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With the animated helpers in place, you are now ready to animate the ink flow.
You will use a cylinder that you deform along a path to create that effect.
Use Alt+MMB to orbit around and get a better look at the scene.
Create a cylinder anywhere. You'll be adjusting the position in a minute.
Use the F4 toggle if you need to see its underlying geometry.
In the Modify panel, apply a World Space Modifier: Path Deform (WSM) to the cylinder.
Click Pick Path and then choose the first path you want to use, namely Sig-Path-01.
The behavior may seem illogical as the cylinder jumps to an unexpected location.
This can easily be fixed by choosing the Move to Path option.
Go back to the cylinder level and adjust its radius value to simulate an ink width that makes sense.
You'll need to apply a black or a dark material to it.
Go to the Slate Material Editor and use the already supplied Standard material named Ink.
The idea now is to animate ink flow by changing the Stretch value of the Path Deform modifier.
There are two issues to solve:
One is to control the stretch using the already animated point helper,
the other is preventing the cylinder from distorting too much near the end of travel, and mostly around curves.
The second problem is easy to fix. Simply go back to the cylinder level and increase the Height Segments value.
You can set this value as far up as 200.
However, even a value as high as 200 may not be enough if the path is too long.
In such a case, you're better off breaking a path in two or more splines,
which is why you separated Sig-Path-02 from Sig-Path-03 earlier, even though they are meant to work as one pen stroke.
To animate the Stretch value to follow the point helper, you will use wiring.
When the point is at the beginning of the path (path % value of 0), the Stretch value should also be zero.
When the point is at the end of the path (Path % value 100), the Stretch value should be in this case 5.215
This value could be slightly different based on how you shaped your path earlier and the height of the cylinder you have just created.
Adjust the Stretch value visually to see what it reads as the cylinder stretches to the maximum needed point.
Make note of that value as you will need it in the wiring expression. In this movie, we'll use the value 5.215
Right-click the selected cylinder and choose Wire Parameters from the Quad menu.
Select Space Warps > Path Deform Binding > Stretch and then point and click the point helper traveling on that same path.
Choose Transform > Position > Path Constraint > Percent.
The Parameter Wiring dialog appears.
You want the helper to control ink flow, so make sure you set the direction in one way only, from the helper to the cylinder.
In wiring mode, the Percent value ranges from 0 (0% of the path) to 1 (100% of the path).
You need to multiply that path value by the maximum Stretch value of 5.215
Simply add a *5.215 to the expression so that it reads "Percent*5.215".
Click the Connect button.
Scrub the animation and notice how the animated helper drags with it the ink flow, based on the deformed cylinder.
Repeat the procedure for the second and third paths.
Create cylinders with the same radius value you used before,
make sure they have enough height segments,
and bind them to their respective paths using the Path Deform (WSM) modifier.
Always remember to use the Move to Path button to relocate the cylinders properly.
Verify the maximum Stretch value you need for each cylinder.
In this movie we're using 9.073,
and 18.765 respectively.
Apply the Ink material to both objects.
Once this is done, you can then wire each cylinder to its appropriate helper,
multiplying the percent value by the appropriate amount you identified a few moments ago.
You're fairly done with Ink flow.
If you look closely though, you will see three small disks at the base of the paths before each stroke is made.
Even with a Stretch value of 0, the circular base of each cylinder is still visible.
To prevent that from happening, you can animate the radius of the cylinder to go from 0 to its "normal" value, just as the helper starts moving.
In the case of the first ink stroke, set the radius to 0 and go to frame 61.
If you recall, the helper for that ink stroke starts moving at frame 60.
Enable Auto Key and set the radius to what it was a moment ago, in this movie it was set at 0.4
This animates the radius between frames 0 and 61, but you need it animated between frames 60 and 61.
Simply move keyframe 0 to the 60 position.
Repeat the procedure for the second ink stroke to animate its radius between frames 130 and 131,
and also for the third ink stroke to animate its radius between frames 220 and 221.
This covers the animation of the ink strokes.
In the next and final movie, you animate the pen to follow the three separate helpers over time.