§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 "carrying capacity". This is a maximum number of contents:
The carrying 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
![]() | Start of Chapter 10: Physics: Substances, Ropes, Energy and Weight |
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![]() | Onward to §10.6. Ropes |
Suppose we have marbles that roll downhill across our map, in a life-size version of one of those marble-chute toys. We might now want to keep track of both compass relationships and which-room-slopes-into-which, so we make a new relation:
And let's say we want the player to be allowed to slide, too, since that would be much more fun than just watching the marbles go:
Now a rule to control what happens to all our sliding and rolling objects:
Since the Ski-jump overlooks the Landing Bowl, the marble will be able to fly through the air to its destination, even though there is no map connection to allow the player to cross. We might want to let the player make it across this barrier also, so:
Because overlooking is various-to-various, we could include that element popular in marble chute toys, the splitter:
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Suppose we have marbles that roll downhill across our map, in a life-size version of one of those marble-chute toys. We might now want to keep track of both compass relationships and which-room-slopes-into-which, so we make a new relation:
And let's say we want the player to be allowed to slide, too, since that would be much more fun than just watching the marbles go:
Now a rule to control what happens to all our sliding and rolling objects:
Since the Ski-jump overlooks the Landing Bowl, the marble will be able to fly through the air to its destination, even though there is no map connection to allow the player to cross. We might want to let the player make it across this barrier also, so:
Because overlooking is various-to-various, we could include that element popular in marble chute toys, the splitter:
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