8. Viewing a Show as a Path

The time chart shows each axis on its own against time. On a machine whose axes work together, such as an X-Y gantry or a pan/tilt head, the more useful picture is often the axes drawn against each other: the path the machine follows. The path view draws two or three axes this way, with time marked along the path.

The path view only shows your show. Nothing about how takes are recorded, saved or sent to the motors changes. The motors start together, and each follows its own smooth curve through its take, so the path view pairs those curves moment by moment: what you see is the path the motors run. If one axis's take is shorter than the others, that axis holds its last position for the rest of the show.

Choosing a layout

The layout bar above the chart area, on the Shows and Test tabs, sets what the chart area holds. Choose one under Layout:

In Side by side and Stacked, drag the splitter between the panes to change their sizes, and click the arrows beside the layout buttons (Swap the panes) to change their places. Swap is unavailable in Time and Path. Side by side and Stacked each keep their own split. The layout, Swap and both splits are remembered between runs on this PC; they aren't saved in the project.

While the point editor is open, Path shows as Side by side, because editing needs the time chart (see chapter 11).

Axis groups

An axis group says which axes to draw: an X axis, a Y axis and, for a 3-D path, a Z axis. A project can have several groups, for example one for an X-Y table and one for a pan/tilt head. The list in the layout bar's Axis group section picks the one drawn. The layout bar's path sections (Axis group, Colour by and 3-D view) are there only while the path view is shown.

To create a group:

1. In a project with no group, the path view says No axis group yet. Click New axis group, there or in the layout bar. Once the project has a group, click the + (New axis group) beside the list instead.

2. The Axis groups card opens over the path view with a new group added: Group 1 (or the next free number), using the project's first two axes as X and Y.

3. Give the group a Name, and choose its X axis, Y axis and, for a 3-D path, Z axis. Leave the Z axis at None (X-Y) for a flat path.

4. Click Done.

To change a group later, choose it in the list and click the pencil (Edit axis group). The card also has its own list of the project's groups, with Add group and Remove.

If the group can't be drawn yet, the card says why in red, for example Pick the group's Y axis. Each axis can only be used once in a group.

Axis groups are saved in the project, so adding or changing one counts as an unsaved change. Deleting an axis that a group uses empties that slot: the group stays, and the path view asks for an axis.

Note. Contours 2.0.7 and earlier open a project that has axis groups and run it normally, but ignore the groups. If you save the project from one of those versions, its axis groups are lost.

Reading the path

• Colour. By default the path is coloured by time: light blue at the start of the show, deepening to a strong blue at the end. The scale under the path reads Start to End.

• Time markers. A dot every second along the path. Dots close together mean slow movement; far apart, fast. The note under the path says how often, for example "A dot every 1 s".

• Start and end. A ring marks the start of the path and a square the end.

• Cursor dot. A magenta dot shows where the machine is at the time chart's cursor. It follows the cursor as you drag it, and while a show runs.

• Read-out. At the right under the path: the time at the cursor, each axis's position there and, when the axes share a unit, the speed along the path.

If there is nothing to draw yet, the path view says why, for example These axes have no take in this show yet.

Colour by speed. In the layout bar's Colour by section, choose Speed to colour the path by how fast the machine moves along it: slow green, through yellow, to fast red. The scale then reads Slow to Fast. This is the axes' speeds combined, which no single-axis chart shows, so it needs every axis in the group in the same unit. With mixed units, such as degrees and mm, Speed is greyed and the path is coloured by time; the (i) beside it explains why. Units are set on the Axes tab (see chapter 6).

Following the time chart's zoom. On the Shows tab, when you zoom the time chart or drag the zoom bar's window (see chapter 7), the path draws the stretch shown at full colour and fades the rest. Fit all on the zoom bar brings the whole path back.

Clicking the path. On the Shows tab, click a point on a 2-D path to move the time cursor, and the show's video, to that moment. Clicking the path never moves a motor. On the Test tab, or while recording, a click moves only the dot.

Tip. To send the motors to a point you found on the path, click the point, then click Run to cursor at the top of the Shows list.

Three-axis groups

A group with a Z axis is drawn in 3-D, with Z upright. In the 3-D view you see the whole path in perspective, and you can drag with the mouse to turn it. The layout bar's 3-D view list also offers three flat views: Top shows X and Y from above, Front shows X and Z, and Side shows Y and Z.

A view you have turned with the mouse stays as it is when you change a view option or zoom the time chart. To put it back, choose the same view again from the list. Each axis's Invert tick applies in 3-D too. Clicking a 3-D path doesn't move the cursor.

Path view options

Click the eye (View options) at the right-hand end of the layout bar. Its Path section, shown whenever the path view is, has:

• Start marker and End marker: show or hide the ring and the square.

• Time markers: show or hide the dots, and set how far apart they are in the Every box, from 0.1 s up to an hour. The dots change as you type. A value Contours can't use changes nothing, and the note under the box (0.1 s or more) turns red.

These choices are remembered between runs on this PC, not saved in the project, and apply wherever the path is shown. On the Shows tab the panel also has a Time chart section (see chapter 7). Ticking inside the panel doesn't close it; click anywhere outside it to close it.

Paths while recording, editing and testing

• Recording (see chapter 10). As a take is recorded, its path is drawn live over a faint copy of the group's existing path, with the dot on the newest point. The live path needs every axis in the group ticked for recording. After Save the path is drawn from the new take; after Cancel the earlier one comes back.

• Editing (see chapter 11). The path follows your changes in the point editor, whether you drag a point or type a value, within a fraction of a second. Cancel puts it back.

• Testing (see chapter 13). The layout bar is on the Test tab too. During a run the planned path is drawn faint, and the actual path, from the positions the motors report, is drawn live over it, as long as every axis in the group is in the run. With Data capture interval set to OFF the motors report nothing, so only the planned path is shown, and the path view says Data capture is off, so only the planned path is shown.

When the window is narrow

When the layout bar doesn't have room for everything, the sections on its right move into a ⋮ menu at its right-hand end: 3-D view first, then Colour by, then Axis group. They work the same from the menu. The eye always stays on the bar. The show's name sits in the middle of the bar while there is room, then moves aside and is shortened.