Bitmapping a lathed cylinder

This tutorial describes the process of wrapping a bitmap material around the outside of a cylindrical lathed object. This, much like extrusions, tends to give some Swifters a lot of grief trying to line the image up correctly. The most common use for this would be to bring realism and life to such things as bottles, cans and basically any tubing/cylindrical shape that requires a full graphic coating. For this tutorial we will concentrate on the soft drink can.

So how do we do it?



 Step 1 - Creating the object
 

Creating the object is very simple. To create the cylinder we only need to draw a profile of half of the can in the lathe editor.
Work in either the top or bottom quadrant as this will affect the material location when we apply the bitmap material later on.
The sweep angle is set at 360º, smoothing is on and if you want a high end finish, set the segments to 64.



 

By jumping between the lathe and main editors you can refine your bezier points of the lathe until you are satisfied you have a well proportioned object.



 Step 2 - The bitmap
 

When using a bitmap it is important to note that the program squares up your image.
e.g. - A 200x100px image will become 200x200px. That isn't the actual size it becomes, I am merely trying to convey that the image becomes a square shape. I have supplied the bitmap I used so you can continue the tutorial without scouring the web for a decent image.

The image on the left is 512x502 px in size and can be downloaded here.



 Step 3 - Creating the material
 

Go to - Setup > Materials. Highlight "Bitmap" from the list and select "Add Material...". Give your new bitmap texture a Name (e.g. 'diet coke' ). In the Finish sub-panel, open the Ambient Color picker - select white. In the Color sub-panel, select "Bitmap Image" from the Pattern drop down menu. When prompted to select a file - select the diet_coke_material.bmp file. Select "Cylinder" from the Wrap drop down menu. Check the Scale box. Leave all other settings at their default values! Hit "OK" and "Done" respectively. You can view the full panel image with all settings required Material Panel.



 Step 4 - Applying and aligning the material
 

To understand the way bitmaps are wrapped around the surface of a lathe, I have put together a demonstration as shown on the left, of where the bitmaps are positioned within the lathe editor. As you can see - each quadrant has it's own image and it always starts at absolute centre. That's 0,0 position co-ordinates.



 
From these positions the program starts to wrap around the lathe object. I have created 4 lathed objects with sweep angles of 180º, 270º, 320º and 360º. See how each time they start from the centre and wrap out along the lathe. Now the most important thing to remember in this tutorial and what you are looking at in the left image is this: The manual says the default setting for the scale of the bitmap material is 1:1. This is not quite correct. It is off a bit. By selecting the Scale radio box when creating your material it scales it to 1:1. Do not adjust the slider. This is where all the problems stem from when trying to wrap. So now it will make the bitmap start at the beginning of the sweep and end at exactly 360º. A perfect fit.


 

As proof, the two lathed objects on the left are identical. I then created and placed a material on the left one which has the Scale radio box selected. The other one has a copy of the same bitmap material but with the Scale radio box deselected. Does the latter image looks familiar when you tried to wrap?



 
To continue, you simply apply (drag and drop) your newly created bitmap material to the lathed object and it will fit. If the image carries on past the bottom or top of the object - go back to the lathe editor and grab the bottom/top of the lathed object and drag it up or down to bring it back in line with the bitmap material now that you know where it is sitting in the lathe editor window. Use the height scale to bring the object back into proportion if needed.


 Step 5 - Completing the scene
 

For my demonstration I moved the lights around and darkened them slightly to reduce the glare coming off the objects. The whiteboard marker was created in the exact same way the can was. The table is just a round cornered extrusion with a wood grain material applied. The background is another extrusion with an image of some chairs on it.