Using blocks and layers

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Using blocks and layers

Postby terrytmp » Thu Jan 16, 2014 1:44 am

Hi,

I'm just starting out using QCAD (and CAD in general) to design a garden shed (while dusting off memories from 20+ years ago of technical drawing at school).

Using QCAD I've been combining elements into blocks of parts before placing them into layers but feel like I'm missing something about how blocks and layers relate.

I've got a layer for the roof section, a layer for the front, another for the side elevation. I'd been drawing parts on the relevant layer and selecting them to create a block. Then at some point I noticed that strange things happened when making some layers visible, some parts would appear when they shouldn't and others disappear when they shouldn't (AFAICT). Then I noticed that some lines within blocks were allocated to a different layer than the block was, and that allocating them to layer 0 seemed to fix it.

I then proceeded to make sure the lines of each block were set to layer 0. I came unstuck with this method however when I then wanted to draw some of the hidden lines of parts as dashed rather than solid lines. I then had to break my all-lines-in-block-on-layer-0 rule in order to achieve the desired linestyle.

Uh. An idea just ocurred to me, probably from viewing viewtopic.php?f=47&t=1992 - I should create some layers purely for use within a block, but no drawing should otherwise go there - Outline, Center, Hidden etc, while other layers might be for major elements of the design - Roof, Base, Wall, Door, etc. That makes more sense anyway than how I was looking at it..

Just curious also if one generally splits the elevations into different layers or combines them into a single elevation (ie roof vs roof-plan roof-south etc)?

Also, I sometimes create a block for a part and then later realise that some other part will partially obscure the first part and then have to go back and edit the lines to change them to hidden lines, or I need to duplicate the block because not all will need changing. Is there a way for QCAD detect when an object is hidden and change the line style accordingly?

Thanks,
Terry.

PS, "duplicate block" would be useful.
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Re: Using blocks and layers

Postby Husky » Thu Jan 16, 2014 5:34 am

Hi Terry,

terrytmp wrote:Uh. An idea just ocurred to me, probably from viewing viewtopic.php?f=47&t=1992

That's a good start! :wink:

terrytmp wrote:I should create some layers purely for use within a block, but no drawing should otherwise go there - Outline, Center, Hidden etc, while other layers might be for major elements of the design - Roof, Base, Wall, Door, etc. That makes more sense anyway than how I was looking at it..

You could do that ... but the common praxis to work with layer is much more simple.
Try to think on this way:
Your drawing has a layer just for the Outlines,
also a layer just for Centerlines,
and one just for Hidden lines.
Now you can draw your Roof on a Layer called "Roof" and you can use for all the different Lines the predefined Layers "Outline", "Centerline", "Hidden lines".
If you are now in need to make your Roof invisible - just switch the Layer "Roof" to invisible. You are not in need to switch all ("Outline", "Centerline", "Hidden lines") used layer separately invisible. Everything what belongs to "Roof" will be invisible.

terrytmp wrote:Also, I sometimes create a block for a part and then later realise that some other part will partially obscure the first part and then have to go back and edit the lines to change them to hidden lines, or I need to duplicate the block because not all will need changing. Is there a way for QCAD detect when an object is hidden and change the line style accordingly?

No. There is no automatic way that QCAD will detect and decide which line has a hidden or not hidden status. Common praxis is to create a block which has to fit in most situations. If you need to conform just a single situation you can insert the block - explode the block - and customize this "Ex"-Block until its fits. If you see that you need this customized "Ex"-Block a couple times in your drawing I would suggest to create an additional Block.[/quote]

terrytmp wrote:PS, "duplicate block" would be useful.
Use your already existing Block as basis - insert this block in your drawing - explode this block - change this Ex-block as you need it - save it as a new Block - done :wink:
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Re: Using blocks and layers

Postby terrytmp » Thu Jan 16, 2014 11:07 am

Husky wrote:Hi Terry,
terrytmp wrote:I should create some layers purely for use within a block, but no drawing should otherwise go there - Outline, Center, Hidden etc, while other layers might be for major elements of the design - Roof, Base, Wall, Door, etc. That makes more sense anyway than how I was looking at it..

You could do that ... but the common praxis to work with layer is much more simple.
Try to think on this way:
Your drawing has a layer just for the Outlines,
also a layer just for Centerlines,
and one just for Hidden lines.
Now you can draw your Roof on a Layer called "Roof" and you can use for all the different Lines the predefined Layers "Outline", "Centerline", "Hidden lines".
If you are now in need to make your Roof invisible - just switch the Layer "Roof" to invisible. You are not in need to switch all ("Outline", "Centerline", "Hidden lines") used layer separately invisible. Everything what belongs to "Roof" will be invisible.

I think that is what I meant.

Husky wrote:
terrytmp wrote:PS, "duplicate block" would be useful.
Use your already existing Block as basis - insert this block in your drawing - explode this block - change this Ex-block as you need it - save it as a new Block - done :wink:

Ok, I have found that, but usually I find I need to move the block into an area clear of other lines and detail as otherwise its easy to become uncertain of which lines belong where and theres a danger of making mistakes. As I'm usually working with the block list anyway, I would find it more efficient to duplicate the block and then edit it in block-mode where I can be certain I am only editing the block. For instance, a block might contain lines which sit directly on top of (out)lines from some other block.
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Re: Using blocks and layers

Postby Clive » Thu Jan 16, 2014 1:39 pm

Hi Terry
Try this method.

1. Here you can see lots of the same blocks in congestion, all theses blocks are named 'Block One'.

All same blocks in congestion.png
All same blocks in congestion.png (7.92 KiB) Viewed 1338 times


2. In the Block list select the option to 'Add Empty Block (BA).
3. Name the Block -i.e. 'Block Two'.
4. Select the block you wish to modify from the block list - in my case 'Block One' and click on Insert Block.
5. Next, double click on 'Block Two' in the block list to take you to this new blocks owns space. Insert your chosen block (Block One) and position it on the origin 0,0 (Red Cross).
6. Select and explode the block and change things as you wish (Line Colour, Line Type etc...).

Modified Block.png
Modified Block.png (1.76 KiB) Viewed 1338 times


7. In Block List - double click Model Space to return to main drawing area.
8. Select 'Block Two' from the block list and insert...should work okay now.

Block Two in action.png
Block Two in action.png (9.87 KiB) Viewed 1338 times
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