Software Knowledge Base

Note ID: 000087 – Applications: SLABS4

Title: SLABS4 manual – Modelling - Example 2: Simple flat plate – Bitmap import (used as a background only)

Description: General overview on how to generate a model using a Bitmap image

See Also:

Date Created: 25/03/2008

Date Modified: 25/03/2008

Using a bitmap image to generate a model is very efficient particularly when the geometry of the floor is simple.

The concept of the BMP Import utility in SLABS4 is to use a Bitmap image to display the geometry of the floor as a background image. Once the Bitmap image is imported, the standard drawing tools can be used to create the slab panels, walls, beams and columns over the Bitmap image. The Bitmap image is only a background and it will not interfere with the slab model. A Bitmap image can be created by scanning a paper copy of the plan (using a scanning device), or the image can be created from a CAD file using any CAD package.

Creating a bitmap image (using a CAD file) is outlined below;

1. Start AutoCAD.

2. Open the architectural drawing.

3. Change the colour of the background to White.

4. Press the [Alt] + [Print Screen] keys on the keyboard. This will save the image of the screen to the clipboard.

5. Close the CAD package.

6. Start MS Paint or an alternate photo / image editor.

7. Press the [Ctrl] + [v] buttons on the keyboard. This will paste the image form the clipboard.

8. Save the file to any directory on the hard drive. Note: the format of the file must be set to ‘16 Colour Bitmap’ in order to reduce the size of the file.

Note: Creating Bitmaps using AutoCAD [ File > Export > bmp format ] is not a suitable method of creating Bitmap files for importing into SLABS4.

The following example is a step by step procedure that includes detailed key strokes and specific commands entered by the user.

Below is a CAD drawing in AutoCAD where: the supporting square columns displayed in blue, the perimeter of the slab is magenta and the step in the soffit (beam outlines) are displayed in black.

Sample Screen Shot – Example CAD file in AutoCAD

Holding the [Alt] key down and pressing [print screen] on the keyboard will save an image of the screen to the clipboard. Pasting the image to MS Paint is performed by holding the [Ctrl] key down and pressing the [v] key. The image needs to be cropped to remove the unnecessary areas of the screen, as shown in the screen shot below;

Sample Screen Shot – Cropped Bitmap image in MS Paint

The file is then saved as a 16 bit bmp image and is ready to be imported.

To import the Bitmap image the user needs to select [ Tools > Bitmap > Import ] from the Main Menu. SLABS4 will launch a window and the user needs to locate (and open) the Bitmap file using this window. The screen show below shows the bitmap file displayed as a background image within the Working Area.

Sample Screen Shot – Bitmap image displayed as a background

The next step is to scale the image by selecting [ Tools > Bitmap > Scale ] from the Main Menu. SLABS4 will then prompt the user to click on two points (horizontal or vertical on screen) and enter the actual distance measured in AutoCAD. In order to make the scaling as accurate as possible, the user should try and click between two points that represent the largest dimension on the bitmap. In this example, this would be the vertical distance between grid lines ‘A’ and ‘D’. The distance measured in AutoCAD is ’24.2m’ and this value needs to be entered into the input box, as shown below;

Sample Screen Shot – Bitmap scaling: Input box

Once the bitmap has been scaled the elements (slab, column, beam and wall) are generated using the tool box. It is recommended to use a 1.0 m x 1.0 m major grid, and a minor grid of 1/5 or 1/10.

Notes on BMP Import

· The location of the bitmap within the Working Area can be shifted by holding down the [Ctrl] button and using the arrow buttons on the keyboard.

· The ‘PageUp’ and ‘Page Down’ can be used to scale the image by incremental steps.

· After the import and scaling are performed the Bitmap should be ‘locked’ so it is not accidently shifted or scaled.

· The Bitmap image can be switched Off and On at any time, and can be unloaded from the model at any time by selecting the [ Tools > Bitmap > Unload ]. Once the image is unloaded a new Bitmap image can be loaded in the same SLABS4 model.

· It is recommended to keep a backup copy of the Bitmap, so it can be loaded again at any time.

Bitmap On/Off Switch