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How can I control the visibility of entities contained in block inserts?
Although this is a simple question for any experienced CAD user, it is nevertheless a concept that new CAD users have to understand and assimilate well before they can use CAD productively and control the DWG presentation the way they want it.
Before we go ahead and write about the solution, here is some more description of the question itself. We talk of visibility of entities here, more in the context of block inserts, rather than stand-alone DWG entities.
Layer State : Thawed/Frozen
Visibility control of stand-alone entities by freezing or thawing layers behaves straightforward: no entities that are located on frozen layers will display.
If the layer on which a block was inserted becomes frozen, then ALL content of that block will no longer be visible, regardless of the layer on which entities were located at creation time of the block.
If a block is inserted on a thawed layer, but contains content placed on a layer that becomes frozen, then only such content will no longer be visible.
Layer State : On/Off
The On/Off setting behaves different from the Thawed/Frozen setting, specifically concerning the behavior for block content placed on layer 0.
Entities that were on layer 0 at creation time of the block will obey the On/Off setting of the layer on which the block is inserted, so these elements will behave as is they were placed on the layer on which the block is inserted.
Entities that were not on layer 0 at creation time of a block, will obey the layer on/off setting in a normal way.
Example:
A block is made with entities from layers 0, 1 and 2. The block is inserted on layer 1.
Now, this is what happens:
- when we switch off layer 0: the block content that at block creation time was on layer 0, will remain visible because it now acts as if it were on layer 1!
- when we switch off layer 1: the block content that at block creation was on layer 0, becomes invisible,
as well as the block content that initially was on layer 1.
- when we switch off layer 2: only the block content that at creation time was on layer 2 becomes invisible.
- COLOR : The way the color of entities is controlled is related to this behavior: Entities that at block creation time were on layer 0 and had color property 'BYLAYER' will obey the color property of the layer on which the block is inserted.
More information
Background information extracted from Bricscad Help:
SETTING THE CURRENT ENTITY COLOR:
An entity's color determines how it is displayed and, if you are using a color printer, how it prints. Entities are created in the current color. There are 255 regular colors and two additional color properties that are often referred to as colors.
The two additional color properties are BYLAYER and BYBLOCK. These color properties cause an entity to adopt the color either of the layer or of the block into which it is inserted. BYLAYER is color number 256, and BYBLOCK is color number 0. In all commands where you would use a color, you can indicate BYLAYER and BYBLOCK as well as by numbers 256 and 0, respectively.
TO SET COLOR to BYLAYER:
To draw all entities in the default color set for the current layer, choose BYLAYER.
TO SET COLOR to BYBLOCK:
To draw entities in the default color (white or black, depending on your system settings) until they are grouped into a block, choose BYBLOCK.
After you insert the block into a drawing, it assumes the currently selected color for new entities.
If you insert a block that contains entities originally drawn on layer 0 and assigned color and linetype BYLAYER, it is placed on the current layer and assumes the color and linetype of that layer. If you insert a block that contains entities originally drawn on other layers or with explicitly specified colors or linetypes, the block retains the original settings.
If you insert a block that contains entities originally assigned color and linetype BYBLOCK, and the block itself has the color and linetype BYLAYER, those entities adopt the color and linetype of the layer onto which they are inserted. If the block is assigned an explicit color or linetype, such as red or dashed, those entities adopt those qualities.
If a block contains a mixture of colors, inserting blocks when the color is set to BYBLOCK can produce unpredictable results.
(Acknowledgements: Some inputs taken from www.bricsys.com knowledge-base articles)
Reproduced with permission on http://blog.bricsys.com .
Please do not reproduce on another blog/web-site without having sought explicit permission from the author. Instead, you may provide a hyper-link to this article from your blog.
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