFs: Highlights in green the geometry with degrees of freedom (DOFs), i.e. not fully constrained.


 * Sketcher_CloseShape.svg Close Shape: Creates a closed shape by applying coincident constraints to endpoints


 * Sketcher_ConnectLines.svg Connect Edges: Connect sketcher elements by applying coincident constraints to endpoints


 * Sketcher_SelectConstraints.svg Select Constraints: Selects the constraints of a sketcher element


 * Sketcher_SelectElementsAssociatedWithConstraints.svg Select Elements Associated with constraints: Select sketcher elements associated with constraints


 * Sketcher_SelectRedundantConstraints.svg Select Redundant Constraints: Selects redundant constraints of a sketch


 * Sketcher_SelectConflictingConstraints.svg Select Conflicting Constraints: Selects conflicting constraints of a sketch


 * Sketcher_RestoreInternalAlignmentGeometry.svg Show/Hide internal geometry: Recreates missing/deletes unneeded internal geometry of a selected ellipse, arc of ellipse/hyperbola/parabola or B-spline.


 * Sketcher_SelectOrigin.svg Select Origin: Selects the origin of a sketch


 * Sketcher_SelectVerticalAxis.svg Select Vertical Axis: Selects the vertical axis of a sketch


 * Sketcher_SelectHorizontalAxis.svg Select Horizontal Axis: Selects the horizontal axis of a sketch


 * Sketcher_Symmetry.svg Symmetry: Copies a sketcher element symmetrical to a chosen line


 * Sketcher_Clone.svg Clone: Clones a sketcher element


 * Sketcher_Copy.svg Copy: Copies a sketcher element


 * Sketcher_Move.svg Move: Moves the selected geometry taking as reference the last selected point.


 * Sketcher_RectangularArray.svg Rectangular Array: Creates an array of selected sketcher elements


 * Sketcher_DeleteAllGeometry.svg Delete All Geometry: Deletes all geometry from the sketch.


 * Sketcher_DeleteAllConstraints.svg Delete All Constraints: Deletes all constraints from the sketch.

Sketcher B-spline tools

 * Sketcher_BSplineDegree.svg Show/hide B-spline degree


 * Sketcher_BSplinePolygon.svg Show/hide B-spline control polygon


 * Sketcher_BSplineComb.svg Show/hide B-spline curvature comb


 * Sketcher_BSplineKnotMultiplicity.svg Show/hide B-spline knot multiplicity


 * Sketcher_BSplinePoleWeight.svg Show/hide B-spline control point weight,


 * Sketcher_BSplineConvertToNURB.svg Convert geometry to B-spline


 * Sketcher_BSplineIncreaseDegree.svg Increase B-spline degree


 * Sketcher_BSplineDecreaseDegree.svg Decrease B-spline degree,


 * Sketcher_BSplineIncreaseKnotMultiplicity.svg Increase knot multiplicity


 * Sketcher_BSplineDecreaseKnotMultiplicity.svg Decrease knot multiplicity

Sketcher virtual space

 * Sketcher_SwitchVirtualSpace.svg Switch Virtual Space: Allows you to hide all constraints of a sketch and make them visible again.

Preferences

 * [[Image:Preferences-general.svg|32px]] Preferences: Preferences for the Sketcher workbench.

Melhores Práticas
Cada usuário CAD desenvolve sua própria maneira de trabalhar ao longo do tempo, mas existem alguns princípios gerais úteis a seguir.


 * A series of simple sketches is easier to manage than a single complex one. For example, a first sketch can be created for the base 3D feature (either a pad or a revolve), while a second one can contain holes or cutouts (pockets). Some details can be left out, to be realized later on as 3D features. You can choose to avoid fillets in your sketch if there are too many, and add them as a 3D feature.
 * Always create a closed profile, or your sketch won't produce a solid, but rather a set of open faces. If you don't want some of the objects to be included in the solid creation, turn them to construction elements with the Construction Mode tool.
 * Use the auto constraints feature to limit the number of constraints you'll have to add manually.
 * As a general rule, apply geometric constraints first, then dimensional constraints, and lock your sketch last. But remember: rules are made to be broken. If you're having trouble manipulating your sketch, it may be useful to constrain a few objects first before completing your profile.
 * If possible, center your sketch to the origin (0,0) with the lock constraint. If your sketch is not symmetric, locate one of its points to the origin, or choose nice round numbers for the lock distances. In v0.12, external constraints (constraining the sketch to existing 3D geometry like edges or to other sketches) are not implemented. This means that to locate following sketches geometry to your first sketch, you'll need to set distances relative to your first sketch manually. A lock constraint of (25,75) from the origin is more easily remembered than (23.47,73.02).
 * If you have the possibility to choose between the Length constraint and the Horizontal or Vertical Distance constraints, prefer the latter. Horizontal and Vertical Distance constraints are computationally cheaper.
 * In general, the best constraints to use are: Horizontal and Vertical Constraints; Horizontal and Vertical Length Constraints; Point-to-Point Tangency. If possible, limit the use of these: the general Length Constraint; Edge-to-Edge Tangency; Fix Point Onto a Line Constraint; Symmetry Constraint.
 * If in doubt about the validity of a sketch once it is complete (features turn green), close the Sketcher dialog, switch to the [[Image:Workbench_Part.svg|24px]] Part Workbench and run.

Tutoriais

 * Sketcher tutorial por chrisb. Este é um documento PDF de 70 páginas que serve como um manual detalhado para o desenhista. Ele explica os fundamentos do uso do Sketcher e dá muitos detalhes sobre a criação de formas geométricas e cada uma das restrições.
 * Basic Sketcher Tutorial para iniciantes.
 * Sketcher Micro Tutorial - Constraint Practices.
 * Sketcher requirement for a sketch Requisito Mínimo para um Esboço e Determinação Completa de um Esboço.