10.5. Volume, Height, Weight

| Chapter 10: Physics: Substances, Ropes, Energy and Weight |

| 10.5. Volume, Height, Weight

What should fit into what? Inform has basically three sizes: small, person-sized, and room-sized. The difference between "small" and "person-sized" doesn't appear much, but it's the difference between an ordinary container and an enterable container; the fact that a person cannot get inside an ordinary container is one of the few size-related rules built into Inform. It will not object to, say, a fishing rod being put inside a matchbox.

Inform does have one built-in measure of the size of a container: its "capacity". This is a maximum number of contents:

> The capacity of the rucksack is 3.

This of course allows three anvils, while forbidding four postage stamps. To do better, we need units of measurement, and Dimensions demonstrates setting these up. The Speed of Thought, meanwhile, ventures into the area of unit conversion: having multiple types of unit and being able to express them to the player, or parse these in the player's input.

To be fully realistic in what will fit into what, we need sophisticated three-dimensional models of shapes, both of the items being carried and of the free space remaining inside containers. Depth elegantly simplifies this by approximating items as cuboids, with a given width, length and height: these multiply to give a volume. To fit in a container, a new item's volume must not exceed the volume remaining inside the container, and in addition its three dimensions must also fit in one of the possible arrangements at right angles to the sides. (So this system would indeed prevent a 1x1x100 fishing rod from being put inside a 5x2x1 matchbox, but would also prevent a 12x1x1 pencil from being put into a 10x10x1 box, because it would need to be turned diagonally to fit.)

Lead Cuts Paper provides a different constraint: here we do not let light-weight containers hold heavy objects.

Weight comes in a different way into Swerve left? Swerve right? Or think about it and die?, which exploits up/down map connections to work out which way gravity would take a rolling marble.

See Liquids for containers with liquid capacity

247
| Example Dimensions This example draws together the previous snippets into a working implementation of the weighbridge. |
WI

259
| Example The Speed of Thought Describing scientifically-measured objects in units more familiar to the casual audience. |
WI

257
| Example Depth Receptacles that calculate internal volume and the amount of room available, and cannot be overfilled. |
WI

248
| Example Lead Cuts Paper To give every container a breaking strain, that is, a maximum weight of contents which it can bear - so that to put the lead pig into a paper bag invites disaster. |
WI

The following uses a few features which will not be explained until later chapters, but it shows the kind of "realism" rules which could be introduced using weights. Not entirely realistic: we do not bother to rupture containers out of the player's sight. "Lead Cuts Paper" A weight is a kind of value. 10kg specifies a weight. Everything has a weight. A thing usually has weight 1kg. A container has a weight called breaking strain. The breaking strain of a container is usually 50kg. Definition: A container is bursting if the total weight of things in it is greater than its breaking strain. A lead pig, a feather, a silver coin and a paper bag are in a room called the Metallurgy Workshop. The paper bag is a container with breaking strain 2kg. The lead pig has weight 50kg. Every turn when a container (called the sack) held by someone visible (called the chump) is bursting: say "[The sack] splits and breaks under the weight! [if the player is the chump]You discard[otherwise][The chump] discards[end if] its ruined remains, looking miserably down at [the list of things in the sack] on the floor."; now all of the things in the sack are in the location; remove the sack from play. Test me with "get bag / get feather / put feather in bag / get pig / put pig in bag / look".

231
| Example Swerve left? Swerve right? Or think about it and die? Building a marble chute track in which a dropped marble will automatically roll downhill. |
WI

Previous | Contents | Next