Following a Spline

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* {{l|Doc:Following a Spline#Create the Layers|Draw a curve and an arrow}}
 
* {{l|Doc:Following a Spline#Create the Layers|Draw a curve and an arrow}}
* {{l|Doc:Following a Spline#Make the Arrow Move and Rotate|Link the arrow's Origin and Rotation}} to the Spline so the arrow follows the curve
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* {{l|Doc:Following a Spline#Make the Arrow Move and Rotate|Link the arrow's Origin and Rotation}} to the Spline so that the arrow follows the curve
  
 
== Tutorial ==
 
== Tutorial ==
  
This is a brief tutorial giving an example of how to use it:
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The tutorial is intended to provide a demonstration on how to use this feature.
 +
 
  
 
=== Create the Animation ===
 
=== Create the Animation ===
  
File > New
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* Create a new animation by selecting from the menu {{c|File|New}}.
 +
 
  
 
=== Create the Layers ===
 
=== Create the Layers ===
  
Select the {{l|Spline Tool}}
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First step, let's draw the Spline:
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* Select the {{l|Spline Tool}} from the Toolbox:
 
[[File:Spline-tool-0.63.06.png|frame|none]]
 
[[File:Spline-tool-0.63.06.png|frame|none]]
  
enable just the Outline checkbox
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* In the {{l|Tool_Options_Panel}}, enable only the Outline Layer type.
  
draw a spline that you want the arrow to move along
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* Draw a Spline that you want the arrow to move along.
  
click the {{Literal|Make Spline}} icon in the bottom left of the {{l|Tool_Options_Panel}} to create the spline.
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* Click the {{Literal|Make Spline}} icon in the bottom left of the {{l|Tool_Options_Panel}} to create the Spline.
  
still in the Spline Tool, enable {{Literal|Create Outline}} and {{Literal|Create Region}} checkboxes in tool options
 
[[File:Spline-Tool-Options_0.63.06.png|frame|center]]
 
  
draw an arrow or whatever, pointing to the right.
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Second step, let's draw the arrow:
  
Switch to the {{l|Transform Tool}}
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* Select the {{l|Spline Tool}}, this time enabling {{Literal|Create Outline}} and {{Literal|Create Region}} Layer types:
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[[File:Spline-Tool-Options_0.63.06.png|frame|none]]
  
select the outline, hit control-a to select all its {{l|Handle|handles}} except the green position handle
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* Draw an arrow (or any another arbitrary shape) pointing to the right side of the Canvas.
  
drag the handle so that the arrow is centred around the green position handle
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* Switch to the {{l|Transform Tool}}.
  
Add a {{l|Rotate Layer}} above the outline and region
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* Select the Outline, press {{Shortcut|Ctrl+a}} to select all its {{l|Handle|handles}} except the green position handle.
  
{{l|Group}} the rotate, outline, and region layers
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* Drag the handles so that the arrow is centered around the green position handle.
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* Add a {{l|Rotate Layer}} above the Outline and Region Layers.
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* {{l|Group}} the Rotate, Outline, and Region Layers. At this point there are 2 top-level Layers:
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** an Outline Layer
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** a Group Layer containing the arrow and the Rotate Layer
  
so now you've got 2 top-level layers: a curved path, and a group containing an arrow and a rotate layer
 
  
 
=== Make the Arrow Move and Rotate ===
 
=== Make the Arrow Move and Rotate ===
  
* Select the group layer by clicking it in the {{l|Layers Panel}}
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* Select the Group Layer by selecting it in the {{l|Layers Panel}}.
* Select its green position {{l|Handle|handle}} by clicking on it in the {{l|WorkArea}}
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** additionally select the Rotate layer by holding Control and clicking it in the Layers panel
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** additionally select the blue "rotation amount" handle by holding {{Shortcut|ctrl}} and clicking on it in the canvas window
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So now we should have 2 layers selected, and one handle from each of those 2 layers selected
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* Then:
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** select its green origin position {{l|Handle|handle}} by clicking on it in the canvas window
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** select the Rotate Layer by holding {{Shortcut|Ctrl}} and clicking it in the Layers Panel
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** select the blue rotation handle by holding {{Shortcut|Ctrl}} and clicking on it in the canvas window
  
Now additionally select the curved spline layer (it should be the last layer in the Layer panel's list) by holding {{Shortcut|ctrl}} and clicking on it
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At this point, there are 2 Layers selected and one handle from each of those 2 Layers selected.
  
Right-click on the dotted line that indicates the position of the curved spline - not on any handle, but on the dotted line between handle
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* Now, select also the curved Spline Layer (it should be the last Layer in the Layer Panel's list) by holding {{Shortcut|Ctrl}} and clicking on it.
  
From the context menu that pops up, select {{Literal|Link to Spline}}
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* Right-click on the dotted line that indicates the position of the curved Spline, not on any handle, but on the dotted line between handles.
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* From the context menu that pops up, select {{Literal|Link to Spline}}:
 
[[Image:Spline-Link-to-0.63.06.png|none|frame|See also {{l|Command:Link_to_Spline}} ]]
 
[[Image:Spline-Link-to-0.63.06.png|none|frame|See also {{l|Command:Link_to_Spline}} ]]
  
The arrow group should move so that its green position handle is on the spline, and it should rotate so that the arrow points along the spline at that point
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The arrow Group should move so that its green position handle is on the Spline, and it should rotate so that the arrow points along the spline at that point.
  
Select just the group layer, and drag its green handle around. you'll see that the handle is constrained now to line on the spline, and that dragging it also affects the rotation of the arrow as expected
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* Select just the Group Layer, and drag its green handle around. The handle is now constrained to the Spline and dragging it will also affect the rotation of the arrow.
  
We can now animate the arrow. turn on {{l|Animate_Editing_Mode}} by clicking the icon in the bottom right of the canvas window.
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We can now animate the arrow.
  
* at time '''0f''', drag the group layer's green position handle to one end of the spline
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* Turn on {{l|Animate_Editing_Mode}} by clicking the icon in the bottom right of the canvas window:
* at time '''5s''', drag the same position handle to the other end of the spline
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** at time '''0f''', drag the Group Layer's green position handle to one end of the Spline
 +
** at time '''5s''', drag the same position handle to the other end of the Spline
  
Try {{c|<Caret Menu>|<File>|Preview|}} to watch the animation.
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Try {{c|File|Preview|}} to watch the animation.
  
 
== Results ==
 
== Results ==
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[[File:Arrow-follows-bline.gif|center|alt Following a Spline example]]
 
[[File:Arrow-follows-bline.gif|center|alt Following a Spline example]]
  
Synfig project : {{l|Media:Arrow-follows-bline.sifz‎|Arrow-follows-bline.sifz‎}}
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Synfig project: {{l|Media:Arrow-follows-bline.sifz‎|Arrow-follows-bline.sifz‎}}
  
 
== Controlling the linear velocity ==
 
== Controlling the linear velocity ==
  
By default, the arrow travels the whole spline with a constant velocity, independently of the spline structure.
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By default, the arrow travels the whole spline with a constant velocity, independently of the Spline structure.
 +
 
 +
If you select the Group Layer and look at the Parameters Panel, you'll see that its Origin parameter is {{L|convert|converted}} to {{Literal|Spline Vertex}} type. This is done automatically when {{Literal|Link to Spline}} is executed.
  
If you select the group layer and look at the Parameters Panel, then you'll see that its Origin parameter is {{L|convert|converted}} to {{Literal|Spline Vertex}} type. This is done automatically when you do "Link to Spline" action. You can disable the "Homogenous" subparameter and then the speed of the arrow will depend on the spline structure - it will take the same time to move along each segment of the spline. So if there's a long straight part then a bendy complex part, the arrow will move much faster along the straight parts (since there will be less vertices in that part). In physics terms, the linear velocity (that is, the speed over the spline) is not constant.
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You can disable the "Homogenous" subparameter and then the speed of the arrow will depend on the Spline structure, it will take the same time to move along each segment of the Spline. So if there's a long straight segment then a bendy complex part, the arrow will move much faster along the straight segments (since there will be less vertices in that part). In physics terms, the linear velocity (that is, the speed over the Spline) is not constant.
  
 
For illustration of the "Homogenous" effect see [http://www.youtube.com/watch?v=3PGXroxBcuo this demo].
 
For illustration of the "Homogenous" effect see [http://www.youtube.com/watch?v=3PGXroxBcuo this demo].
  
 
== See also ==
 
== See also ==
* Synfig forum : [http://www.synfig.org/forums/viewtopic.php?f=8&t=4563 Following a path duplicated]
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* Link to Spline command: {{l|Command:Link_to_Spline}}
* Synfig forum : [http://www.synfig.org/forums/viewtopic.php?t=2803 animate a "travel path"]
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* A [https://youtu.be/d1hPxgq2qeU video tutorial] showing the steps of this page.
* Synfig forum : [http://www.synfig.org/forums/viewtopic.php?f=8&t=9157 A path of scraps(or any other object)]
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* Link to Spline command : {{l|Command:Link_to_Spline}}
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* A [https://youtu.be/d1hPxgq2qeU video link] showing the explanation of this page.
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Revision as of 00:44, 28 March 2020

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Note: There is also a slightly out-of-date tutorial on this topic at Tracking Curves. It contains some info, particularly about link/export, which hasn't yet been added to this new tutorial. There is also another very out-of-date tutorial for synfig 0.61.08.

Introduction

This tutorial will demonstrate how to make an object follow the path of an arbitrary curve, rotating to face the direction of travel.

Summary

We're going to:

Tutorial

The tutorial is intended to provide a demonstration on how to use this feature.


Create the Animation

  • Create a new animation by selecting from the menu "File → New".


Create the Layers

First step, let's draw the Spline:

Spline-tool-0.63.06.png
  • Draw a Spline that you want the arrow to move along.
  • Click the "Make Spline" icon in the bottom left of the Tool Options Panel to create the Spline.


Second step, let's draw the arrow:

  • Select the Spline Tool, this time enabling "Create Outline" and "Create Region" Layer types:
Spline-Tool-Options 0.63.06.png
  • Draw an arrow (or any another arbitrary shape) pointing to the right side of the Canvas.
  • Select the Outline, press Ctrl+a to select all its handles except the green position handle.
  • Drag the handles so that the arrow is centered around the green position handle.
  • Group the Rotate, Outline, and Region Layers. At this point there are 2 top-level Layers:
    • an Outline Layer
    • a Group Layer containing the arrow and the Rotate Layer


Make the Arrow Move and Rotate

  • Select the Group Layer by selecting it in the Layers Panel.
  • Then:
    • select its green origin position handle by clicking on it in the canvas window
    • select the Rotate Layer by holding Ctrl and clicking it in the Layers Panel
    • select the blue rotation handle by holding Ctrl and clicking on it in the canvas window

At this point, there are 2 Layers selected and one handle from each of those 2 Layers selected.

  • Now, select also the curved Spline Layer (it should be the last Layer in the Layer Panel's list) by holding Ctrl and clicking on it.
  • Right-click on the dotted line that indicates the position of the curved Spline, not on any handle, but on the dotted line between handles.
  • From the context menu that pops up, select "Link to Spline":

The arrow Group should move so that its green position handle is on the Spline, and it should rotate so that the arrow points along the spline at that point.

  • Select just the Group Layer, and drag its green handle around. The handle is now constrained to the Spline and dragging it will also affect the rotation of the arrow.

We can now animate the arrow.

  • Turn on Animate Editing Mode by clicking the icon in the bottom right of the canvas window:
    • at time 0f, drag the Group Layer's green position handle to one end of the Spline
    • at time 5s, drag the same position handle to the other end of the Spline

Try "File → Preview" to watch the animation.

Results

This is the animation I ended up with:

alt Following a Spline example

Synfig project: Arrow-follows-bline.sifz‎

Controlling the linear velocity

By default, the arrow travels the whole spline with a constant velocity, independently of the Spline structure.

If you select the Group Layer and look at the Parameters Panel, you'll see that its Origin parameter is converted to "Spline Vertex" type. This is done automatically when "Link to Spline" is executed.

You can disable the "Homogenous" subparameter and then the speed of the arrow will depend on the Spline structure, it will take the same time to move along each segment of the Spline. So if there's a long straight segment then a bendy complex part, the arrow will move much faster along the straight segments (since there will be less vertices in that part). In physics terms, the linear velocity (that is, the speed over the Spline) is not constant.

For illustration of the "Homogenous" effect see this demo.

See also


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