All of the Points Generate commands assume that a CAD file has been imported into the project, and then backclothed with a normal model which is where the new points will be stored after they are generated.
A quick way to generate the model is to right-click on the CAD file and then select Backcloth Create.
Following this, you will be asked to enter a name for your file. Enter a suitable name and then press OK.
When generating Points from most CAD elements a dialog similar to that below will be displayed.
The first column identifies how the height of the new points will be calculated. The options are...
- Assigned: Uses the existing levels of the CAD detail, so this assumes the CAD is also 3D.
- Null: Sets the level of the points to Null.
- Datum Height: Sets the level of the points to a preset height.
- Model Interpolation: Allows the new points to be heighted by interpolating onto a selected DTM or Point Cloud. If selected, the Reference Model box becomes active so that the appropriate surface can be selected.
- Above Model: Similar to the option above, but allows for a fixed offset to also be applied.
- Text Value: This option is used for giving heights to closed lines such as slabs. It assumes the text is an actual height.
- Extract from Text: This is similar to the above option, but will go searching for a numeric value in the text, rather than assuming it is an actual text value. i.e. FFL:20.345.
- Model Trend: This allows the new points to be interpolated to a trend surface generated via the DTM Trend tool.
- Closest Text: This option can be used for 2D detail and searches for CAD text in the vicinity of the new point. If you select this option then the Max Text Offset box becomes active so that a limit can be placed on how far n4ce should go looking for the closest text. Otherwise, it's possible for it to use a completely unrelated piece of text.
- Existing Points: This allows Point elements that are not part of the line, but which have a 3D level, to be used instead of the node on the existing polyline.
The Parameters panel allows the setting of a Code and String Numbers are allocated. The Options panel provide further choices, including checking for duplicates and taking the code from the layer name. Other non-applicable options are greyed out here.
- Layer is a Code: This is where the CAD folder is structured so layer names are the feature code of detail stored on that layer.
- Prefix Created Points: Will add a G to the point number of points created.
- Check Duplicates: Removed any points that are duplicated.
- Filter Along Lines: This option will both smooth out features and remove redundant points along lines, using an algorithm called Douglas Peucker. It works by calculating the offset of the middle of three points and comparing this to the Filter Offset.
- Trace Lines: Can be used to link individual line segments to make continuous features.
- Trace Tolerance: Allows the ‘touching’ tolerance to be set for segmented lines.
- First Point Only: Identified the first point on a line feature. Remember lines are directional.
- Midpoints Only: Finds the midpoint of segments. Levels are linearly interpolated between endpoints.
- Inside Lines Only: Used for generating points for house slabs where the level of the strings are inside each slab.
- Add Point to List: Adds the new points to the Select List.
- Circumferences: When generating points from ARCs or CIRCLES, this sets the points to be generated around the circumference at regular intervals dictated by the Maximum Spacing box.
- Centers: When generating points from ARCs or CIRCLES, this sets the points to be generated to be at the Centers.
Once this has been selected a new window will appear with which we can configure our mode of extraction.
Methods for controlling the Heights are as follows.
- If you choose Typed, you will be asked to enter the Height after right-clicking.
- If you chose Indicated Text, you will be asked to indicate an item of text in the CAD model that represents the height of the indicated contours.
- Text at Ends - This option automatically picks the Height text at the end of each contour. This is very useful when selecting all of the contours at once. With this option we can also enter a Max Text Offset, this will mean n4ce will only search within the entered radius to find a value. If a height is not found the contour will not be generated.
- Strike Line - This tool will require you to strike the contour lines and input the first and last contours Heights. n4ce will then calculate the contours interval.
- Sequential - This tool just asks for the height of the first contour that has been struck, and then the interval. It will also remember the last interval it generated so that you can keep clicking and not have to input any more values unless the direction of the interval changes.
When in Sequential mode this dialog controls the tool. If Indicate Cad Heights is used, then the interval will be auto-calculated. If you are starting by striking through a contour that has already been extracted, then you can use the skip option to miss out any lines that have already been converted.
Further options to aid the generation of points from contours are...
- Indicated Heights: Allows the start and end levels for Strike and Sequential modes of the contours to be determined by clicking on an appropriate item of CAD text. In Sequential mode you only need to do this the first time the tool is used, as from then on it will calculate the interval for you.
- Filter Along Lines: Simplifies the number of points along the contours. By varying the offset value, different degrees of simplification can be achieved.
- Prefix Created Points: Adds the prefix C to the point number of any generated points.
- Add Points to List: Adds the new points to the Select List
This option differs from all the other modes because rather than tracing over elements, it actually reads the contents of a CAD table such as the one in the image below.
Having selected this tool a dialog similar to that below will pop up.
Here you can set up the order of the data that is expected in the columns. Note if no Code column is defined, then one will be asked for as part of the process.
Once the correct column order has been set up press OK, now just rectangle the table and the points will be generated and added to the model.