Making The Prototype Playable - Developing Games With Ruby - page 142

53 def pause ( id = :default )
54 @instances [ " #{ id } _l" ]. pause
55 @instances [ " #{ id } _r" ]. pause
56 end
57
58 def resume ( id = :default )
59 @instances [ " #{ id } _l" ]. resume
60 @instances [ " #{ id } _r" ]. resume
61 end
62
63 def stop
64 @instances . delete( " #{ id } _l" ) . stop
65 @instances . delete( " #{ id } _r" ) . stop
66 end
67
68 def volume_and_pan ( id , volume, pan)
69 if pan > 0
70 pan_l = 1 - pan * 2
71 pan_r = 1
72 else
73 pan_l = 1
74 pan_r = 1 + pan * 2
75 end
76 pan_l *= volume
77 pan_r *= volume
78 @instances [ " #{ id } _l" ]. volume = [ pan_l, 0.05]. max
79 @instances [ " #{ id } _r" ]. volume = [ pan_r, 0.05]. max
80 end
81 end

StereoSample manages stereo playback of sample instances, and to avoid memory
leaks, it has cleanup that scans all sample instances and removes samples that have
finished playing. For this removal to work, we need to place a call to

StereoSample.cleanup inside PlayState#update method.

To determine correct pan and volume, we will create some helper methods in Utils
module:

module Utils
HEARING_DISTANCE = 1000.0
# ...
def self . volume (object, camera)
return 1 if object == camera . target
distance = Utils . distance_between(