# Difference between revisions of "Convert"

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Right-clicking on a value in the Parameters dialog brings up a context menu which has a sub-menu called "Convert". The "Convert" menu allows you to specify that the parameter should be controlled automatically in various ways. Depending on the type of the parameter the Convert menu will contain different options.

To convert the value back to its original type, select "Disconnect" from its context menu.

## Convert Types

Converting a parameter to "Add" adds three sub-parameters, the first two of which are the same type as the parameter itself:

• <param> "LHS"
• <param> "RHS"
• real "Scalar"

The "Add" conversion can be used with parameters of type angle, color, integer, real, time, and vector.

The resulting value is:

```  (LHS + RHS) * Scalar
```

### aTan2

Converting an angle-valued parameter to "aTan2" adds two sub-parameters:

• real "X"
• real "Y".

The resulting value is:

```  atan2(y,x)
```

ie. atan(y/x) but without an error when x is 0. The value is the angle between the x axis and the vector (x,y).

### BLine

Converting a list parameter to "BLine" doesn't seem to change anything. Perhaps that's the default type for lists of vertices, such as are found in outlines and regions?

### BLine Tangent

Converting a angle or vector parameter to "BLine Tangent" adds three sub-parameters:

• bline "BLine"
• bool "Loop"
• real "Amount"

Amount is a number between 0 and 1, defining the distance along the given bline. The resulting value for the whole parameter is the tangent to the bline, at the given point along the bline, either as an angle or as a vector, depending which type was converted.

This tutorial gives an example of the use of this convert type.

### BLine Vertex

Converting a vector parameter to "BLine Vertex" adds three sub-parameters:

• bline "BLine"
• bool "Loop"
• real "Amount"

Amount is a number between 0 and 1, defining the distance along the given bline. The resulting value for the whole parameter is a vector giving the position of the given point along the bline.

This tutorial gives an example of the use of this convert type.

### Composite

Converting a blinepoint parameter to "Composite" adds six sub-parameters:

• vector "Vertex"
• real "Width"
• real "Origin"
• bool "Split Tangents"
• vector "Tangent 1"
• vector "Tangent 2"

Converting a color parameter to "Composite" adds four real-valued sub-parameters:

• real "Red"
• real "Green"
• real "Blue"
• real "Alpha"

Converting a segment parameter to "Composite" adds four vertex sub-parameters:

• vertex "Vertex 1"
• vertex "Tangent 1"
• vertex "Vertex 2"
• vertex "Tangent 2"

Converting a vector parameter to "Composite" adds two real-valued sub-parameters:

• real "X-Axis"
• real "Y-Axis"

The resulting value is a blinepoint, color, segment, or vector made by combining the component parts.

### Cos

Converting a real-valued parameter to "Cos" adds two sub-parameters:

• angle "Angle"
• real "Amplitude".

The resulting value is:

```  Amplitude * cos(Angle)
```

### Dynamic List

Converting a list parameter to "Dynamic List" seems to replace each of the "Vertex NNN" sub-parameters with "Item NNN" parameters which can't be expanded, but can be exported.

### Exponent

Converting a real parameter to "Exponent" adds two sub-parameters:

• real "Exponent"
• real "Scale"

The resulting value is the result raising the mathematical constant 'e' to the power of Exponent, and scaling the result by Scale. That is, it returns:

``` Scale * e^Exponent
```

This is useful for tracking layers which have been zoomed, since the Zoom layer scales by e^(zoom factor).

See this video for an example of the use of this convert type.

• real "Offset"

The resulting value is a gradient based on the "Gradient" parameter, but shifted left (for negative values) or right, according to the value of the "Offset" parameter. An offset of 1.0 will shift the gradient by its entire visible width. Values shifted off the left or right edge aren't lost - they aren't visible in the gradient as it's displayed in the parameters dialog, but they will still be used when rendering (depending on parameters such as 'Loop' and 'Zigzag', which can cause gradients to be looped between their their left and right edges, rather than using the non-displayed parts).

### Linear

Converting an angle parameter to be 'Linear' adds two angle sub-parameters:

• angle "Rate"
• angle "Offset"

Converting a color parameter to be 'Linear' adds two angle sub-parameters (since svn r617):

• color "Rate"
• color "Offset"

Converting an integer parameter to be 'Linear' adds two angle sub-parameters (since svn r617):

• integer "Rate"
• integer "Offset"

Converting a real parameter to be 'Linear' adds two real-valued sub-parameters:

• real "Rate"
• real "Offset"

Converting a time parameter to be 'Linear' adds two time sub-parameters:

• time "Rate"
• time "Offset"

Converting a vector parameter to be 'Linear' adds two vector sub-parameters:

• vector "Slope"
• vector "Offset"

The parameter's value will change linearly over time, starting with the value specified by "Offset" at time zero, and increasing by the value specified by "Rate" (or "Slope", in the case of vector parameters) every second.

The resulting value for vector parameters is:

```  Offset + Slope*time
```

and for the other 5 types of parameter it is:

```  Offset + Rate*time
```

• real "Luma"
• real "Saturation"
• angle "Hue"
• real "Alpha"

• angle "Theta"

For color parameters, the resulting value is the color with the given lima, saturation, hue, and alpha amounts.

For vector parameters, the resulting value is the point reached by traveling a distance "Radius" from the origin, in the distance given by the angle "Theta".

### Random

(currently only in subversion)

Converting a parameter to "Random" adds five sub-parameters, the first of which is the same type as the converted parameter:

• integer "Seed"
• real "Animation Speed"
• integer "Interpolation"

"Random" can be used on angles, colors, integers, reals, times, and vectors.

It is used to cause a parameter's value to vary randomly over time, around a central value:

• "Link" provides the central value.
• "Radius" defines the maximum random difference.
• "Seed" seeds the random number generator
• "Animation Speed" defines how often a new random value is chosen (in choices per second)
• "Interpolation" determines how the value is interpolated from one random choice to the next. Possible values are:
• 0 - no interpolation; the value jumps from one value to the next
• 1 - linear interpolation
• 2 - cosine
• 3 - spline
• 4 - cubic (the default); uses Catmull-Rom spline interpolation

The "Interpolation" sub-parameter should really be a drop-down menu, rather than an integer field, but that isn't yet implemented.

### Range

Converting a parameter to "Range" adds three sub-parameters, all the same type as the parameter itself:

• <param> "Min"
• <param> "Max"

"Range" can be used on angles, integers, reals, and times.

It is used to limit the value of the linked parameter to be between Min and Max.

The resulting value is:

```  Min (if Link < Min)
```

### Reference

Converting a parameter to "Reference" adds a single sub-parameter called "Link". The "Link" parameter is the same type as the parameter being converted.

It doesn't seem to do anything at all, other than adding an extra parameter. Whatever value is put into "Link" becomes the value of the parameter being converted.

The only use for this conversion type I can think of is the following:

• you know that point A should follow point B, so you export point B and connect point A to it
• you're not yet sure exactly how point B should move, so you experiment with different conversion types for point B
• changing the conversion type for point B breaks the connection you made in the first step
• converting point B to be a reference, and then experimenting with different conversions in its "Link" parameter allows point A to connect to point B and for the connection to remain in place while you experiment in the "Link" parameter

The resulting value is:

```  Link
```

• integer "Count"
• real "Width"
• bool "Specify Start"
• bool "Specify End"
• color "Start Color"
• color "End Color"

The resulting value is a gradient containing "Count" equally spaced, equally wide copies of gradient "Gradient". Each copy has "Gradient" going forwards and then backwards. "Width" specifies relative width of the forward copy, with a width of 0 or less meaning only the backward copy is used, and a width of 1 or more meaning only the forward copy is used. A value of 0.5 will result in the forward and reverse copies of "Gradient" being the same width.

If "Specify Start" is checked then "Start Color" will be inserted at the beginning of the new gradient, otherwise the beginning of "Gradient" will be used as the beginning of the new gradient.

If "Specify End" is checked then "End Color" will be appended to the end of the new gradient, otherwise the end of "Gradient" will be used as the end of the new gradient.

Here's an example of a repeated gradient - the radiating green/yellow lines are a repeated gradient, applied to a perpendicular curve gradient. This gradient was repeated with a width of 0.5, meaning it is used backwards and forwards the same amount:

and here's the resulting image, along with the .sif file:

### Scale

Converting a parameter to "Scale" adds two sub-parameters: one called "Link", of the same type as the parameter itself, and a real-valued parameter called "Scalar".

• real "Scalar"

"Scale" can be used on angles, colors, integers, reals, times, and vectors.

The resulting value is:

```  Link * Scalar
```

### Segment Tangent

Converting a vector parameter to "Segment Tangent" adds two sub-parameters:

• segment "Segment"
• real "Amount"

Amount is a number between 0 and 1, defining the distance along the given segment. The resulting value for the whole parameter is the tangent to the segment, at the given point along the segment.

### Segment Vertex

Converting a vector parameter to "Segment Vertex" adds two sub-parameters:

• segment "Segment"
• real "Amount"

Amount is a number between 0 and 1, defining the distance along the given segment. The resulting value is the vertex at the given point along the segment.

### Sine

Converting a real-valued parameter to "Sine" adds two sub-parameters:

• angle "Angle"
• real "Amplitude".

The resulting value is:

```  Amplitude * sin(Angle)
```

### Stripes

• color "Color 1"
• color "Color 2"
• integer "Stripe Count"
• real "Width"

The resulting value is a gradient containing "Stripe Count" equally spaced, equally wide stripes of color "Color 2" with a background of "Color 1". "Width" specifies the width of the stripes, with a width of 0 or less meaning they are invisible, and a width of 1 or more meaning the whole gradient is of "Color 2".

### Subtract

Converting a parameter to "Subtract" adds three sub-parameters, the first two of which are the same type as the parameter itself:

• <param> "LHS"
• <param> "RHS"
• real "Scalar"

The "Subtract" conversion can be used with parameters of type angle, color, integer, real, time, and vector.

The resulting value is:

```  (LHS - RHS) * Scalar
```

### Switch

Converting a parameter to "Switch" adds three sub-parameters:

• bool "Switch"

"Link Off" and "Link On" are the same type as the parameter being converted.

The resulting value is the value of "Link Off" when "Switch" is off, and "Link On" when "Switch" is on.

This conversion can be used on all value types.

### Timed Swap

This convert type was disabled in Synfig 0.61.06 and earlier because it didn't work.

Converting a parameter to "Timed Swap" adds four sub-parameters:

• <param> "Before"
• <param> "After"
• time "Swap Time"
• time "Swap Duration"

"Before" and "After" are the same type as the parameter being converted.

This conversion type linearly switches from "Before" to "After", taking "Swap Duration" seconds to do so, and completing the swap at "Swap Time".

Note that this doesn't give us anything that we can't achieve using the "Linear" conversion type and a few waypoints, except that it works on more types than the somewhat restricted "Linear" conversion. The "Linear" conversion could be extended to work on the missing types.

"Timed Swap" can be used on angles, colors, integers, reals, times, and vectors.

The resulting value is:

```  if time > "Swap Time" then "After"
else if time < ("Swap Time" - "Swap Duration") then "Before"
else interpolate between "Before" and "After"
```

### Two-Tone

• color "Color1"
• color "Color2"

The resulting gradient has two CPoints, one at each end, starting with "Color1" and ending with "Color2".

These color parameters can be animated, giving us the ability to have the gradient change color over time. This can be used as a workaround for this bug.

## Which Value Types can use which Convert Types?

There are 13 different types of value in Synfig. Each of these types has a different set of convert types available to it, as follows:

### Vector

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