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Hand Drawing

Branches can be drawn by hand using the mouse or a tablet device. After they are drawn they can be manipulated as Bézier splines and even extended by another hand drawing operation. Hand drawn branches can originate from Tree node (the disk on the ground) or any other branch node (hand drawn or not). Procedural generators can be added to hand-drawn generators, allowing you to be specific where you need to be and still get the benefits of procedural geometry to fill in the details.

Note: Hand drawing has changed for SpeedTree 8 to reduce misplaced branches and allow for better draw plane manipulation. The new approach is to place stubs and then extend them as much as you'd like as described below.

How to Hand Draw a Branch

Follow these steps to get started with hand drawing.

  • Make a new scene using the “Blank” tree template.
  • Hold “Space” and click anywhere on the Tree node disk to place a stub. Your scene should look like the following image at this point. Notice the hand drawing indicator on the new generator.

  • Hold “Space” and hover over the stub. A white diamond should appear at the end like this:

  • While holding “Space”, click and drag the diamond to draw the branch. Release the left button to complete the action.

  • Hold “Space” again and click the trunk in several places to create new stubs. Feel free to rotate the camera around the model to get the stubs where you want them. The stubs will start where you click and point toward the camera. Notice that a new generator is made to house these stubs, again with the hand drawing icon.

  • As before, Hold “Space” and hover over any stub or hand-drawn branch to reveal the white diamond. Click and drag each diamond while holding space to draw the branches.

  • Finally, right-click the Branches generator and select “Add geometry to selected→Bifurcating branches” to add some procedural geometry to the model.

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Continue by adding more stubs to the ground or any branches (hand drawn or procedural). You can draw part of the stub, rotate the camera, and continue drawing it to change the direction of the branch.

Editing the Spine of an Existing Hand Drawn Branch

Switch to node editing mode and select the hand-drawn branch. You should see a series of control points for the spine as pictured below.

Click and drag any of the control points to move them. Alternatively, you can select a control point and use the standard gizmo to move them. Control points have a number of options to aid in spine editing:

Style Choose from “Linear,” “Smooth,” and “Corner” to control the nature of the spine through the point.
Select Use these options to modify which control points are selected. Using “Select:To End” and then using the Rotate gizmo is a good way to quickly rotate the spine.
Add Control Point Use these options to add a new point before or after the selected point.

It is also possible to change how many control points are on the branch all at once. On every hand-drawn generator, a “Hand Drawn” property group exists with two sets of identical functions; Curve fit and Control point style. The options in the “New” group affect only nodes that are created after changing these values. The options in the “Resample” group affect all existing nodes in the generator. Use the options in the “Resample” group if the density of control points is either too high or too low.

Note: The “Resample” group exists as node properties as well. Entering node selection mode will allow you to resample a single hand drawn spline without resampling the entire generator.

Curve Fit

“Curve fit” is a scalar for the number of control points used to create the spline. A value of 1 results in an accurate spline that may have many control points based on the speed of drawing and other factors. Values less than 0.5 become inaccurate but have control points that are easier to work with (since each branch is composed of only a few control points). If using a low curve fit value, set the control point style to “Corner” to ensure the best accuracy with only a few points. You can always resample or add more control points later if necessary.

Control Point Style

Controls points are generated in either a corner, linear, or smooth style. Both linear and smooth control points have linear handles (each handle points 180° away from its counterpart), but smooth control points have the extra limitation that they must be of the same length. Smooth is best suited for flowing branches without sharp jinks, since jinks are hard to reproduce with equidistant, linear points.

Converting Procedural Branches to Hand Drawing

It is possible to convert procedural branches to hand-drawn branches (but not the other way around). The entire generator will be converted so be careful. Converting 100,000 twigs on a VFX model to hand-drawn branches would likely be prohibitively slow to compute.

Use either the “Convert to Hand Drawn” button on the generator or the “Hand Drawing→Convert to hand-drawn” option in the Generation Editor menu to make the conversion.

Working With Hand Drawn Generators in the Generation Editor

Complex hand-drawn models may require extensive work in the Generation Editor to ensure that branches are drawn into the correct generator. Please use the following guidelines to predict and control the hand drawing workflow.

New Branches

New branches are placed according to the following guidelines:

1. If no hand-drawn generator is present in the target branch level, a new hand-drawn generator is created. The template used for new hand-drawn generators is located in the “Templates/Hand Drawn” sub-folder of the SpeedTree Modeler install directory. A separate template is used for trunks (branches drawn from the tree radius).

2. If a hand-drawn generator is present, new hand-drawn branches will be put into that generator.

3. If more than one hand drawn generator is linked from the parent node, one of the hand-drawn generators must be designated as the “hand drawn target” in order to receive new branches (see this section below for more).

Like all other generators, hand-drawn generators can be saved off and loaded as template (STT) files. When a hand-drawn template is loaded in the Generation Editor, it is signified by a “drawing hand” icon overlay in the bottom right-hand corner of the generator icon.

Note: Hand drawn templates can be used effectively by linking an entire tree together (i.e. a trunk, level 1, and level 2 branches) made completely of hand drawn templates before drawing a single branch.

Paste Into

“Paste into,” accessed via the right-click menu of a selected icon in the Generation Editor, will paste a copied generator's contents into another generator – even after nodes have been drawn. It will paste all of the properties except for the generation components. This is useful for quickly replacing the settings in a hand-drawn generator after branches have already been drawn. It is also great to use when there are node edits on child branches that you don't want to unlink and lose.

Copying and Pasting Hand Drawn Generators

Hand drawn generators can be copied and pasted the same as any other generator. A pasted copy of a hand-drawn generator will contain no branches until you draw them.

Resetting a Hand Drawn Generator

Using “Clear node edits” in the Generation Editor menu or unlinking/relinking the generator will reset its contents. After either of these operations, there will be no hand drawn branches in the generator until you place new stubs.

Hand Drawn Targets

The first hand-drawn generator created in a branch level is automatically the designated “target”. The target is indicated with a checkmark ('√') next to the hand-drawn icon overlay. However, the target can be manually turned off via the “Hand Drawing→Draw into selected” option in the Generation Editor right-click menu. Once the target has been disabled for a branch level, a new hand-drawn generator will be created the next time new branches are drawn on that level. The target can also be moved between existing hand drawn generators, but only a single target is allowed per shared parent at any given time.

Locking Hand Drawn Sources

Occasionally you may want to “lock” a generator so that hand drawn branches cannot be generated as children. This may be true with a complex tree where it is difficult to tell which generator a particular branch belongs to. By locking a generator (“Hand drawing→Toggle lock on selected” in the Generation Editor right-click menu), hand drawing new children will be prohibited off of it.

Best Practices

The following list outlines a few things to keep in mind when hand drawing branches.

  • The “Spine:Noise:Late” noise works on hand drawn branches. Use this to your advantage! Keep your branch drawing smooth and simple and use noise to rough them up. It's a good idea to use the “Round” preset on the noise profile so that the beginning and end of the branch are right where you put them.
  • All of the skinning properties still work procedurally. Radius, displacement, welding, etc. are all manipulated in the same manner as regular branches.
  • Forces work…if you allow them! They will, however, pull the branch off of the drawn spline.
  • You can move the start position and angle using the Art Director gizmo handles. You can also manipulate the properties directly.
  • Hand drawn branches work in the subdivision surface system.