Manipulating Objects and Shaders in the 3D Preview

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Terragen allows you to manipulate objects and many shaders in the 3D Preview. This page describes how to move, rotate and scale objects and shaders interactively. Please note that "object" is used below to refer to any node that can be manipulated in the 3D Preview, whether it's an actual object node or a shader.

Objects which can be manipulated will show, at minimum, a set of crosshairs in the preview. These crosshairs are usually at the object origin, which is the location specified by a position parameter, or similar, in the node. Some objects may show additional information. Many show a bounding box. Other examples are the Simple Shape Shader, which can show the outline of its shape, and the Camera which shows a simple camera body and view frustum.

To manipulate an object you first need to select it. When you move the mouse over a selectable object the crosshairs, as well as the object itself, turn yellow. There are a couple of ways to select objects. You can just click on the crosshairs. If you context click in the preview you can also choose any selectable nodes from the "Select Object or Shader" submenu. This may be helpful if there are a number of nodes close together and you're having difficulty selecting the one you're interested in. Only one object can be selected at a time.

When you select a node the transform panel is shown. The transform panel is a set of four buttons that let you choose a manipulator. This is what they look like:

Wwo transform panel.gif

From left to right the buttons are for translation (moving), rotation, scaling and drop-to-terrain. Not all objects support all the transformations. Transform buttons will be greyed out for unsupported transformations.

The default manipulator for most objects is the translation manipulator. You can change to other manipulators by clicking a transform panel button or using the "T" key to switch between them. The drop-to-terrain button doesn't show a manipulator and is described further below. Manipulators are drawn at the object origin.

The translation manipulator draws the X, Y and Z axes in red, green and blue respectively. Each axis has an arrowhead showing the positive direction. The axes highlight when you mouse over them to show what would be selected if you clicked the mouse there. Click and drag on an axis to move the object only along that axis. For example if you click on the X axis the object will only move along the X axis when you drag. To move the object freely in 3D click on the centre of the crosshairs.

Wwo translate handle.gif
Translation manipulator

The rotation manipulator draws a set of circles which typically correspond to pitch (red circle), heading (green circle) and bank (blue circle). This may be different for some nodes which don't rotate in the same way, but it will be true for most nodes which support rotation in 3D. A solid line is drawn to show the axis of rotation for each circle. A blue dotted line is drawn to show the object's positive X axis, which can help show the object's orientation in space.

To rotate an object mouse over the circle for the rotation. The circle that will be selected when you click will be drawn with a transparent fill. Click and drag with a circular movement around the manipulator to rotate.

Wwo rotate handle.gif
Rotation manipulator

The final manipulator is the scale manipulator. The scale manipulator draws the X, Y and Z axes in red, green and blue respectively, along with a ball on the ends of each axis. To scale an object along a particular axis you click and drag on one of those balls. To scale the object along all axes at once (uniform scaling) you click and drag on the purple ball in the centre.

Wwo scale handle.gif
Scale manipulator

Not all objects allow manipulation along all axes. Manipulators only draw handles for the axes that are allowed. An example of this is the Simple Shape Shader, which only allows rotation around the Y axis. The rotation manipulator for the Simple Shape Shader only draws the Y axis circle.

When you've finished manipulating an object you can deselect it by clicking away from the object axes. Alternatively you can choose "Deselect" from the Edit menu. This is also useful if you're having trouble deselecting without selecting something else in the scene.


You can drop objects to the terrain. This makes an object sit on the terrain surface. This might be useful if you find an object is floating above the terrain.

What actually happens is that TG finds the elevation of the terrain at the object position and then sets the Y coordinate of the object's "origin" (or "anchor") point to that elevation. This has the effect of dropping the object down onto the terrain. But keep in mind that the the "origin" is not always at the base of an object, it may be in the center, or even in some other part of the object depending on how it was created. This means that sometimes dropping to terrain can bury the object in the terrain.

You can drop an object to the terrain using the drop-to-terrain button on the transform panel. You can also use the "D" key. If you want to see where the object would sit on the terrain if it was dropped you can press "shift-D" to toggle the drop point display. This draws a crosshair at the drop position on the terrain. You may also find the drop point display useful when trying to position objects in the air relative to a point on the terrain.

Wwo drop point.jpg
Object showing drop point in orange

Back to Working with Objects

A shader is a program or set of instructions used in 3D computer graphics to determine the final surface properties of an object or image. This can include arbitrarily complex descriptions of light absorption and diffusion, texture mapping, reflection and refraction, shadowing, surface displacement and post-processing effects. In Terragen 2 shaders are used to construct and modify almost every element of a scene.

A parameter is an individual setting in a node parameter view which controls some aspect of the node.

A single object or device in the node network which generates or modifies data and may accept input data or create output data or both, depending on its function. Nodes usually have their own settings which control the data they create or how they modify data passing through them. Nodes are connected together in a network to perform work in a network-based user interface. In Terragen 2 nodes are connected together to describe a scene.

The bounding box is a box which surrounds (or bounds) an object or shader. This box shows the maximum extents of the item inside it. Sometimes abbreviated as "b-box".

Context clicking shows a contextual menu. On Windows this would normally be done with a right click. On OS X this could be a control-click or a right click.