View source for The 3D Preview

== About the 3D Preview == 

The 3D preview shows a preview of your current scene. It provides a simplified yet accurate view that renders quickly. The preview will update with every change you make to the settings of your scene, including any node settings. 

[[File:FirstScene_-_3D_preview_pane.png|border|900px|The 3D preview]]
<br><br>

== Navigating in the 3D Preview ==
 
The 3D preview defaults to the perspective of the current render camera. You can freely change the camera perspective using either mouse and keyboard commands or the navigation tool.

=== Navigating with Mouse and Keyboard Commands ==

The controls for navigating with the mouse and keyboard are as follows:

* '''Alt+Left Click:''' Hold down these buttons and drag the mouse to rotate the camera. Drag down to rotate the camera up, drag up to rotate the camera down, drag right to rotate the camera right, and drag left to rotate the camera left.



The elements displayed in the 3D preview depend on the layout you're in. For example, in the Terrain layout, shaders, atmosphere, and lighting are disabled. This speeds up the preview and gives you a clear view of your landscape. You can control which elements are shown at any time with the 3 middle buttons on the top toolbar signified by a green sphere, a cloud shape, and a sun icon, which enable and disable Shaders, 
Atmosphere, and Lighting respectively. When enabled, these buttons will appear depressed and shaded.
 
To the left on the top toolbar are the 'Pause' and 'Reset' buttons. Since the '3D Preview' is constantly updating to show you the results of every change, it is always taking CPU resources. If you have a lot of changes in mind and want to wait until you are finished with them, you may wish to pause the preview rendering until you are finished. 'Pause' can also be useful when using the Painted shader and painting in the preview window. The 'Reset' button simply resets the preview and begins rendering from scratch, which can be useful if you want to immediately trigger a refresh of the preview for any reason.
On the far right of this toolbar are the 'Painted Shader' and 'Measurement Tool' buttons, signified by a paintbrush and ruler, respectively. We'll cover the 'Measurement Tool' first, because it is simpler. Clicking the 'Measurement Tool' button will enable a measurement system that allows you to measure the distance between two points in the '3D Preview' simply by clicking. When enabled, a measurement window will pop up with a display of the distance between the currently selected points, as well as some additional controls. Simply click in the preview to define the first point of your measurement, then move to your destination point and click again. You will see a yellow line extend between the two points and distance will be displayed in the 'Measure' window. You can also restrict the measurement axis to x, y, or z, as well as clear the current measurement points (note that you may need to reset the preview window to remove the display of the current measurement). During measurement you can use the normal camera navigation controls, so if you have switched into measurement mode and wish to measure something outside of the current view, you can still move your camera to accommodate that. To exit measurement mode, either close the pop-up 'Measure' window, or click the 'Measurement Tool' button again.
 
The Measurement Tool in use
The 'Painted Shader' tool and the associated Painted shader node are one of the most powerful systems in TG2. The Painted shader allows you to control virtually any aspect of your scene simply by painting in the preview window. You can create terrain shapes, control texture distribution, even create customized cloud shapes. The painting system relies on two elements – the Painted shader and paint strokes created in the preview window with the use of the 'Painted Shader' painting tool.
Pressing the 'Painted Shader' button brings up a menu of options. In its non-active state, the only option is 'Start painting shader', which has a sub-menu allowing you to either select an existing Painted shader to paint into, or create a new one and begin painting. Your existing Painted shaders will be listed at the top of this menu, above the 'Create and paint new shader' option. To begin a painting session simply select either an existing Painted shader, or create a new one with the menu option.
Once in a painting session the 'Painted Shader' button displays different options. You can switch between 'Paint mode' and 'Erase mode', where paint mode applies the current brush settings (specified in the Painted shader itself), and erase mode uses the same brush settings, but applies an inverse effect to your paint strokes, removing existing painted areas where you apply the erase effect. You can also use the 'Stop painting shader' button to stop your painting session.
After paint mode is enabled, the settings window for the selected Painted shader will be opened, allowing you to adjust settings like 'Brush size', 'Brush falloff', 'Flow', and 'Colour'. Please refer to the Node Reference for complete information on all Painted shader settings. In the '3D Preview' a yellow dashed circle is displayed denoting the maximum area of your paint brush. The actual size of the painted stroke will be affected by the 'Falloff' setting in the Painted shader. As you move the cursor around the preview window you will also see terrain polygons highlighting under the cursor position. This denotes the rough center of the painted shader, and thus the center of the area at which the stroke would begin. To start painting, click the Left Mouse Button and drag. You can make as many strokes as you want, however note that 'Undo' does not undo specific strokes. Rather it will simply revert the scene to a state prior to beginning your 'Painted Shader' session. You can use the 'Eraser mode' to remove strokes created in error. More on use of the Painted shader is covered in the Node Reference and Shaders In-depth section later in this guide.
Finally, to the right of the 'Painted Shader' and “Measurement Tool' buttons is a display of the current update status of the '3D Preview'. Since the preview is rendered progressively, it is helpful to know what detail level the preview is currently displaying. The detail level will be displayed numerically, beginnign with 'Rendering... detail 5', then doubling to 10, 20, 40, and finally 80. To save time and CPU resources, the preview has a set limit on the maximum detail, so once 80 is completed it will stop updating until another change is made. When rendering has completed, the update status will show 'Finished rendering'.
A helpful technique when using the 'Painted Shader' tool is to allow the preview to fully compute to maximum detail, then press the 'Pause' button and begin painting. This allows for maximum detail in viewing your painted strokes, and also prevents the preview from updating while you're painting which can make painting consistent strokes more difficult.
Below the top toolbar in the upper-left is a mini-compass which shows both your current camera orientation (the top of the compass icon) and the position of any lights in the scene (represented by small yellow circles). Below that is a button to access the exposure slider, which allows you to adjust the exposure value of the current camera. In the upper-right is a button which accesses a navigation panel. Finally, at the bottom is a toolbar which contains the camera selection button and other controls, as well as a display of numerical coordinate data about the scene.
The '3D Preview' is the primary way you will move the camera(s) in your Terragen 2 scenes. You can easily move the current view with the appropriate hotkeys, or use the navigation panel in the upperright. Refer to the 'Help Menu' under 'Mouse and Key Settings' for a list of hotkeys for your platform. With the Windows defaults, most movement actions are accomplished by holding down Alt, then clicking and dragging with one of the mouse buttons in the 3D view. Alt+Left mouse button controls Rotation ("Orbit"), the Middle mouse button controls Forward and Backward motion (like Zooming), and the Right button moves you Up and Down and Side-to-side (a bit like “panning” or "translation"). You can also move forward and backward with finer control by using the mouse wheel.
In the upper-right of the '3D Preview' is a small circle with 4 arrows at the sides. When clicked, this pops open the 'Navigation Panel', a set of visual navigation controls which allow you to manipulate your camera's view with more precision, control, and options. Mouse over each control for a tooltip that will tell you how it affects the camera's position (note: you may need to turn on 'Show Special Tooltips' in the 'General' section of the 'Preferences', accessed from the 'Edit menu'). You can also refer to the User Interface Reference for complete details on the 'Navigation Panel'. You can open the 'Navigation Panel' in a separate floating window with the 'Navigation Window' option on the 'View' menu.
It is important to be aware that changing the current view with either of these methods will not change the current camera position and orientation, as defined in the current Camera node in your scene. Instead it affects the 'Perspective view', one of a set of standard cameras provided by the '3D Preview' which are not linked to any camera node. These views are 'Perspective view', 'Top view', 'Bottom view', 'Front view', 'Back view', 'Left view' and 'Right view'. You can access each of these views by clicking the 'Select Camera' button second from the right on the toolbar at the bottom of the '3D Preview'. Clicking this button will open a list of available views, including 'Current render camera'.
In order to set the render camera view to that which you have specified in the '3D Preview', you must use the 'Copy to current camera' button at the far left of the bottom toolbar in the '3D Preview'. This button will highlight whenever changes are made to the current view which are not reflected in the current camera. Pressing this button will sync the perspective camera with the current render camera. If you do not copy your current view to the render camera before you begin a render, your render will use the existing camera position and may not match your preview perspective.
At the bottom of the preview window is a set of 4 numbers labeled “x,” “y,” “z,” and “slope.” These will only appear when your mouse is positioned over the preview window. The x, y, and z figures indicate the current position of the scene element (usually the terrain) under the mouse cursor in the preview. Coordinates are measured in metric units, usually meters (‘m’) or kilometres (‘km’) and are relative to the coordinate origin. Slope indicates the slope of the terrain in that area and it is measured in degrees. Move the mouse around in the 3D preview and you will see the values update. These numbers can be extremely helpful in placing objects or fine-tuning surface mapping. The slope readout can be particularly useful in determining surface placement and distribution. In addition, you can easily copy these values into relevant settings in a particular node by right-clicking in the preview and selecting to copy the desired data (altitude, coordinates, or slope angle), then using the 'Paste button' next to an appropriate setting in a node. You can open this coordinate display in a separate floating window with the '3D Preview Location' option on the 'View' menu.
In addition to the 'Copy to current render camera' and 'Select Camera' buttons, the bottom toolbar includes several other useful functions. Next to 'Select Camera' is the 'Reset Camera' button, which provides several options for resetting the view shown by the '3D Preview'. You can 'Reset to current render camera', 'Centre on focus point' (the focus point is set with the next button on the toolbar), 'Centre on object or shader', or 'Centre on origin' (the coordinate origin: 0,0).  Remember that, like any change in the view shown in the preview window, you must press 'Copy to current render camera' to save your view in the current camera in order to use it in rendering.
Next is the 'Look at point' button, which specifies the preview's “look at point,” a point in the scene toward which the camera will be oriented. Click the button then point and click on any part of the scene. You will see the polygon under your cursor highlight in yellow to indicate which polygon will be selected as the “look at point.” When you click, your camera will re-orient toward the selected point. This point is maintained throughout a session and you can use the command on the 'Reset Camera' button menu to recall your view to this point at any time.
The last two buttons on the 'Bottom Toolbar' are both related to the camera “orbit” mode. The first allows you to select the “orbit point” in much the same way as the “look at point” function described above. The orbit point defines the point which the camera will reference when orbiting. The next and final button simply activates “Free Orbit Mode,” which allows the camera to roll freely during orbit movements, rather than being fixed to the original roll orientation. This is particularly useful when navigating with the camera at points far from the coordinate origin, for example on the other side of a planet, where the original roll value will not be parallel to the planet's surface.
For further information on all functions and settings for the '3D Preview' please see the User Interface Reference.