Manual/PartII/Edge and Face Tools
Wikipedia，自由的百科全书
Contents |
Edge and Face Tools边和面工具
A key issue in modelling is the necessity to add vertices in certain zones of the mesh, and this is often regarded as splitting, or adding, edges in a given region. Many Edge Tools are grouped in a menu which is linked to KKEY Hotkey (Loop/Cut Menu.), but each individual tool has its own hotkey as well.
制作模型的一必要的问题就是在网格的特定区域增加点.而且这时常被视为分离或增加一个边在给定的区域.边框工具都聚合在一个菜单内,利用快捷键K(Loop/Cut Menu.)打开, 但是也有个别的工具有自己特定的快捷方式。
Edge select边的选择
In EditMode there are a few ways to select Edges: implicitly, explicitly, looping or by Region Selection. Implicit means you describe a more complex element using less complex elements. For example, to describe an edge you need to specify two vertices and to describe a face you need to specify three or more vertices or three or more edges. 在"EditMode"有几种办法可以选择“边”：
Looping is a process of selecting edges and faces based on an algorithm of how they are related to each other.
Region Selection is a tool that allows selection of edges and faces based on an intersection with a circular 2D region.
Explicit Edge Selection
To select an edge use Edge select mode and the RMB. To select additional edges use SHIFT-RMB.
显式边选择
To select an edge use Edge select mode and the RMB. To select additional edges use SHIFT-RMB.
Implicit Edge Selection
The other way to select an Edge is to select two vertices that bound the edge of interest. You are implying which edge by selecting its bounding vertices. To select an Edge implicitly use the Vertex select mode (Select modes.) in combination with RMB and/or SHIFT-RMB. (Implicit Edge selection) shows an edge selected on a cube using vertices --the cube of the left. The cube on the right is what shows when you switch to Edge select mode.
Edge Selection by looping
You can also select edges by using the edge loop select tool Template:AMB in any of the select modes (Select modes). This will select a row of edges that are connected in a line end to end. The algorithm for selection is as follows:
- First check to see if the selected element connects to only 3 other edges.
- If the edge in question has already been added to the list, the selection ends.
- Of the 3 edges that connect to the current edge, the ones that share a face with the current edge are eliminated and the remaining edge is added to the list and is made the current edge.
An example is easily shown in (Longitude/Latitude edge selection.) The left sphere shows an edge that was selected longitudinally. Notice how the loop is open. This is because the algorithm hit the vertices at the poles and terminated because the edge at the pole connects to more than 3 other edges. However, the right sphere shows an edge that was selected latitudinally and has formed a closed loop. This is because the algorithm hit the first edge that it started with.
You can add more edges by using Template:SAMB.
Face select
In EditMode there are a few ways to select Faces: implicitly, explicitly, looping or by region. Implicit means you describe a more complex element using less complex elements. For example, to describe an edge you need to specify two vertices and to describe a face you need to specify three or more vertices or three or more edges.
Explicit Face Selection
To select a face use Face select mode (Select modes.) and the RMB. To select additional faces use SHIFT-RMB.
Implicit Face Selection
There are several ways to implicitly select face(s). The first is to select four vertices that bound the face of interest. You are implying which face by selecting its bounding vertices. To select a Face implicitly use either Vertex select mode or Edge select mode; see (Select modes.) in combination with RMB and/or SHIFT-RMB. (Implicit Face selection) shows a face selected on a cube using vertices --the cube of the left. The cube on the right is what shows when you switch to Face select mode.
You can also implicitly select face(s) by selecting the bounding edges of the face of interest. This will produce the same results as selecting vertices.
Face Selection by looping
It is also possible to use a slightly different looping algorithm based on faces by using Template:CAMB. This will select a row of faces that are connected in a line along their opposite edges. The algorithm is as follows:
- A face loop is made by two neighbouring edge loops.
- Extends only to quadrilateral faces.
- Ends when a triangular face is met (and the two bounding edgeloops merge into one).
(Alt verses Ctrl-Alt) shows an example of the two different algorithms. The same edge was selected but two different "groups of edges" where generated. One is based on edges during computation and the other is based on faces.
The differences in the algorithms becomes more apparent when you are in Vertex select mode, see (Alt verses Ctrl-Alt Vertex Mode). The edges selected in the grid labeled "Alt-RMB" is a result of using the edge algorithm Template:AMB verses the face algorithm Template:CAMB. The right grid clearly shows that faces where used to influence the resulting generated selection.
The algorithms are heavily influenced by what select mode you are in (Select modes.). Remember that the results is based on the select mode but the algorithm is driven by what key combination you use; Template:AMB or Template:CAMB.
Here is an example of selecting a latitude edge labeled "E" while in Vertex select mode; the edge is circled in white. As you can see the two algorithms produce completely different results. The left sphere has vertices selected based on the edge algorithm. The right sphere has more vertices selected based on the face algorithm. Note that in both cases the generated results of the algorithm was vertices because we were in Vertex select mode. And if you switch to Face select mode you will see the corresponding faces. Note that the area surrounded by the vertices are drawn in a translucent color indicating the potential faces implied by the selected vertices.
However, had we had been in Edge select mode the generated results would have been selected edges and if you switched to Face select mode you would not see any faces selected. Be aware of what select mode you are in when applying the two types of algorithms.
Face Loop Splitting
The Loop tool allows you to split a loop of faces. This loop is defined using the same algorithm as described in the sections Edge Selection by looping and Face Selection by looping. The tool is only available in EditMode and to activate it press CTRL-R. The tool functions in all Edit Select Modes.
This tool is interactive such that as you move the cursor over valid edges a magenta colored edge loop, or loop line, appears (Loop Split Activated) at the mid-section of the valid edge. A valid edge is an edge that satifies the looping algorithms previously described.
Upon initial activation of the tool 3D window header changes to show the "Number of Cuts" (Initial Loop Split header). At this point, before selecting an edge, you can change the number of cuts generated by either the keyboard or MW; with the maximum cuts allowed set at 130. These cuts run parallel with the face loop line.
By default, new vertices for the new edge loop are placed exactly on the pre-existing edges. This keeps subdivided faces flat. If a smoother result is desired the SKEY can be used at this point. If smooth mode is on then new vertices are not placed on the previous edge but displaced in the direction of the "normal to the edge" by a given percentage.
In (Loop Split Activated) the cursor was located where the white circle is located. This caused the loop line to appear at the mid point of the edge. As you can see the loop stops at the poles because the edges at the poles have more than 3 connecting edges.
| Warning: *** START This section needs further updates to version 2.4. *** |
??? Pop up. 2.4 dose not have this. ??? Manual-Part-II-EdgeFaceLoop3.png ...
| Warning: *** END This section needs further updates to version 2.4. *** |
Once an edge is chosen via LMB, the edge is highlighted in green (Loop Split edge selected). At this point you have a number of actions you can perform:
- You can change the selected edge along the edge loop line by using the MW, or the Left and Right arrows.
- You can switch between Proportional and Percentage modes with the PKEY. The default mode is Percentage.
- You can move/slide the edge loop line in between the face loop by moving the mouse.
- You can control the precision of the sliding along the edge with either the CTRL or SHIFT key. CTRL limits movement to 10% steps per move. SHIFT controls precision even further by limiting movement to 1% steps per move in either Select mode. The default is 5% steps per move.
The last step is to click LMB to complete the splitting process, all faces and internal edges of the face loop are split based on the initial "number of cuts". By default the "number of cuts" is "1" which means the edges will be split in half at the intersections highlighted by the edge loop line. (Loop Split edge completed) shows the new faces and edges, "A" an "B". The view is rotated so that the new faces and edges are clearly visible from the top of the sphere.
In order to explain Proportional and Percentage modes we are going to use a very simple mesh layed out like a 2x9 grid, (Loop Example Grid). The vertices at "A" and "D" have been moved in order to emphasize the difference between the two modes. The vertices at the level "C" and "B" remain unchanged. "E" is an area of interest when looking at Proportional mode.
Percentage Face Loop Splitting
In Percentage mode the 3D window header changes to (Percentage header) showing a number between -1 and 1 with 0 representing 50% or midway between.
As you move the mouse the percentage changes and the edge loop line, drawn in yellow, moves as a percentage of the distance between the edge marked in green as shown in (25% between), (Mid-way) and (89% between).
 25% between. |  Mid-way. |  89% between. |
What is important to realize here is that the yellow loop line is always the same percentage in distance for all vertices bounded by the face loop. For example, looking at (Mid-way) you can see that the yellow loop line is 50% the distance between each vertex regardless of how far the vertices are from each other. The yellow loop line is 50%, in distance, between vertex "A" and "B" and it is also 50% between vertex "C" and "D".
For (25% between) you can see that the yellow line loop is always 25% along the distance to the next vertex on each edge.
Proportional Face Loop Splitting
Proportional face loop splitting keeps the shape of the newly cut edge loop the same as one of the edge loops that it cuts between, rather than cutting at a percentage along each perpendicular edge. Each edge is divided into two parts which are proportional to one another.
In Proportional mode the 3D window header changes to (Proportional header) showing the position along the length of the currently selected edge which is marked in green. Movement is restricted to this length. As you move the mouse the length indicator in the header changes showing where along the length of the edge you are.
Unlike Percentage mode, Proportional mode treats the edge as having a start and end vertex with the start marked by an enlarged vertex decorator; see (Vertex Marker). The start vertex, labeled as "A", can be flipped to the opposite vertex using the FKEY; see (Vertex Marker Opposite).
 Vertex Marker. |  Vertex Marker Opposite. |
By moving the mouse the edge loop line moves towards or away from the start vertex. But the loop line will only move as far as the length of the currently selected edge. If the current edge is shorter than any of the other edges then movement will be limited to the short edge. (Proportional Range) shows an example of how the distance is restricted by the length of the currently edge, labeled "B". Looking at Label "A" you can see that the line loop moved the same distance. If the line only moves 0.2 units on the selected edge then the line only moves 0.2 units everywhere else in the face loop region.
Also notice that the portion of the line loop labeled "A" hasn't gone all the way to the "bottom"; that is because the selected edge is only 0.25 units in length. Hence the line portion at "A" will not be able to move more than 0.25 units down because the range of movement is restricted to the length of the selected edge.
(Proportional Range Flipped) is another example where the start vertex has been flipped while using the same selected egde as compared to (Proportional Range). You can see that movement is still restricted to the length of the selected edge. In this example the yellow edge loop line stays straight because the maximum range takes the edge loop line to the lowest vertex and hence the line will be straight.
Edge Loop Delete
The Edge delete tool allows you to delete an edge-loop if it is between two other edge-loops. This tool can be activated via the Erase/Delete menu, XKEY, and selecting "Edge Loop" from the menu; see (Erase Menu). This will create one face-loop where two previously existed.
The same type of restrictions apply to selecting edge-loops as applied to sliding edges. For example, you can't select two edges that are in different edge-loops. See Edge Slide restrictions for further details on the restrictions.
| Note: Deleting edge-loops is completely different than deleting edges that look like an edge-loop. By deleting an edge-loop, other edge-loops combine together to preserve the surface of the mesh. By deleting a chain of edges, that look like an edge-loop, the edges are actually deleted which means faces will be deleted as well. This will leave holes in the mesh where the faces once were. |
In the following images, you can see what happens when an edge-loop is deleted from a UV Sphere:
 Before edgeloop delete. |  After edgeloop delete. |
As you can see, the edge-loop has been deleted but the faces have been merged with the surrounding edges. If you had deleted the edges using "Edges" from the (Erase Menu) you would have a band of deleted faces all the way around the sphere. Which is quite different than using "Edge Loop".
Knife Tool/Cut Type
The Knife Tool works by subdividing selected edges intersected by a user-drawn 'knife' line. For example, if you wish to cut a hole in the front of a sphere, you select only the front edges, and then draw a line with the mouse. The tool only works with edges; selected either implicitly or explicitly.
To test the tool add a Grid Mesh. By default you will be in EditMode with all the vertices selected. Press SHIFT-K to activate (Knife Tool/Cut Type). You are prompted to choose how the cut will be interpreted:
- Exact Line will divide the edges exactly where the knife line crosses them.
- Midpoints divides an intersected edge at its midpoint.
- Multicut allows the user to subdivide the mesh several times at once. This style has an additional input allowing you to select the number of cuts.
Regardless of the style you choose, the cursor has now changed to an icon of a scalpel and the 3DWindow header has changed to (Knife Tool 3DWindow header). You can draw straight lines by clicking LMB and moving repeatedly or you can create freehand lines by pressing and holding LMB while dragging. MMB constrains drawing to an axis as expected.
The polylines can be drawn with an arbitrary number of segments, but the intersection routines only detect one crossing per edge. Crossing back over an edge multiple times does not perform additional cuts on it.
When you have finished drawing your line, you can either hit ENTER or CTRL-ENTER to confirm the cut or ESCAPE or RMB at any time to cancel the operation.
- ENTER will select every edge except the new edges created from the cut.
- CTRL-ENTER will select only the new edges created from the cut. Note, only edges that intersect the hand-drawn selected edges are selected.
Snap to grid is not currently implemented, but is being looked at for future releases.
| Note:
With a large mesh, it will be quicker to select a smaller number of vertices, those defining only the edges you plan to split since the Knife will save time in testing selected vertices for knife trail crossings. |
Exact Line Cut Type
(ExactLine before and after) is an example of using the 'Exact Line' knife. The cut is determined from the hand-drawn line labeled "A" in the grid labeled "Drawing".
The grid labeled "Enter" is the result of hitting the ENTER key. As you can see the intersections on the edges of the cube are where the drawn line actually intersects, no matter how wiggly the line is. In addition, all the edges have been selected other than the newly created edges from the cut tool itself.
The grid labeled "Ctrl-Enter" is the result of hitting CTRL-ENTER. In this case only the newly created edges, "B" and "C", are hightlighted while edge "D" is not. "D" is a secondary edge as a result of the cut tool.
Midpoints Cut Type
(Midpoints before and after) is an example of using the 'Midpoints Line' knife. The cut is determined from the hand-drawn line labeled "A" in the grid labeled "Drawing". Notice how the line labeled "A" intersects the right edge twice; only the first intersection will be considered during the cut.
The grid labeled "Enter" is the result of hitting the ENTER key. As you can see the intersections on the edges of the cube are the mid points of each edge, no matter how wiggly the line is. In addition, all the edges have been selected other than the newly created edges from the cut tool itself.
The grid labeled "Ctrl-Enter" is the result of hitting CTRL-ENTER. In this case only the newly created edges, "B" and "C", are hightlighted while edge "D" is not. "D" is a secondary edge as a result of the cut tool.
MultiCut Type
When first entering this tool a popup dialog appears asking for the "Number of Cuts"; see (Number of Cuts). The default is "2". You are indicating how many equally spaced cuts the tool should make for each intersecting edge. For example, the default of "2" generates two intersections or three new edges for each intersection of the hand-drawn line, all of which are equally spaced in distance.
Also, if the "Beauty" option is toggled in the Edit Buttons, selected faces are only subdivided along the longest 2 sides. And, if both the "Beauty" and "Short" options are toggled, selected faces are only subdivided along the shortest 2 sides.
| Note: Using Edge select mode to select only the edges you wish to subdivide creates a more accurate subdivision than using the "Beauty" toggle. |
(MultiCut before and after) is an example of using the 'MultiCut' knife. The cut is determined from the hand-drawn line labeled "A" in the grid labeled "Drawing", while using the default "2" as the number of cuts. The line was drawn so that it intensionally intersected three edges.
The grid labeled "Enter" is the result of hitting the ENTER key. As you can see there are two cuts equally spaced on each edge intersected by the hand-drawn line; labeled "A", "B" and "C". "D" is a secondary edge as a result of the cut tool. The grid labeled "Ctrl-Enter" is the result of hitting CTRL-ENTER. In this case only the newly created edges are hightlighted while edge "D" is not.
Special Edge Tools
Edge editing includes some special tools that enhance the standard set called Edge Specials that can be accessed using CTRL-E; see (Edge Specials menu). These are:
- Mark Seam is used for UV mapping.
- Clear Seam is also used for UV mapping. For more on the usage of Seams see materials_uv_textures_lscm.
- Rotate Edge CW rotates edges or faces in a clockwise direction.
- Rotate Edge CCW rotates edges or faces in a counter clockwise direction.
- Loopcut see Face Loop Splitting.
- Edge Slide allows you to slide an edge along its two adjacent faces.
Rotate Edge CW/Rotate Edge CCW
To rotate an edge you need to select one edge or two adjacent faces. To select an edge you can use any of the three Edit Selection Modes. For example, you could select an edge by selecting the edge's adjacent vertices (implicit), selecting the edge itself (explicit) or selecting the two adjacent faces (implicit). Once the edge is selected you can apply Rotate Edge CW or Rotate Edge CCW to rotate clockwise or counter clockwise. See (Selected Edge Rotated CW and CCW.) for an edge selected explicitly using the Edge Selection Mode.
Be aware that sometimes, as shown in (Selected Edge Rotated CW and CCW.) and indicated with a T, that you could produce what appears to be "T" junctions/nodes by using this tool. However, Blender has created additional edges that prevent cracks in the mesh. You can prove this by selecting the vertex at the T and moving it around while noting that there are two edges now instead of one long edge.
| Note: See mesh_modelling_editmode_modes for more on selection modes. |
To rotate an edge based on faces you must to select two faces, (Adjacent selected Faces.), otherwise Blender notifies you with an error dialog, "ERROR: Select one edge or two adjacent faces." Applying either Rotate Edge CW or Rotate Edge CCW will produce exactly the same results as if you had selected the common edge shown in (Selected Edge Rotated CW and CCW.).
Edge Slide
Edge Slide allows you to slide one or more edges along faces adjacent to the selected edge(s) with a few restrictions involving the selection of edges. The tool is activated using CTRL-E and then selecting Edge slide. As with Face_loop_splitting this tool has both a Percentage and Proportional mode. The mode is displayed in the 3D window header. These modes behave the same as in Face loop splitting including all keys for controlling precision edge movement. To cancel this tool use RMB or ESCAPE.
(Simple edge slide.) is an example of sliding an edge along an extruded box. The selected edge is labeled "E" and the adjacent faces to that edge are "F1" and "F2". In "Edge moving", the tool has been activated and the edge is being slid along the edge drawn in green. Use LMB to complete the move as shown in "Moved".
Edge Slide restrictions
As mentioned there are restrictions when selecting edge(s). Invalid selections are:
- "Loop crosses itself". This means that the tool could not find any suitable faces that were adjacent to the selected edge(s). (Loop Crosses) is an example that shows this by selecting two edges that share the same face. A face can not be adjacent to itself.
- "Was not a single edge loop". Mostly likely you have selected edges that don't share the same edge loop. (Single Edges) is an example where the selected edges are not in the same edge loop which means they don't have a common edge. You can minimize this error by always selecting edges end to end or in a "Chain".
- "Could not order loop". This means the tool could not find an edge loop based on the selected edge(s). (Order loop) is an example where a single edge was selected in a 2D Plane object. An edge loop can not be found because there is only one face.
 Loop Crosses. |  Single Edges. |  Order loop. |
A "general" rule of thumb is that if multiple edges are selected they should be connected end to end such that they form a "continuous" chain. This is literally a general rule because you can still select edges in a chain that are invalid because some of the edges in the chain are in different edge loops. (Loop Crosses) is just such an example where the selected edges form a chain but they are not in the same edge loop.
If you select multiple edges just make sure they are connected. This will decrease the possibility of getting looping errors.
Bevelling Tools
A bevel is something that smooths out a sharp edge or corner. True world edges are very seldom exactly sharp. Not even a knife blade edge can be considered perfectly sharp. Most edges are intentionally bevelled for mechanical and practical reasons.
The Bevel tool is still under heavy development and the current implementation is rather crude since all edges in a given mesh are bevelled. There's no control over edges you want to keep sharp, or edges on nearly flat surfaces, which you don't need to bevel at all.
The Bevel tool can be used in EditMode, and can be accessed via the WKEY menu, where the Specials menu entry reads Bevel; see (Specials menu). Once selected, a popup asks for the number of recursions in the bevel, 
. If it is one, then each face is reduced in size and each edge becomes a single new face.
Tri and Quad faces are created as necessary at the corresponding vertices. If the Recursion number is greater than one, then the aforementioned procedure is applied that number of times. Hence, for a Recurs of 2 each edge is transformed into 4 edges, three new faces appear at the edge while smoothing the original edge. In general the number of new edges is 2 elevated to the Recurs power.
| Note Vertex count:
Remember that for each new edge two new vertices are created, with additional vertices created at the intersection between edges. This means your vertex count can quickly become enormous if you bevel with a high recursion! |
Once the tool is activated the 3D window header changes to show the bevel scaling size; (Bevel window header).
(Bevelling a cube) is an example of bevelling a cube with a Recurs of "2". Once the Recurs number is set each face of the mesh receives a yellow highlight. The cube labeled "Bevelling" is the tool in action. By moving the mouse pointer, the yellow highlights will shrink or grow or scale inwards or outwards; with the current scaling factor displayed on the 3D window header; see (Bevel window header). The yellow highlights will not scale beyond the volume of the object.
You can control the scaling to a finer degree by either pressing and holding CTRL, to scale in 0.1 steps, or by pressing and holding SHIFT to scale in 0.001 steps. LMB finalizes the operation, RMB or ESC aborts the action.
Alternatively, you can manually enter a scaling value by pressing SPACE. A popup dialog appears, 
, asking you to type in the beveling scale factor labeled as "Width". The scale is limited to a range from 0.0 to 10.0 and upon hitting "OK" the bevel action is completed.
The final result can be seen in the grid labeled "Beveled" or "Shaded".
|
