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<title>DM4 §8: Places and scenery</title>
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<h2>§8 Places and scenery</h2>
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<p class="normal"><span class="atleft"><img src="dm4-116_1.jpg" alt=""></span>
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In this longer chapter the model world of an Inform game will be
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explored and examples will gradually complete the ‘Ruins’
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begun in Chapter II. So far, ‘Ruins’ contains just a
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location of rainforest together with some rules about photography.
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The immediate need is for a more substantial map, beginning with a
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sunken chamber. Like the Forest, this too has <code>light</code>, however dim. If
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it didn't, the player would never see it: in Inform's world darkness
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prevails unless the designer provides some kind of lamp or, as in this
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case, ambient light.</p>
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<p class="lynxonly"></p>
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Object Square_Chamber "Square Chamber"
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with name 'lintelled' 'lintel' 'lintels' 'east' 'south' 'doorways',
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"A sunken, gloomy stone chamber, ten yards across. A shaft
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of sunlight cuts in from the steps above, giving the
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chamber a diffuse light, but in the shadows low lintelled
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doorways to east and south lead into the deeper darkness
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<p class="normal">This room has a <code>name</code> property even
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though rooms are not usually referred to by players. The nouns given
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are words which Inform knows “you don't need to refer to”,
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and it's a convention of the genre that the designer should signpost
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the game in this way. For the game to talk about something and later
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deny all knowledge – “I can't see any such thing”
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– is not merely rude but harmful to the player's illusion of
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holding a conversation about a real world. Better to parry with:</p>
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<p class="output">><tt>examine lintel</tt><br><a id="p117" name="p117"></a>
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That's not something you need to refer to in the course of this game.</p>
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<p class="dotbreak">� � � � �</p>
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<p class="normal">Not all of the Square Chamber's décor is so
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<p class="lynxonly"></p>
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Object -> "carved inscriptions"
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with name 'carved' 'inscriptions' 'carvings' 'marks' 'markings'
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'symbols' 'moving' 'scuttling' 'crowd' 'of',
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"Carved inscriptions crowd the walls, floor and ceiling.",
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"Each time you look at the carvings closely, they seem
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to be still. But you have the uneasy feeling when you
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look away that they're scuttling, moving about. Two
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glyphs are prominent: Arrow and Circle.",
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has static pluralname;
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<p class="normal">The <code>static</code> attribute means that the inscriptions
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can't be taken or moved. As we went out of our way to describe a shaft
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of sunlight, we'll include that as well:</p>
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<p class="lynxonly"></p>
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Object -> sunlight "shaft of sunlight"
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with name 'shaft' 'of' 'sunlight' 'sun' 'light' 'beam' 'sunbeam'
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'ray' 'rays' 'sun^s' 'sunlit' 'air' 'motes' 'dust',
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"Motes of dust glimmer in the shaft of sunlit air, so
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that it seems almost solid.",
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<p class="normal">The <code>^</code> symbol in <code>"sun^s"</code>
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means an apostrophe, so the word is “sun's”. This
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object has been given the constant name <code>sunlight</code> because
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other parts of the ‘Ruins’ source code will need to refer
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to it later on. Being <code>scenery</code> means that the object is
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not only static but also not described by the game unless actually
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examined by the player. A perfectionist might add a <code>before</code>
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<p class="lynxonly"></p>
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default: "It's only an insubstantial shaft of sunlight.";
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<p class="normal">so that the player can look at or through the sunlight,
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but any other request involving them will be turned down. Note that
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a <code>default</code> rule, if given, means “any action except
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those already mentioned”.</p>
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<a id="p118" name="p118"></a>
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<p class="aside"><span class="warning">▲</span>
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Objects having <code>scenery</code> are assumed to be mentioned in
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the description text of the room, just as the “shaft of sunlight”
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is mentioned in that of the Square Chamber. Giving an object <code>concealed</code>
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marks it as something which is present to a player who knows about it,
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but hidden from the casual eye. It will not be cited in lists of objects
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present in the room, and “take all” will not take it, but
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“take secret dossier”, or whatever, will work. (Designers
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seldom need <code>concealed</code>, but the library uses it all the
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time, because the player-object is concealed.)</p>
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<p class="dotbreak">� � � � �</p>
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<p class="normal">Some scenery must spread across several rooms. The
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‘Ruins’, for instance, are misty, and although we <em>could</em>
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design them with a different “mist” object in every misty
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location, this would become tiresome. In ‘Advent’,
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for instance, a stream runs through seven locations, while mist which
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(we are told) is “frequently a sign of a deep pit leading down
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to water” can be found in ten different caves. Here is a
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<p class="lynxonly"></p>
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Object low_mist "low mist"
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with name 'low' 'swirling' 'mist',
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description "The mist has an aroma reminiscent of tortilla.",
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found_in Square_Chamber Forest,
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Smell: <<Examine self>>;
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default: "The mist is too insubstantial.";
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<p class="normal">The <code>found_in</code> property gives a list
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of places in which the mist is found: so far, just the Square Chamber
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<p class="aside"><span class="warning">▲</span>
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This allows for up to 32 misty locations. If scenery has to be visible
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even more widely than that, or if it has to change with circumstances
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(for instance, if the mist drifts) then it is simpler to give a routine
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instead of a list. This can look at the current location and say whether
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or not the object should be present, as in the following example from
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a game taking place at night:</p>
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<p class="lynxonly"></p>
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Object Procyon "Procyon",
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with name 'procyon' 'alpha' 'canis' 'minoris' 'star',
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description "A double-star eleven light years distant.",
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return (location ofclass OutsideRoom);
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<a id="p119" name="p119"></a>
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<p class="aside"><code>found_in</code> is only consulted when the player's
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location changes, and works by moving objects around to give the illusion
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that they are in several places at once: thus, if the player walks from
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a dark field to a hilltop, Procyon will be moved ahead to the hilltop
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just in advance of the player's move. This illusion is good enough for
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most practical purposes, but sometimes needs a little extra work to maintain,
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for instance if the sky must suddenly cloud over, concealing the stars.
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Since it often happens that an object must be removed from all the
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places in which it would otherwise appear, an attribute called
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<code>absent</code> is provided which overrides <code>found_in</code>
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and declares that the object is found nowhere. Whatever change is made
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to <code>found_in</code>, or in giving or removing <code>absent</code>,
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the Inform library needs also to be notified that changes have taken
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place. For instance, if you need to occult Procyon behind the moon
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for a while, then:</p>
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<p class="lynxonly"></p>
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<pre class="code">give Procyon absent; MoveFloatingObjects();</pre>
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<p class="aside">The library routine <code>MoveFloatingObjects</code>
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keeps the books straight after a change of state of <code>found_in</code>
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or <code>absent</code>.</p>
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<p class="dotbreak">� � � � �</p>
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<p class="normal">Whereas Procyon is entirely visual, some scenery
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items may afflict the other four senses. In ‘Ruins’,
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the <code>Forest</code> contains the rule:</p>
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<p class="lynxonly"></p>
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Listen: "Howler monkeys, bats, parrots, macaw.";
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<p class="normal">Besides which, we have already said that the mist
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smells of tortilla, which means that if the player types “smell”
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in a place where the mist is, there should clearly be some reaction.
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For this, a <code>react_before</code> rule attached to the mist is
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<p class="lynxonly"></p>
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Smell: if (noun == nothing) <<Smell self>>;
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<p class="normal">This is called a “react” rule because
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the mist is reacting to the fact that a <code>Smell</code> action is
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taking place nearby. <code>noun</code> is compared with <code>nothing</code>
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to see if the player has indeed just typed “smell” and
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not, say, “smell crocus”. Thus, when the action
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<code>Smell</code> takes place near the mist, it is converted into
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<code>Smell low_mist</code>, whereas the action <code>Smell
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crocus</code> would be left alone.
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<p class="indent">The five senses all have actions in Inform:
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<code>Look</code>, <code>Listen</code>, <code>Smell</code>,
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<code>Taste</code> and <code>Touch</code>. Of these, <code>Look</code>
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never has a noun attached (because <code>Examine</code>,
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<code>LookUnder</code> and <code>Search</code> are provided for
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close-up views), <code>Smell</code> and <code>Listen</code> may or
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may not have while <code>Taste</code> and <code>Touch</code> always
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<a id="p120" name="p120"></a>
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<p class="aside"><span class="warning"><b>•</b>
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<b><a href="sa6.html#ans6">EXERCISE 6</a></b></span><br>
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(Cf. ‘Spellbreaker’.) Make an orange cloud descend on
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the player, which can't be seen through or walked out of.</p>
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<p class="dotbreak">� � � � �</p>
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<p class="normal">Rooms also react to actions that might occur in them
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and have their own <code>before</code> and <code>after</code> rules.
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Here's one for the Square Chamber:</p>
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<p class="lynxonly"></p>
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if (noun == eggsac && second == sunlight) {
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remove eggsac; move stone_key to self;
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"You drop the eggsac into the glare of the shaft of
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sunlight. It bubbles obscenely, distends and then
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bursts into a hundred tiny insects which run in all
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directions into the darkness. Only spatters of slime
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and a curious yellow-stone key remain on the chamber
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<p class="normal">(The variables <code>noun</code> and <code>second</code>
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hold the first and second nouns supplied with an action.) As it happens
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this rule could as easily have been part of the definition of the eggsac
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or the sunlight, but <code>before</code> and <code>after</code> rules
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for rooms are invaluable to code up geographical oddities.</p>
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<p class="aside"><span class="warning"><b>•</b>
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<b><a href="sa6.html#ans7">EXERCISE 7</a></b></span><br>
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Create a room for ‘Ruins’ called the Wormcast, which has
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the oddity that anything dropped there ends up back in the Square Chamber.</p>
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<p class="aside"><span class="warning">▲</span>
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Sometimes the room may be a different one after the action has taken
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place. The <code>Go</code> action, for instance, is offered to the
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<code>before</code> routine of the room which is being left, and
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the <code>after</code> routine of the room being arrived in. For example:</p>
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<p class="lynxonly"></p>
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Go: if (noun == w_obj)
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print "You feel an overwhelming sense of relief.^";
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<p class="aside">will print the message when its room is entered from
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the “west" direction. Note that this routine returns <code>false</code>,
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in the absence of any code telling it to do otherwise, which means
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that the usual game rules resume after the printing of the message.</p>
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<a id="p121" name="p121"></a>
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<p class="aside"><span class="warning"><b>•</b>
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<b>REFERENCES</b></span><br>
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‘A Scenic View’ by Richard Barnett demonstrates a system
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for providing examinable scenery much more concisely (without defining
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so many objects).
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<span class="warning"><b>•</b></span><code>found_in</code>
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can allow a single object to represent many different but similar objects
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across a game, and a good example is found in Martin Braun's <tt>"elevator.inf"</tt>
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example game, where every floor of a building has an up-arrow and a
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down-arrow button to summon an elevator.</p>
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