Updated 10 Aug 2003

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Backgrounds

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Rhino can place a bitmap image into each view of your model project. This can be used as a guide for constructing the lines, surfaces and solids that make up your model. It is important that these various images are scaled to match each other, and located in space so they all line up. Usually 3 views, one from above, one from a side and one from the front are used, together with a perspective view of the model. Our bitmap images will be placed on the x, y and z axes, with the centre lines lined up with the axes. Imagine 3 pieces of cardboard slotted together, each with one of our images printed on it.

Demo of location of background bitmap images relative to model space.
Paint Shop Pro used to scan master image from printed drawing.

1.   Printed scale plans should be scanned carefully to get a clean image, and make sure it is level so the centre lines are horizontal or vertical. If not, move the paper and re-scan. Don’t use any ‘Rotate’ or ‘De-skew’ function in your Paint program, it will distort the image. Save the master image of the drawings, then make selections from this for each view that you need. Here the front view has been selected and saved as a seperate image.

2.   Load the seperated images back into your paint program and change the background colour to a light grey, the black lines to white. This will make them much easier to trace over when placed in the Rhino views. Rhino can handle jpeg, bmp, tiff, png and pcx image formats as backgrounds. You will need a plan, right side and front view if you use the conventional Rhino layout. This might mean flipping some images if the original drawing had only a left view. Make sure you know about any asymetric features such as intakes, hatches, and check they are placed on the correct side of your model. 

Paint Shop Pro, changing scanned images from black and white to white and grey.

3.   The plan view will have to be rotated 90 degrees so the nose of the aircraft points up the screen of your monitor. This is to match the co-ordinate system of the views in Rhino. This is the only time the image can safely be rotated in software. Sometimes plan views on drawings are rotated simply to get the image onto the printed page. In this case you will have to twist the pages on your scanner to compensate.

Rhino Front view, wingspan marker and Background Bitmap selection dialog box.

4.   In Rhino, select the front view and draw a short vertical line half the aircraft wingspan from the 0,0 point (where the red and green lines touch) Here I have dimensioned the distance to check; the MB5 wingspan is 35ft  0 inches.

Rhino Background Bitmap button and toolbar showing additional controls.

5.   Click the Background Bitmap button to select the image for the front view, click once in the view, drag and click again and the bitmap will be placed into the view. Then click on the ‘Move Background Bitmap’ button, zoom in on the prop spinner and click once on the centre, then type in 0,0 (enter) . The bitmap will move so the point just clicked will be at the 0,0 point, ie where the red and green marker lines join.

Rhino Front view, Front view bitmap initial placing before aligning and scaling.
Rhino Front view, Front view bitmap aligned with 0,0 point but not yet scaled.

6.   Now we need to scale the image. Click on the ‘Scale Background Bitmap’ button, then type in 0,0 (enter) . Now zoom in on the wing tip of the bitmap and click once. Now as you move the cursor the bitmap will scale up and down, centred on the 0,0 point. With ‘End’ snap selected on the Osnap menu, move your cursor near the top end of the little vertical marker. When the cursor snaps to the marker line, click once again to finish the command. Presto! Bitmap aligned and scaled. Now repeat for the side and plan views in the other view windows, and we are nearly ready to Rhino!