The Ten Commandments of Grids and Snaps

"For he had commanded the unclean spirit to come out of the man. Many times it had siezed him, and although he was guarded, bound by chains and shackles, he would snap the restraints and be driven by the demon back into deserted places." [Luke 8:29, Holman Christian Standard]

(It is a good idea to understand the Punch! basics before embarking on this document; see "The Ten Commandments of Punch! Basics".)

I.
 The Punch! grid/snap system has the following controls:
  • Grid visible toggle (on/off switch)
  • Snap to Grid toggle
  • Grid style (dots or lines)
  • Visible grid spacing, horizontal and vertical
  • Snap grid spacing, horizontal and vertical
  • In AS18 and AS3000, there are nine specialty snap tools
II.
 The use of the Grid Style, the Grid Visible and Snap to Grid controls function obviously as their names imply. The Grid Visible and Grid Style controls and the visible grid in general have no effect on how any other tools work.
III.
 Both of the grids (the visible and the snap) are drawn centered on the exact center of the chosen lot size. All position measurements are measured in positive or negative distance horizontally and vertically (as if on the monitor screen) from that center point. If the spacings of the two grids are the same, then they coincide exactly as well, and snapping will take place to the visible grid intersections. In normal (and default) use, the snap grid is spaced much finer than the visible grid, so it does not seem that things really do snap to the grid, but that is an incorrect observation.
IV.
 When the "Snap to Grid" is on, a line drawn on the lot as part of any object (alone, or the first of a connected series of segmented lines) will begin snapped to a grid intersection point. The length of the line drawn will be an even multiple of the horizontal snap amount. In addition, the angle of the line to the horizontal grid axis snaps to 5 degree increments. If the Shift key is held down while drawing the line, the end of the line will snap to a grid intersection regardless of the line length or angle of the line. If the Ctrl key is pressed and held while drawing a line, the line will only extend from it's first movement; it is not able to change direction. These same rules are in effect if one end of a line is seized by the mouse and changed.
V.
 If an entire line or entire object is selected and dragged with the mouse, the line will snap to locations which are even multiples of the horizontal and vertical snap sizes. If the Shift key is held down while dragging a line, the movement will be constrained to only the exact horizontal or vertical directions from the initial location, whichever is closer to the mouse point.
VI.
 Using the arrow keys to "nudge" an object, a line or a corner always moves it/them one snap size in the direction of the arrow key. The snap steps may be chosen as fine as one ten-thousandth of an inch (or to 1/32nd of an inch) and still be snapped in exact amounts, although this accuracy necessarily decreases as the range from the center increases - it decreases smoothly to about 1/1000th of an inch at 100" from the center point, approximately 1/100th at 1000" and so on. (Note that a 32nd of an inch is .03125", which requires 1/10,000th accuracy to handle exactly.) The entry spaces for the input of the snap size display rounded to .01 inches, but the actual value read in and stored is at least 6 decimal digits long.
VII.
 Default wall snap mode - If the user starts drawing a wall by clicking on an existing wall and moving outwards, the new wall will be constrained to be begin at the first wall (extended off it's ends if needbe) and be perpendicular to that wall.
VIII.
 There are nine specialty snap tools in AS18 and later Punch! programs which modify the default snap mode. Snap tools are applied to some pre-existing object; some tools are limited to walls, some to any object, some to an object's edge (or segment), and one to CAD (Detail tab) curves only. In general the tools work independently of whatever tool is making use of the snap. These snap tools all are one-shot tools; they revert back to No (default) Snap after use, unless the snap button is double-clicked, when it becomes a mode rather than just a momentary feature. When this is done the small ball in the button drawing turns red and the snap tool remains on until overridden. This on-mode is not saved in the project state, and so is forgotten between sessions.
IX.
 Due to the fact that these snaps interact with a great number of other Punch! GUI items, they are difficult to document in their entire roles. However, here is the top-level information for each:
  • No snap - turns other snap modes off. Use this if a snap mode was inadvertantly selected, and not desired, or to reset a doubly-clicked snap mode.
  • Snap to EndPoint (for walls) - after clicking this tool, walls drawn as suggested in Commandment 7 above will be constrained to start at the nearest endpoint of the original wall. This wall will not be constrained to the snap grid but is subject to the angle snap. As always, the endpoint will leave the wall an integral horizontal snap length, unless the Shift key is used to constrain the endpoint to the grid, ignoring the length and angle snap.
  • Snap to Segment Center (for walls) - This snap starts the new wall in the center of the original; otherwise it has the same action as the Endpoint snap.
  • Snap to Object Center (for objects) - Turn this snap on, click on a tool, then click to startt drawing with this tool on a part of the outline of some object, and the start origin will be snapped to the geometric center of the object started on.
  • Snap to Object Corner (for objects) - Just like the Object Center snap, except that it snaps to the nearest object corner to start.
  • Snap to Intersection (presumably for objects) - I cannot make this tool operate as advertized. It snaps to the nearest grid intersection and allows a wall to be struck that can cross other walls, which is normally not done - walls normally end where they intersect an existing wall in their path.
  • Snap to perpendicular (for CAD lines) - draw a curved figure on the Detail tab, click on the straight line tool, and this snap, and then click and drag from the curve outwards or inwards. The line will be perpendicular to the curve at the point where it touches the curve, and can be dragged around the curve. Beware dragging it off the end of an open curve; it will loose it's way and not be able to find it back again. It will also work on straight-edged objects, but only on the one face it starts on.
  • Snap to Segment Offset (for any object segment) -
  • Snap to Segment (for any object segment) - Curiously, this snap is undocumented in Punch! (AS18, 3000 or MLP), except in the Layout Manager.

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This page last updated on Sun May 14 2006
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