0.
I.
The World Cube - The Punch! world consists of a cube of brown "dirt" topped with the grass upper surface. The surface is flat and defines the Zero Plane - the universal elevation reference (see the Ten Commandments of the Vertical). Later, when the terrain has been changed, it moves away from the Zero Plane, which is itself unmovable. You can see the grid in ClearView. When you cut a hole in the terrain and look inside, all you'll see is the inside of the brown cube, which can be thought of as the brown side of the "hole" you dug in the terrain. Unfortunately this allusion is sometimes spoiled by a glimpse of a basement extending below the ground, but it works well in the absence of a 3D analog to a solid dirt mass.
II.
Terrain Grid - The top surface ("terrain") is divided up by a default 36 inch grid system, originating in the northwest corner of the terrain. The grid size may be varied in the TD from 12" to 720". On a maximal lot (1000'x1000') that makes 333x333 grid squares, or 110,889 grid intersections ("vertexes"). At the minimal grid size there are nearly a million vertices. Only at these intersections may the vertical elevation at that point be defined; The points in between are interpolated from these defined points. The grid system may be viewed directly by using ClearView; in addition, if the size of your lot is evenly divisible by 6 feet in both directions, then a 36"X36" plan grid will coincide with this terrain grid, making it visible on the plan if needed. (The terrain grid originates at the upper left corner of the lot; the plan grid originates at the lot center, so they only coincide when the lot size is a multiple of 6' in both directions as recommended.)
III.
The Contour Tool - The TD has only a single basic tool to set the terrain: the contour. All the tool buttons in the TD all draw contours in one shape or another. A contour is a continuous line which defines the places which all have the same elevations. Common sense says that you can always find a path along the ground which neither rises nor falls, but stays at the same level, ragardless of how hilly or "bad land" a geography may be, disregarding things like caves and overhangs. These are contours. Contours also can end in one direction (when for example a ridge line ends), they can branch and even loop. What they can never do is cross except at the afre-mentioned cave entrances and cliff overhangs. There is no rule in the TD that prevents two contours of different heights from meeting or crossing, but the result is unstable terrain. In nature, contours close together indicate a steep slope; far apart indicates a relatively flat terrain. "V" shapes in contours indicate where gullies or ridges occur in flatter, sloping ground. This is in contrast to the similar berms that Punch! used before the TD; they could overlap, and the result was the adding together of berms. Contours are not additive; their values are absolute elevations.
If you need more help with the concept of contours, any topographical map will display real examples. In addition, visit these sites:
- http://academic.brooklyn.cuny.edu/geology/leveson/core/linksa/elevation.html
- http://www.cis.ksu.edu/~dha5446/topoweb/guide.html
- http://mac.usgs.gov/isb/pubs/booklets/symbols/reading.html
- Instructions on how to draw contours: http://squall.sfsu.edu/courses/metr302/F96/handouts/contouring.html
In addition, I'm adding this simple illustration which shows very simply how to set up terrain for a walk-out basement. The house consists of a set of walls on the second floor, and a similar, but smaller set on the first floor. We want the second floor to be at terrain level in the front, but the first floor at terrain level in the back. The simplest possible terrain to do this is shown on the right.
Note the problems - the tunnel through the building behind the first floor, and "Mt. Vesuvius" in the background. The former is taken care of by adding walls to the first floor to fill in; these would be foundation walls in the real building. I added them using the interior wall tool since they aren't really exterior walls in the Punch! sense (see The Ten Commandments of Walls), and I colored them red and didn't quite close the gap so that The Gentle User can see how they were done. The mountain in the distance, which is only about 6' high, is caused by bringing two different elevations together but leaving a gap where the elevation is indeterminate (an example of the instability I mentioned earlier). This is fixed in the second model by dragging the contour all the way to the edge of the drawing area.
IV.
Not Using Real Elevations - In the old tools it was understood that the zero plane should be equated to some convenient elevation (like the basement floor's elevation). Due to an unfortunate choice in words, in the TD doc, many have been tempted to try to create contours with real elevations. I live in Denver "The Mile High City", Colorado, and doing that here would mean that I would have a basement elevation of, perhaps, 5327' (63924"), and the next floor up might be at 64032". Doing this, while theoretically possible, is fraught with danger and confusion. The better way is, like before, to call a convenient elevation the Zero Plane and measure everything relative to it (including, most particularly, the contour elevations set in the TD).
V.
Rules about Contours - In the TD it is not necessary to draw the contours to meet in circuits, the way it was for the berm tool. Generally they are drawn from one edge of the Punch! lot to some other, or they form loops within the lot. In some cases it is possible that they will form a line that simply ends somewhere on the lot, but this should be rare. Remember that in any area that you haven't defined contours surrounding a point usually at the edge of the lot) the elevation model can get unstable, resulting in a mathematical roughness. Some people have drawn a closed circuit around a house and set the contour level, and when viewed the terrain is flat - this is because no other level has been defined anywhere within, so the model is assumed to be the same as the drawn contour all over. Contours need to contrast to show relief.
VI.
Contours Translate to the Grid - The TD constructs a topography which matches the contours. There are, of course, an infinite number of ways to do that, as the contours only "staple down" the lines along which they run. One solution would be a linear interpolation of space between the contours, akin to the way the berms in the older model worked. The TD seems to have a more complex way of building up the terrain "sheet". Unfortunately, it seems to accentuate the contours, appearing to sag a bit between them. When building up a hill, a "wedding cake" appearance seems to be inevitable. See the graphic which introduces this topic on the Ten Commandments page.
VII.
Float on Topography - "Float on topography" is a term meaning that the elevation of an object is determined by computing the terrain elevation at each point along its length and applying it to the object at those points - this applies to plants, fences, railings, and some other objects, and even to some, like decks, stairs and floors for which it is undesirable for use. It is "turned off" by applying some constant elevation instead.
VIII.
Cutting Holes in the Terrain - Exterior wallsets (see the Ten Commandments of Walls) and the excavation tool can cut holes in the terrain. This is done by making the terrain over the region transparent, not by actually eradicating it; this has effects on various Punch! actions, such as applying a texture while pointing through such a hole (see The Ten Commandments of Punch! Problems, article III). The excavator has an additional "floor" drawn at a positive or negative height from the terrain elevation of the point where the excavation drawing was started, shaped according to the plan shape of the cutout and constructed flat.
IX.
Fills and Paths - Fills and paths are surfaces drawn 2-3" inches above the terrain as measured at the handles of the fill or path. Since it is not measured at *all* of the points the fill covers (just at the handles), a bumpy terrain can poke through fill or a path. Increasing the handles will make the fill more compliant to bumpy terrain, but, of course, handles cannot cover the whole surface (they are around the edge of a fill, and down the center of a path), so bumpy terrain can defeat fills.
X.
Can't Use a Berm Anymore - From the older terrain doc: "A positive berm over the entire surface of the world has the net effect of raising or lowering the Zero Plane in all locations, so that can be used to set the Zero Plane to some useful place, like the top of the basement floor in a house. Then all elevations are positive and have a basis in reality, rather then being arbitrary." This is a corollary of the fact that berms were additive in the old system. Unfortunately, there is no equivalent dodge in the TD; the only way to raise of lower the entire topography is to change all of the contour levels by a fixed amount. While not as convenient as in the earlier terrain model, it still is better then the alternative: changing the elevation of all the objects in a house.
XI.
Scale Contours - The options box in the TD has an unexplained option. The checkbox labeled "Scale Contours" is meant to change the scaling of the contours if the lot size is changed, rather than just leaving them limited within the former boundaries of the older plot size.
XII.
Trace - The TD has a trace option, just as the main Punch! program does. The idea is to allow the user to scan in a terrain plat (from a topo map, perhaps, or a surveyors contour map) and allow it to "underlay" the drawing surface while drawing, so that the contour tool can be used to approximate the known contours. That makes it easy to "digitize" a paper contour map, the most common contour data source. But the tool is a bit trickey. Note that this is the same feature that is used in the main Punch! floorplan trace, so the following is applicable to both.
First of all, the paper map has to be scanned to create a graphic file. The file format, up until version 8, had to be a .bmp file, but after that point it may be any of a number of different formats: .bmp, .png, .jpg, .gif, .psd, .tga, or .emf/.wmf. The scanned map needs one particular thing (besides the contours, of course) - it needs a definite length displayed on the map. This might be the known distance between two landmarks on the map, a surveyor's distance, or a knwn edge length of the map image itself. Once the map has been scanned into a graphics format, select Design->Load Topography Trace Image..., and browse to the scanned in graphic file. As soon as it is identified, The TD will display it on the TD workspace.
The file will always be displayed centered in the workarea. Therefore it is better to do a trace before other TD data is gathered, so the other data can be arranged around the trace, and not try to do the reverse. The fact that it is centered has one important ramification: the same is true for the Drawing Trace in the main Punch! program, so if the two traces used are registered with each other or are indeed the same file, then the two will automatically match up, as long as the scaling process following is done the same in both cases.
Now that the image is on the screen, grab the dimension tool on the left margin and draw a dimension arrow along the known distance or between the two landmarks on the map. The dimension will tell you how far Punch! thinks the two known locations are apart. It is only by chance that that would be the correct distance on the map. Compute the following correction factor:
factor = 100 x (known distance / dimension distance)
making sure, of course, that the same units are used for the two distance values (feet, inches or meters, but only one of them). Choose the menu selection Design->Resize Topography Trace Image..., and input the factor into both the horizontal and vertical resize percentage boxes, and click OK. Use the dimension again to see if it and the known distance now agree; if not, redo the calculation and try again.
The third trace menu selection is Topography Trace Image Visible. Use this to turn off the trace after it is fulfilled its destiny.
