Créer des formes

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Revision as of 19:36, 25 September 2011 by Marceld (Talk | contribs) (L'outil BLine)

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Les primitives de base telles les cercles ou les rectangles sont toutes merveilleuses, mais plutôt rigides géométriquement parlant. Pourquoi pas créer des formes plus élaborées ? Pour ce faire on utilise l'outil BLine.

L'outil BLine

Dans Synfig l'élément de description des formes est appelé BLine. C'est grossièrement analogue à ce que d'autres programmes intitulent "chemin" sauf qu'il s'agisse exclusivement de Spline hermites.

Reset Colors button in the Toolbox
Avant de commencer avec le tutoriel de BLine ajoutons quelques élements complémentaires sur la façon de fonctionner de Synfig. Quand vous cliquerez sur l'outil Bline (BLine Tool/fr), vous vous apercevrez que les sommets de l'objet en cours de sélection (si il en existe un) vont disparaître, mais que le calque correspondant restera sélectionné dans le Panneau des Calques (Panneau Calques). C'est normal. Quoique vous fabriquiez avec l'outil BLine sera inséré au-dessus du calque en cours de sélection. Gardez en mémoire que si vous voulez insérer une forme quelque part, vous devrez sélectionner exactement où vous voulez l'insérer avant d'activer l'outils BLine — changer de sélection après-coup vous renverra automatiquement dans l'outil de transformations ( Transform Tool).

Now, go ahead and click on the "Reset Colors" button in the lower left corner of the FG/BG color widget in the toolbox. This will reset us back to the default black and white. Also, set the default line width to something nice and thick — 10pt should do the trick.

After you switched to BLine tool, take a look at the Tool Options Panel. Make sure that only "Create Region BLine", "Create Outline BLine" and "Link Origins" are checked.

Clicking with your mouse in the canvas will place vertices. While you are placing a vertex, you can drag out its tangent by dragging the mouse. Do this over and over, and you construct a BLine.

Keep in mind, however, that during this construction, there is nothing stopping you from just moving it if you don't like where you placed a vertex or a tangent. Honest! If you want to remove a vertex, right click on it and select "Delete Vertex". Want to split the tangents? Right click on the tangent and hit "Split Tangents". Want to loop the BLine? Right click on the first vertex and select "Loop BLine".


When you are finished placing vertices, you must exit construction mode in order to actually create the BLine layer(s); there are 2 ways to do this:

  1. Switch to another tool.
  2. Press the "Create" button at the bottom of the Tool Options Panel (it's the icon that looks like a gear).

For now, just go ahead and switch to the Transform Tool, because we are done with the BLine Tool.


Editing BLines

Ok, we now have a nice pretty white region with a thick black outline. Since we checked "Create Region BLine" and "Create Outline BLine" in previous steps, you'll notice that there are two layers that we have created — the Outline and the Region in the Layers Panel. Despite the fact that they are two separate layers, their vertices parameter has already been linked — so you can select either one and move its ducks around and the other one will also change.

If you want to manipulate the vertices after you have created the layers, it is very easy to do so. Just click on one of the layers and have at it. If you want to remove a vertex, right click on it and hit "Remove Item (smart)". Want to insert a point somewhere? Right click on the segment where you want to insert something and hit "Insert item (smart)".


The only major difference between this normal editing mode and the construction mode is in how you split the tangents — in construction mode you right click on the tangent itself. In normal duck editing mode, you must right click on the vertex to which the tangents are attached. This could be considered a usability bug, and it will be resolved at some point.
note end

This may appear to be leading to a mess of layers. And yes, if you aren't using the software properly, that is exactly what you will get. But there is a way to make this more sane. As mentioned in the previous tutorial, you can encapsulate layers into hierarchy.

One quick thing to mention before I finish up. You can change the width of an outline at each vertex. You do this by selecting the outline layer (NOTE: you must select the Outline Layer, the Region Layer has no width data) and tweaking with the width ducks. By default, these are masked. To show them, press Alt5 or click "Toggle width ducks" button at the top of the canvas window (the fifth one from the left). Repeat to hide them again. You can also see other things to mask via the Menu chevron du Caneva: "View → Show/Hide Ducks".

Using tablet to draw shapes

If you have a graphic tablet you can use Draw Tool to create BLines.

Synfig Studio supports pressure sensitivity, but you need to configure it first. Go to "File → Input Devices..." from toolbox menu. In the Input dialog find your tablet's stylus device and set its mode to "Screen". Click "Save" and then "Close".

Now grab your stylus, create a new file and click on the Draw Tool button in the toolbox. Set the default line width value to be big enough — say, 15pt — otherwise you will not notice any pressure sensitivity effect. Choose brown as the default fill color.


Steps above should be done with the stylus of your tablet, not the mouse. Synfig Studio remembers settings for each input device independently. That's why if you set those options with your mouse device they will not have any effect when you switch to stylus.
note end

In the Tool Options Panel, make sure that you have the same options as shown on the screenshot below.


Now let's draw some thing like a curvy mountain background. Start drawing a line from the left border to the middle of the canvas. Try to vary your stylus pressure while you are drawing. Stop near the center of the canvas. This is your first line. Notice the new outline layer created in the Layers Panel.


Point your stylus at the last duck of your new BLine and continue drawing to the right border of the canvas. When you finish, look at the Layers Panel again. There's still only one outline layer. Synfig Studio is smart enough to figure out that you don't need a new outline layer and properly extends the last one. You can extend the BLine from both ends, but if you start drawing from any other place of the canvas a new outline layer will be created. Though your first line will remain selected and nothing stops you from extending it later.

Back to our artwork. In the Tool Panel hit the button with the bucket icon to fill the outline we just created. A region layer will appear at the top of the layer we are working with. Select the outline layer and press the "Raise Layer" button in the layers panel to put the outline layer on top of the region.


Extend a line from both sides down to the corners of the canvas to make the fill appear at the bottom. Great.


Go ahead and add a few more lines on top of the filled area to give it a mountain-like look. If brown ducks are in your way, you can hide them by clicking the "Toggle vertex ducks" button at the top of the canvas window (the second one from the left).



Don't use Alt2 shortcut to turn off visibility of vertex ducks while you using Draw Tool. There's a bug that will cause Synfig Studio to hang.
note end
Development Notes:

This bug is fixed in the upcoming release (0.63.00).

Draw tool is great for drawing complex shapes, but you end up with a bunch of ducks, which are hard to manipulate with the Transform Tool in the way we described above. There are two solutions here.

First, you can increase the "Smooth" value in the Tool Options Dialog while using Draw Tool. That will reduce the count of vertices produced at drawing time, but will make your shape less detailed.

Second, you can use Smooth Move Tool to deform an existing shape. Go for it and click the Smooth Move Tool button in the toolbox. The trick about this tool is that it affects selected ducks only. Press and hold your left mouse button in an empty place of the canvas. Drag to create a selection box. Release the mouse button when you are done. Or just hit CtrlA to select all ducks. Now you can deform the selected segments of BLines. You can change the size of the influence area by tweaking "Radius" in the Tool Options Panel.

What about outline width? There is a Width Tool for that purpose. It is designed for increasing or decreasing the width of a line much like you would with a pencil on paper. Click the Width Tool button in the toolbox, move your stylus over the line you want to change, press and move the cursor back and forth along the line, like you are scratching something. The width of the outline will be increased at the places where you moved the cursor. If you want to decrease the width, just hold "Ctrl" while scratching. Easy!

If you don't want Width Ducks to be displayed, during usage of the Width Tool, just turn them off by pressing the "Toggle width ducks" button at the top of the canvas window.


Don't use Alt5 shortcut to turn off visibility of width ducks while you using Width Tool. There's a bug that will cause Synfig Studio to hang.
note end
Development Notes:

This bug is fixed in the upcoming release (0.63.00).

Other ways to create BLines

Is that all? Not yet. You can use Circle, Rectangle, Star and Polygon tools to create BLines too. Just check the "Create Outline BLine" and "Create Region BLine" options in the Tool Options Panel when using those tools.

Creating geometric primitive as BLine gives you a better control over it's shape and look. For example, if you want a deformed star, then you can use the Star Tool to create it as outline and region BLines and then use the Transform Tool to deform it.

Now you are ready for the last tutorial in this section. Hang on!

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