Hi everyone, I'm Yunyi Zhu from MIT.
I'm Jiani Zeng, also from MIT.
Today, we will introduce lenticular objects,
which are 3D printed objects with lenticular lens surfaces
that can change their appearance depending on the viewpoint.
Many of you might have seen
this type of lenticular cards before.
They allow people to see different image patterns
from different viewpoints,
and they are widely used in arts and advertisement.
For example, this gift card that displays a small tree
from a lower viewpoint and a larger tree from a higher one.
And we were wondering if we could apply a similar effect
to the surfaces of 3D objects,
so that not only 2D cards, but also 3D objects can reveal
different patterns from multiple viewpoints.
First, let's see how lenticular effect works on traditional 2D
cards with flat surfaces.
Those cards or surfaces are normally covered with tiny
lenses like this one.
Each lens has an underlying color pattern.
For example, this particular lens has a red dot on the left side
and a blue dot on the right side.
If an observer looks at the lens from its left,
the shooting rays out of his or her eyes will be refracted
onto the blue dot
so that the entire lens will show up as blue.
If this person moves to the other side, the rays will
instead be directed to the red dot.
In this case, the entire lens will show up as red.
This is how one lens reveals two different colors
under two viewpoints
Together, all the lenses with different underlying colors or
patterns can create lenticular effects like this one here.
In our research, we applied the similar concept to 3D objects,
such as this AirPods case with pattern shifting effects,
and this kettlebell shell that helps to correct users' body
pose during exercise.
It shows an upward arrow when the users arms are too low and
a downwards arrow when they are too high.
The users will only see the check mark when they lift the
kettlebell to the recommended height.
Our system has two contributions.
First, A 3D editor that allows the designer to generate files
for lenticular objects.
And second, a fabrication pipeline that effectively
fabricates such objects.
I will demonstrate them with the kettlebell shell example
that we've just looked at.
To make this kettlebell shell, I first import
the shell object from the files.
I then set up a viewpoint,
and I move it to the correct location
in the viewport on the right.
At this viewpoint, the kettlebell is at the correct height,
so I assign it the checkmark image.
Now that I have set up all three viewpoints, I can then
preview the appearances from different angles.
The lenses and color pattern are then generated automatically.
So I just showed you the editor for creating the lenses and
color pattern.
Now let me talk more about the fabrication pipeline.
After making the 3D models,
users can fabricate their objects.
In the case of the kettlebell shell example that I've just created,
I first use a renderer to preview the
lenticular effects.
I then 3D print the object, the lenses and the color pattern,
all in one pass.
After that, I coat the 3D printed lenticular object with
three layers varnish.
And here's the result.
Upwards arrow,
the downwards arrow,
and the checkmark.
So before I dive in more to the fabrication parameters, let me
briefly zoom out and talk about the lens geometry.
To prepare for the best final result, we need to
balance two factors.
First, we need to minimize the height of each lens.
If a lens is too tall, it will stick out too much
from the original object.
And second, we need to maximize the number of viewpoints that
each lens can support.
To find a good balance between the two factors,
we've calculated how different lens parameters affect the size
of the largest image spot, which is inversely related to
the number of viewpoints.
We then plotted the relation between the image spot size and
the lenses base height.
And we then selected the point marked in the plot,
which gives us both small lens height and
a large number of viewpoints.
If you are interested in more detail on the lens geometry
recalculation, please check our paper
As a result, our selected lunch geometry supports 19 viewpoints.
Here, we back it up with the rendered image of the same lens
showing 19 different colors.
This, however, is a theoretical value, and it assumes that the
lenses are fabricated perfectly.
In fact, the fabrication technique still has limitations,
and the lenses we fabricate typically don't have such
perfect surfaces.
Therefore, our next step is to find the smallest lens size
that we can realistically fabricate.
We first tested the printable resolution of the underlying
color pattern,
and we then tested various lens sizes and post processing
methods to make sure the surface quality of the lens is
acceptable.
According to our results, we recommend using lenses with
three millimeter diameter, and post process it with art varnish.
Showing here are the best result we can currently achieve.
We can see that the best fabricated results are still
not coming close to the image quality of the rendered result.
And thus we conclude that the fabrication is still a big
limitation, which might cause the fabricated objects to look
different from the simulation.
For some more use cases we fabricated this nightstand that
dynamically creates the user.
For example, when I'm in bed, I have a lower viewpoint, and
it will show me "Good Night".
And when I sit up, now I have a higher viewpoint, and
it will show me "Good Day".
Another use case involves a pair of shoes that can
cheer me up.
When I'm having a bad day, I wear these shoes, look down and
see a "Cheer Up" message.
But this message is secret, because when other people look
at my shoe, they look at it from the side, which only shows
a standard shoe design.
Our work is part of the larger vision of making objects with
dynamic appearance.
Prior works have used smart materials and integrated LEDs
to achieve such goal,
while our approach uses lenticular lenses to create
different appearances from different viewpoints.
In the future, we aim to find more approaches
towards this vision.
And for this particular approach, we plan to support
dynamic lens geometries, so that we have smaller lens
heights and better viewing range.
Thank you very much for listening to our talk and
I'm happy to take any questions.