Working Out Dimensions From a Photo
During a recent presentation I made to a SketchUp users group, I was asked to provide some strategies for working from photos. There are a few different methods available including Match Photo. I like to use Match Photo when I can but it doesn’t work so well with images that have been cropped or those to which perspective correction has been applied. Often, even if Match Photo would work, the project is simple enough that it doesn’t warrant the setup time.
Here’s another option that I find works well and is rather fast. For this example I found an image of a chest of drawers made in Denmark in the 1930s. In this case I have the overall dimensions of the piece and I can approximate some of the dimensions but I’d like to know the height of the drawers and the base.
The first step is to import the image into SketchUp. Use File>Import and make sure you choose Use as image. Setting the view to the standard front view first will make it easier to get things set up. After choosing the image, click on the origin and drag up and to the right. The size of the image isn’t important at this point. It’ll get fixed in the next step, though.
Choose the line in the piece you’ll work off of. In this case the near front corner will work fine. Using the Tape Measure tool, place horizontal guidelines at the bottom and top corners. Draw a vertical line between those two guidelines, shown selected, above. Then use the Tape measure tool to measure the line making sure you click on both endpoints. The measured distance will be shown next to the cursor and also in the Measurements window.
Without clicking anywhere else or moving the mouse type the actual dimension and hit Enter. A message window will pop up asking if you wish to resize the model. Choose Yes and then click on Zoom Extents so you can see the entire image again.
Now, you can set out some guidelines to identify the points you need. It might take a little eye balling to get those guidelines where they need to be but you should be able to get close. For this piece, with the drawer offset a little from the line I measured, I had to adjust the guidelines and mentally extend lines in the image out to the corner. That’s not nearly as difficult as it might sound, though.
Since this piece was made in Denmark, I am fairly sure it was built in metric units but the overall dimensions I had were in inches so I stuck with them. I also made sure that the dimensions came out to something I could actually work with in the shop if I were going to build it.
Before starting to draw the model I added the dimensions between guidelines. Then I selected everything and move it all straight back in the green direction. This then gave me the space to draw the model and let me use the image for reference. When you move the image back, move it far enough away so it isn’t in your way but keep it close enough so you don’t have to zoom in on it much as you’re working.
When I got to the point where I no longer needed the image, I deleted it and the dimensions from the model space. Then I finished up the model.
This process of working from an image can be useful if you want to create reproductions of existing pieces or you could use the model you create from the image as a starting point for a different piece. Once you have the model at least started, you can modify it as needed to suit the purpose. Starting from an image of an existing piece of furniture can save you some work figuring out all of the dimensions. Drawing existing pieces of furniture is also a great way to get some practice using SketchUp.
I think this is a useful method to keep in your bag of tricks so give it a try when you get a chance.