Part 1, the basics of hatching
We add hatching in AutoCAD to fill an enclosed area with a pattern, solid fill or gradient. Use hatch to represent materials, to detail sections (differentiate parts) or to show different zones. Hatches and fills add visual clarity and supply a method to get areas (and other properties). Hatching is not specific to one industry. It is used in all types of drawings.
The process:
- Close the area
- Start the hatch command
- Select the pattern or fill
- Pick the area to hatch.
- Adjust the properties
- Apply
Getting started
Before you add a hatch, you must have a closed area to hatch. You may need to add geometry to create a hatchable region.
When the command is active (or you have hatch selected), the Hatch Creation contextual tab appears. This provides the tools you need to create and edit the hatch.
To get a proper preview, choose the pattern before selecting the hatch area.
Picking a point inside an area is the default. The area can be bounded by a collection of object types. The objects do not need to be continuous and can overlap. The only condition is that there must be no gaps. In other words, a watertight area with no way for the hatch to leak out.
What if you don’t have a seamless enclosed area? That can still work. Use the Gap Tolerance to set the maximum gap size that AutoCAD could ignore and treat the area as closed. The only catch is that using a Gap Tolerance creates a non-associative hatch. More on that later.
Use the Select objects choice to select single, closed objects. Objects like circles, ellipses and (closed) polylines to fill the object’s area with a hatch. You can select multiple objects, including selecting by window and crossing. AutoCAD ignores non-closed objects.
You can mix methods, toggling selection modes from the command line or with the ribbon options. Use Remove Boundaries to remove hatch patterns added during the active command.
AutoCAD applies a single hatch object to all the selected areas. If wanting distinct objects per area enable Create Separate Hatches. Then you could change the properties of specific areas.
As with all new objects, AutoCAD creates hatch on the current layer. However, use the HPLAYER system variable to specify a default layer. AutoCAD then uses this layer for the hatch, regardless of the current layer.
Hatch Properties
You can adjust the hatch’s properties before and after picking the hatching area(s). This supports the workflow of setting the properties to get a suitable preview as you select the areas. Then, tweak the properties for the desired look before applying and creating the hatch.
Let’s look a hatch that is a pattern. We look at fills, part of the Hatch command, which fill and area with a solid color or gradient, in the next article.
The hatch fill is a pattern, solid, gradient or a user defined pattern.
Apply solid hatches when wanting to fill an area with a single, consistent color. It uses the active layer’s color (BYLAYER) by default but you can select another color if you wish.
AutoCAD includes dozens of predefined, industry-standard patterns to select from. You can also add your own pattern. More on this later.
You can adjust the scale and angle of a hatch pattern. With patterns and solids, you can use Transparency to make the hatch translucent. In addition to the hatch color, set a background color. This applies a solid fill behind the selected pattern.
AutoCAD limits the number of hatch lines to prevent memory and performance problems. If you hit his limit and need more hatch lines than AutoCAD is allowing, you can raise the value in the HPMAXLINES system variable.
Use the Draw Order to set the position of the hatch compared to other objects in the drawing. Place the hatch behind or in front all other objects or behind or in front of the hatch boundary.
Pro Tip: Use the OSOPTIONS system variable to manage how object snaps work with hatch objects.
Islands in the stream
When selecting objects AutoCAD, applies the hatch over the objects inside its area. Selecting an object inside the other one creates an island that the hatch goes around.
Selecting the hatched area by picking points is like pouring water into a basin. If there are objects in the basin the water goes around the objects. Hatch is the same. If you pick in an area and AutoCAD finds an enclosed area within the region the hatch goes around it.
AutoCAD treats enclosed areas and text objects inside hatch boundaries as islands.
With the Normal Island Detection, islands are not hatched but islands (lakes?) within islands are hatched.
Outer detection hatches only the area between the outer boundary and the interior islands. Use Ignore to hatch inward from the outermost hatch boundary ignoring the interior objects.
Boundaries and associativity
The boundary is the closed shape defining the area you want hatched. Hatch fills this enclosed boundary and will not extend past it.
When selecting objects to be hatched, the object itself becomes the boundary. When picking points, AutoCAD creates an invisible boundary defining the area.
When editing the hatch, use Display Boundary Objects to select the objects forming the boundaries. This is quicker than selecting the objects individually. You can then use the grips to edit the boundary.
By default, hatch is bounded and associated with its boundary. This means that as the boundary changes and if it stays closed, the hatch will update to match.
When selecting an associative hatch, only a single hatch grip displays. Use this grip to move the hatch’s origin and to dynamically adjust the scale and rotation.
Hatch can be unbounded. These non-associative hatches do not update when the original boundary changes. You will find non-associative hatches in old drawings or drawings imported from another application. It also happens when breaking the original boundary or if someone has turned off the Associative option.
When selecting non-associative hatch, the hatch grip and the boundary grips show.
Regardless of whether a hatch is bounded or unbounded, you can use Recreate to generate a polyline or region (your choice) about the selected hatch. Associate the new object with the hatch when wanting the new object to become the boundary. This is also the method to make a non-associative hatch into an associative hatch.
By not associating the hatch with the new object, you are free to move and manipulate the object without effecting the hatch. This is a great way to create the shape enclosing the hatch.
By using the Don’t Retain Boundaries options, you can have AutoCAD generate a polyline or region boundary as it creates the hatch. In these instances, the hatch becomes associative with the new boundary object.
Fun fact: You can trim non-associative hatch!
Annotative
AutoCAD’s Annotation Scale helps you keep consistent and readable annotations in your drawings—no matter the object size or the viewport scale.
A hatch is an object type that will scale based on the annotation scale. Read about annotation scale in detail in a previous article.
Hatch origin
AutoCAD uses the active UCS’ origin point and orientation to align and orient the hatch pattern which works fine most of the time — but not always. Use Set Origin to pick the origin and set the hatch pattern starting point.
In this example, note that the original orientation of the brick is not realistic. No one would start at the bottom with part of a brick. By changing the origin, the pattern starts at the selected point in the lower left corner of the region.
The expanded panel provides a series of predefined origin points. Like Top Right, which sets the origin at the top-right corner of the extents of the hatch. Note that even if the hatched area is not rectangular, AutoCAD still uses the rectangular extents of the hatch area.
Use Store as Default Origin to use the newly selected origin as the origin for all subsequent hatches.
Remember that AutoCAD uses the active UCS to orient the hatch. There may be some instances where it is easier to move or rotate the UCS before creating the hatch, such as when you want to align the hatch with an existing object.
To be continued…
