Layers

Maps show drawings, images, surfaces and labels components stacked in layers.

images/line_layers.gif

The "empty space" in drawings and labels components is transparent so objects in lower layers can be seen. Any layer may be made partially transparent so items underneath the "solid" parts of the layer may be seen as well.

Layer Tabs

Maps show layer tabs at the bottom of each map window. The layer tabs are automatically named the same as the drawing or image they contain. The leftmost tab is the top layer. Layer tabs may be used to manipulate the layers in a map:

Layer Tab Controls

Click on a layer tab to make that layer the active layer.
Double click on a layer tab to turn that layer on / off for display.
Click and drag on a layer tab to move that layer to a different position in the layer stack.
Right click on a layer tab to pop open a context menu of things we can do with layers.

The active layer tab is white. Inactive layer tabs will appear in the color defined in our Windows Desktop Display settings for "3D Objects." Only one layer is active at a time. Selection commands and windows clipboard commands operate on the active layer only by default.

The Layers Pane

The Layers pane provides an alternate user interface for working with layers. The layer tabs at the bottom of each map are convenient when a small number of layers is used in a map. When a map has many layers the layer tabs are inconvenient to use because we must spend a lot of time scrolling left and right through the layer tabs to get to any particular tab.

The Layers pane provides a list of all layers in a map. It is normally left open and docked to the left or right side of the main Manifold window in a vertical orientation. It may therefore be used to keep dozens of layer names in view and to rapidly click on any one of them. For intensive image editing work involving many layers it provides faster control over layer characteristics (such as opacity) as well.

Layers Pane Controls

Double-click on a layer to highlight it and to make it the active layer.
Click on a layer and press the Switch to button in the layers pane toolbar to make it the active layer.
Use the checkboxes to turn layers on and off for display.
Right click on a layer for a context menu for that layer.
Each layer may be set to a percent opacity to specify partial layer opacity.
Move layers up and down in the layer stack with the Move Up and Move Down buttons.
The Border and Background may be turned off and on using their checkboxes.

The Border and Background Layers

The layers pane will always show two additional layers: the Border layer and the Background layer. These are system layers and are not real "layers" in that they do not correspond to any drawing or image in the project. Both may be switched ON or OFF via their checkboxes.

The Border layer shows a border about the maximum horizontal and vertical extent of the map. It is a useful way of checking if any objects are in the map but are not in view.

images/sc_layers_dwg_04.gif images/sc_layers_dwg_05.gif

The Background shows what color to put underneath all other layers. By default white, it may be switched off to easily see if any white space in the map is part of the background or not. The background color for all components is set by default in the Tools - Options dialog. Each individual component can have its background color set to some color different than the default by opening the component in a window and choosing View - Properties. Changing the background color can dramatically change the appearance of a map.

The following three illustrations show the effects of changing only the background color from the default white, to black to green.

images/sc_background_color_01.gif

images/sc_background_color_02.gif

images/sc_background_color_03.gif

It is obviously important to consider background color when choosing formatting colors for objects in drawings. Note, for example, how the black color used for a railroad disappears when black is the background color. The map shown above was intended for use with a green background color, and not with white or black background. (The illustrations show a small region in Texas taken from a declassified US Military map provided by NIMA in VMAP Level 2 format.)

Using Layers to Set the Map Projection

When a map is first inserted into a project, if it is created using only one component the projection of that drawing or image will be used for the map. If a map is created using multiple drawings or images at the same time, then a random choice of one of the native projections of one of the constituent components will be used.

At any time we can change the projection used by a map using the Edit - Assign Projection dialog. If we would like the map to use a specific projection that's used by one of the components used as a layer in the map, we can easily specify the projection to be used by right clicking on any layer and choosing the Use Projection choice from the context menu. The map will automatically switch to using the native projection used by that layer.

Layer opacity

Layers may be given an opacity percentage that applies to the entire layer. As opacity ranges from zero percent to one hundred percent the layer will be either completely transparent or totally opaque.

If an image layer contains an RGBa image where individual pixels may have different degrees of transparency, the layer opacity will be evenly combined in a proportional way with all pixels.

Opacity Dialog

An alternative to setting layer opacity via the % edit box in the Layers pane is to use the opacity dialog that pops up from the context menu for map layer tabs. Right click onto a layer tab and choose Opacity to open the dialog:

images/dlg_opacity.gif

The opacity dialog allows interactive setting of opacity by moving a slider bar. Check the Preview box to see the effect in real time. We can also click into the edit box and change the opacity value number.

Context Menu for Map Layer Tabs

Right click on a layer tab to see the context menu for that layer:

Visible	Show or hide this layer.
Add	Add a new blank drawing, image or labels component using the map's projection, or launch the Layers dialog to add components from the project pane. The component will be added as a layer just above the active layer tab.
Cut	Windows clipboard cut operation. Copy objects or pixels to the clipboard and delete them from the drawing.
Copy	Windows clipboard copy operation. Copy objects or pixels from this layer onto the clipboard.
Paste	Paste the contents of the Windows clipboard into this layer replacing any selected items.
Paste Append	Paste the contents of the Windows clipboard into this layer.
Delete from Map	Delete this layer from the map. The component will continue to exist in the project pane and in any other maps in which it participates.
Duplicate	Make a copy of this component in the project pane and insert it in the map.
Open	Open this component in its own window. If it is already open in its own window, activate that window.
Open in New Window	Open this component in its own window. If it is already open in its own window, open it again in yet another window.
Rename	Change the name of this component
Order	Move layer to top, up, down or to bottom of layer stack.
Opacity	Set the opacity of this layer. See the Layer Opacity topic and the note below regarding the Opacity dialog.
Restrictions	Specify if this layer allows clicking, editing or selecting using mouse commands. See the Layers pane topic for more information on layer restrictions.
Center	Center the active layer in the map window.
Zoom	Zoom to fit the active layer in the map window.
Zoom to Selection	Zoom to fit the selection in the active layer in the map window.
Match	Enabled for image or surface layers. Crop / expand / resample / re-project the active layer so that matches the image or surface specified. Often used to prepare an image so that it is the same size and coordinate system as an another for use as a mask or other purposes.
Register	Move and rescale this drawing to specify its geographic location. A manual operation that is rarely used. See the Georegistration topic for easier methods.
Project to Map	Re-project this layer's component to match the projection currently used in the map. This is a permanent alteration in the data.
Transfer Selection	Transfer selections between components.
Use Projection	Apply the native projection of this component as the projection used by the map.
Properties	View the properties dialog for this layer.

Example

Manifold System has such powerful image manipulation capabilities that it may also be used to create complex images by combining multiple images in layers as is done with professional quality graphics image editors such as Adobe PhotoShop.

images/img_splash_small.gif

For example, the marketing promotion "splash" screen used with 5.x and 6.x series Manifold System releases was created using over 40 layers of other images. Alpha pixel transparency and invisible pixels were used throughout the various layers so lower layers could combine to form the image. Looking at seventeen of the various layers we can see how the image was created:

images/img_splash_stack.gif

The bottom three layers were screen shots from a Terrain window using different settings for sky and surfaces. The uppermost of these is the grid.

The next two layers are the floating city and its shadow, which are in separate layers so that the opacity and relative position of the shadow may be easily controlled. See the Gaussian Blur topic for details on creating drop shadows. The next twelve layers consist of text or logotype images together with various drop shadows.

The actual production "map" for the splash screen included over 40 layers. The extra layers contained variations of the logotype, different visual elements such as different sky cloud patterns and other variations. By checking the layers ON and OFF and moving the various layers about it was easy to try out many different variations to end up with exactly the effect desired.

Each image in the layer stack was heavily manipulated using various effects, resized, partially erased or made transparent to "feather" its features visually into features from other layers, and so on. For example, the city originated in a scanned photograph snapped from the bell tower in St. Mark's square in Venice. It was cut out of the photograph and then different parts of the image had hue, contrast and color balance adjusted in different ways. To bring out detail in the trees the green areas were re-built from several layers using different settings for brightness, contrast, saturation, colorization and color balance.

See the Composing Complex Images in Layers topic for an additional example of how to compose complex images using layers in Manifold.