1scene_gap(3) Allegro manual scene_gap(3)
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6 scene_gap - Number controlling the scene z-sorting algorithm behaviour.
7 Allegro game programming library.
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10 #include <allegro.h>
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13 extern float scene_gap;
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16 This number (default value = 100.0) controls the behaviour of the z-
17 sorting algorithm. When an edge is very close to another's polygon
18 plane, there is an interval of uncertainty in which you cannot tell
19 which object is visible (which z is smaller). This is due to cumulative
20 numerical errors for edges that have undergone a lot of transformations
21 and interpolations.
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23 The default value means that if the 1/z values (in projected space)
24 differ by only 1/100 (one percent), they are considered to be equal and
25 the x-slopes of the planes are used to find out which plane is getting
26 closer when we move to the right.
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28 Larger values means narrower margins, and increasing the chance of
29 missing true adjacent edges/planes. Smaller values means larger mar‐
30 gins, and increasing the chance of mistaking close polygons for adja‐
31 cent ones. The value of 100 is close to the optimum. However, the
32 optimum shifts slightly with resolution, and may be application-depen‐
33 dent. It is here for you to fine-tune.
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39 create_scene(3), clear_scene(3), destroy_scene(3), render_scene(3),
40 scene_polygon3d(3)
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44Allegro version 4.4.3 scene_gap(3)