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For mothers day I wanted to create something very unique for my wife.  So going along with the same idea as my previous instructable Generate-a-unique-shadow-casting-sculpture, I decided to make something a little less tangible, but even more intimate.

This personalized candle holder displays a silhouette of my family on the wall and some text on a table using only the light from a little tiny votive candle.  If done correctly, the shadow will be indifferent to the specific height of the wick and flame (within the typical sizes for votive candles that is).

Instead of hanging a photo with nails, or a mural with wallpaper/paint, the candle holder...and thus the shadow, can be swapped out easily for different occasions, even during the daytime hours!


Suggestions:
Free Software:
Picasa
Autodesk 123D and Catch
Requirements:
3D printing service
 
 
Please note that the 3D printing is essential, because no other practical solution exists for creating such a structure. NONE!
Also note that I rely heavily on annotating my images in this instructable since the easiest way to see what I’m doing is with a screen capture (Shift-Command-3), upload, and click for an instant note.  Except for a few rarities, every image is tagged somewhere, so if you see a blank one, look for a itsy square crammed at the top of the image.  Sometimes, I see this happening on both mine and other’s ‘ibles and I don’t know why.  Clicking on the next image and then going back sometimes repairs the problem.

My system:
MacBook Pro
Parallels 7 running Windows 8 (AutoDesk is working on a Mac Version of 123D, but not yet out)
 
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Step 1: Decide on an environment for your shadow

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Most shadows have a common feature in that they all consist of an outline that's darkened in the middle.  With reflection, multiple or broad light sources, soft edges, or translucent materials, other effects can occur, but for this project we will consider only a well defined shadow shape and an opaque blocking material.

The lighting and environment all need to be thought through and will determine the form of shadows that you can create.

You are not limited to a single surface. Actually, you can project a shadow through multiple rooms in your house that only makes sense from one perspective if you like (example: http://www.archivenue.com/wp-content/uploads/Geometric-Illusionary-Perspective-Paintings-1.jpg).  Cast it on the ceiling, or both the table and wall simultaneously as I did.

Consider permanent obstacles, such as the chair in my photo...or dynamic ones, such as a person if they happen to sit in said chair.

Step 2: Design your scene

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The most practical tool for starting these kinds of modeling endeavors, is with some real world landmarks so you can navigating through the virtual model as you create it while having something tangible as reference.  Physical numbers used in scaling objects is necessary, but having a identifiable object in your scene makes things so much easier.

I used 123D Catch for this.  Application notes:
  1. Watch out for shiny objects, like the metal container of a votive candle, or the reflective surface of a polished table.
  2. Make sure your scene has lots of detail.  I had to reduce the detail because of the shiny table, but added written text in hopes of making up the difference.  The white spots are holes in the resulting mesh, because the software didn’t know what to do with it.
  3. Take shots from all angles to minimize vacancies in your mesh.
  4. Keep only the important things in your scene.  You may want or need to import the entire room, just crop away the rest.
  5. Export the file as an .obj

Step 3: Detail the shadow drawing

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Since mother's day was approaching, a likely subject was a family portrait.  Easy enough choice, but to make my sketching a bit easier, I first used Picasa to bring about more contrast for my shadow edges.

Also, the objective is to bring out recognizable features in binary (shaded or unshaded), that are normally easily discernible in color.  By post processing your images, it's easier to see what is important to trace, and what can be left out.

The order I used:
  1. Pencil Sketch
  2. Maximized shadows under Tuning
  3. Boost
  4. exported as a .PNG
  5. imported onto a canvas in 123D

Step 4: Fix your model's coordinate system

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Create a new 123D file by opening the .obj scene created earlier in Catch if you performed that step.  If the mesh was not scaled already in Catch, you need to do that at this step.  I knew that my final solid should be under 3x3x3 inches, and my votive candle has a diameter of 1.5 inches, so I drew a three inch square and 1.5 inch inscribed circle and then scaled the candle to fit the circle.  I also knew the height of the wick as a backup.  It is best to scale it in Catch first though.  They have videos on how to do that here.

You may adapt this whole instructable to suit your project, but I reference the base of the candle axis as my 0,0,0 point.

Step 5: Create a canvas for sketching

Construction of work axes and planes are your best friend for this project.  Understanding how the various options can clarify your virtual environment will make your experience less frustrating.  I used an offset plane to place my canvas on.  For the portrait, I wanted to cast the shadow on my wall, so I needed a plane parallel to the xz plane and 70 inches away.  I turned off the visibility of every other component in 123D and then placed my canvas using the .png image created with Picasa.


Step 6: Work the Working Axes

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Although you CAN loft from a feature to a point, I always had bad experiences with it.  Some of the steps later described here are a result of trying to fix a point lofting error.

So, the safest way for more complicate shadows involves creating a work axis connecting a point light source to a distinctive point in your sketch.  I use at least four: bottom corners, apex, and some other feature, like an earlobe.  These will allow you to copy your portrait sketch, shrink the copy and position it along the optical axis perfectly.  The work axes should go though the identical points on your copy as on your original.  Nudge the copy until it does.  Make sure you rotate around and the work axes still go though the correct points.

The copy must lie within the part that will create the shadow!
I believe that I eventually scaled my copy to 0.1 or .06 of the original.

Step 7: Add Any Additional Shadows

Text seemed like a cool idea, but it didn't go as smoothly as I dreamed.  As of this writing, 123D scales text not by points or pixels, but by whatever units you are working in.  So, naturally, I picked my font with a scaling of 8.....inches! Ah!

With eight as the lowest value that I could choose, the letter "H" in Happy Mother's Day was already twice larger than the entire sculpture.  I wouldn't be able to fit "Happy" on my dinning room table.  So I conceded to sketch the best I could the words I wanted to display.  They also aren't floating, but grounded to the candle holder.  This means that the shadow traces back to the base of the candle piece.  Floating is more challenging because your support material will create a shadow.  It must be included, and I didn't want to work that out at this point.

Use work axes the same way to position a copy of the text for tracing the projection backwards to the candle flame.

Step 8: Loft, Loft, Loft

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This would be the end if the Loft function didn't exist.  What a sad world it would be.  Lofting provides a means of  creating surfaces and solids with complicated features or transitions using only boundary profiles.  In this case we use the original and copied sketch as the profiles. Make sure you do not rotate the copied profile in any way prior to lofting.

  1. Select Create->Loft, or right click->Solid Features-> Loft
  2. Select the intended shadow surface as profile 1
  3. Select the copied surface as profile 2.  Use the swap option using the orange star icon if it shows centerline instead of profile.
  4. Chose New Component instead of Join
  5. Press Enter, or right click->OK
     

Step 9: Frame the Candle Holder

Although I show pieces of the solid at various previous steps, I haven't described how to construct the actual printable candle base yet.
  1. I started with a flat square base 3X3 inches, then extruded it 1/8".
  2. Inscribed a 1.5" diameter circle and sank it 1/16” for the candle to set in.
  3. Sketched a 1/32” radius circle onto the top surface of the base and extruded a cylinder up to 3”.
  4. Made arrays and randomish replicas of this cylinder until the entire top surface was covered. Enough posts to block all light leaving radially from the candle at the center.
    • Avoid Parent/Daughter dependencies if multiple independent patterns are made
    • Choose for each case whether the patterned components should be new components or joined.  Joining reduces further editing freedom, while a long list of independent components accompanies headaches when your processor slows down.  (whether visible or hidden)

Step 10: Finalize the Full Shadow Volume

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Riddle #1: Does a shadow have a volume?
Riddle #2: Does the light have a volume?
Riddle #3: Could you subtract one to get the other?


Up to this point, I haven’t explained how the lofts modify the scatter of posts that will ultimately create the desired shadow. The sequence:
Create->Combine->Select Single body->Select Multiple Bodies->choose Intersect->press Enter
will remove all of the material except where the multiple bodies overlap with the single body .  So you select the Solid candle holder as the single body and then all of the lofts as the multiple bodies part.  The problem is quickly evident if you only select the lofts for your multiple bodies portion.  You will retain the light blocking posts, but without a base to support them!

The different loft segment faces are separately selectable, just as in the first above image in this step.  You can “fill out” the remaining volume between the lofts by extruding these faces some exaggerated distance.  The overlap is important, not how far beyond its extended.  If you understand the rational behind what the lofts are for, and why we can use them (for angles, not absolute scale), then you will easily see that an extension in the right direction will have no negative impact on the final product.

Again, for additional explanations, review the uploaded images with notes.

Step 11: Connect Disconnected Pieces

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The unfortunate part of my construction choice is that while I wanted the final product to be abstract enough to prevent guessing the shadow, by using posts instead of a solid block of material, I leave a few danglers after the Intersection function is executed.  This is because horizontal holes larger than the diameter of a post will sever the upper portion of the post from the base.  You could print it this way, but after washing away the support material, you would be left with a tray full of “broken” pieces.  Not good.  Here was my approach:

If you made vertical posts like I did, then think vertically, 'what posts are affected with an horizontal cut?’  Then,
  • Sketch a path that connects all the affected posts with nearby unaffected ones.
  • offset the path using Sketch->Offset
  • close the path by drawing lines at the ends
  • loft to a point or a copy to ensure all of the affected posts from front to back are secured
  • Combine->Join
  • Push/Pull the end faces to meet up with the innermost and outermost posts
  • Stare at your masterwork for at least a minute with watery eyes if thats an option
I doubled up the support so that each post is connected at two points.  It just seemed like a good idea.

Step 12: Command P

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Although it shouldn’t be necessary at this point, you must ensure that all of the items that you want printed are combined into a single piece. This is accomplished as before with the Combine->Join function.

Export your file as a .stl
Currently, in 123D, you must first sign in with a username and password to enable all of the Save As options.

Now you are ready to print.  Several 3D printing services are available online, or if you are lucky to have access to your own printer, you could print out several versions of your own Super Personalized Candle Holder or make them for others.

Thanks for your comments on this Instructable’s clarity and room for improvement.
I will upload an image of the actual shadow as soon as one is available.  The speedy draft print didn’t include the internal cuts that require higher resolution. 
hkhizer2 years ago
great work, but it would be more credible if you show the effect
hendersonjase (author)  hkhizer2 years ago
Agreed hkhizer. I would if I could. That would require reprinting as the model never made it in one piece. I moved on...sadly. "Someday" I will have another one printed, but I'm too distracted
Wont the candle melt the 3D print??
hendersonjase (author)  NanoRobotGeek2 years ago
nope. I had no problems with melting.
hendersonjase (author)  NanoRobotGeek3 years ago
Of course you could have a design that is too close or too thick and the print will melt. Although I STILL haven’t see this up close, my print was made of plastic and thus could melt, but my design intent was to avoid that.

I could explain away this issue with candle convection transport, effective surface area to volume ratios, or emissivity of the plastic, but thats just silly when I can say one way or the other when it gets here. -Jason

Laminarin3 years ago
It seems like the width of your light source and its proximity to the light blocking elements would make for a very fuzzy edge on the projected shadow. Something closer to a point source seems like it would yield a crisper shadow. Maybe an led?
hendersonjase (author)  Laminarin2 years ago
A point source is ideal, but not necessary. IF the light blocking element was thin, then yes you are right, but they are multiple redundant elements. Its the same as using two almost closed irises for laser alignment or long shafts for picking out a single star only every thousand years or so.

What was shipped to me was ineffective because of improper packaging (1/4 of the posts were broken), incomplete cleaning (support material was still surrounding many of the posts), and poor printing (in both resolution and the fact that the posts were curved!).

My busy work life has hindered having alternative high-end printing services from attempting better.
melinkaya3 years ago
Is it necessary to brace the posts if the posts are shaped differently? LIke in loops or something...

And wouldn’t it be easier if the candle was taller shining down on the table?
hendersonjase (author)  melinkaya3 years ago
So a solid chunk of material thats cut minimally will certainly provide the most support and create the sharpest possible shadow. Flickering or movement of the light source will not affect the silhouette, but its not as interesting.

I actually attempted individually curved features at first, but wanted to explore arrays and didn’t consider patterns of hoops. I like that thought.

For your second question: Sharper angles are better and a taller candle would provide that when projecting on the table. However, I was concerned about the candle shrinking so significantly that I would loose the light contrast completely. Votives were simpler for me, thats all...and cheap.
lug big lug3 years ago
Why are there no pics of results? I would really like to see this thing in action!!!
hendersonjase (author)  lug big lug3 years ago
I know I know! I still don’t have it in my hands...
I hear you. I has been clearly printed, but I’m awaiting delivery. They had to make several attempts because of technical problems on their end. They took a picture of it before placing it in the mail so that I would at least have SOMETHING to show. Thanks for your interest
Well 3d printers are a pain sometimes... Ill be keeping an eye out for the pics!!!
Orngrimm3 years ago
Nice idea! :)
Is there an actual picture of the stand in use and throwing a shadow?
hendersonjase (author)  Orngrimm3 years ago
Not yet; the guys at the print shop had to take the photos in step 12. The final version is still being shipped to me.