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Updated to reflect current scenery progress.

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curt 1999-03-21 15:12:51 +00:00
parent 885df202f7
commit 0f1c53a5bc
1 changed files with 56 additions and 21 deletions
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77
SceneGeneration/SceneryGeneration.tex
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@ -337,14 +337,14 @@ This tools inputs an ascii specification of the airports of the world
that looks like the following:
\begin{verbatim}
A KORD 41.979595 -087.904464 668 CYY Chicago O Hare International
R 04L 41.989606 -087.905138 039.39 7500 150 AHYN NNNLYN NNNNNY
R 04R 41.961618 -087.889594 041.40 8071 150 AHYN YNNNNY YNNNNY
R 09L 41.983954 -087.903705 089.70 7967 150 AHYN YNNNNY YNNNNY
R 09R 41.969040 -087.902380 089.88 10141 150 AHYN YNNNNY YNNNNY
R 14L 41.991918 -087.903546 140.10 10003 150 AHYN YNNBYN YNNNNY
R 14R 41.976778 -087.917774 140.08 13000 200 AHYN YNNBYN YNNNNY
R 18 41.990086 -087.900410 180.00 5341 150 AMNN NNNNNN NNNNNN
A KORD 41.979595 -087.904464 668 CCY Chicago O Hare International
R 04L 41.989606 -087.905138 039.39 7500 150 AHYN NNNL 0 0 NNNO 0 0
R 04R 41.961618 -087.889594 041.40 8071 150 AHYN YNNO 0 0 YNNO 0 0
R 09L 41.983954 -087.903705 089.70 7967 150 AHYN YNNO 0 0 YNNO 0 0
R 09R 41.969040 -087.902380 089.88 10141 150 AHYN YNNO 0 0 YNNO 0 0
R 14L 41.991918 -087.903546 140.10 10003 150 AHYN YNNC 0 0 YNNO 0 0
R 14R 41.976778 -087.917774 140.08 13000 200 AHYN YNNC 0 0 YNNO 0 0
R 18 41.990086 -087.900410 180.00 5341 150 AMNN NNNN 0 0 NNNN 0 0
\end{verbatim}
For each airport, a bounding polygon is generated, and written as a
@ -394,6 +394,9 @@ Dump the raw data into the appropriate tile areas in the work space.
This includes height data (DEM, airport) and polygon data (airport,
hydro-data, land use data, etc.)
For each tile create a fitted set of ``important height'' points from
the original regular grid of data.
For each tile, run the generic clipper on each polygon in order from
highest to lowest incrementally building an accumulation ``super''
polygon that comprises a union of all polygons we've processed so far
@ -403,21 +406,50 @@ shape of the polygon. This is the scheme for eliminating overlapping
features on a priority basis.
For each polygon on a tile we must determine a point inside. We need
this for the triangulation step.
this for the triangulation step so we can assign a regional attribute
to all triangles inside a polygon.
For each polygon, triangulate all the height fields in the tile.
Using the triangle library we can feed in all the polygon outlines
with the corresponding interior points. We can tell the triangulator
to start at every point except for the one we are working on and eat
away all the triangles until a polygon border is encountered. This
leaves us with the triangulation of each polygon.
Run the delauney triangulator for the tile. The triangulator code is
very powerful and feature rich, but also very obfuscated to use. It
is very robust and fast, but suffers a bit on the usability continuum.
Now we have a pile of height data and the triangulation for each
polygon. However, some of these hieght fields must be enforced
(airports) and some of this can be adjusted (base terrain). We might
also want to think about ensuring lakes are level, and rivers don't
run up and down hills. Anyways, with a flurry of handwaving, we have
adjusted all the heights.
In preparation for the triangulation step we need to create the
following items:
\begin{itemize}
\item A list of all unique vertices (nodes) in this tile, including
the corners
\item A list of all the unique segments (edges of the polygons) in no
particular order. The triangulator doesn't really care how the
polygons connect together, it just cares about boundary edges.
\item A list of ``holes'' (if any) to cut out of the tile. If an
airport overlaps multiple tiles we assign it one tile and leave a
hole in remaining tiles. A hole is specified by a single point.
When the triangulation step is finished, the triangulator will start
at each hole point and recursively eat away all neighboring
triangles until it encounters an edge.
\item A list of regions with region attributes. These are specified
much the same way as holes. After the triangulation step is
finished, regional attributes are assigned. The procedure is
identical to cutting out a hole except that instead of removing a
triangle it is simply assigned the attribute for that region.
\end{itemize}
The result of the triangulation step is a list of triangles for the
tile with each triangle assigned an attribute representing the polygon
it lives inside.
Now we have a pile of triangles. We are heading in the right
direction! However, no we need to go through and assign the proper
height to each of the verticies of the triangles. We must be aware of
certain constraints. Airport elevations should have the highest
priority, followed by the DEM elevations. We will also want to impose
additional constraints such as ensuring lakes are level and rivers
don't run up hill. Anyways, with a flurry of handwaving, we have now
adjusted all the heights. :-)
The next thing we have to worry about is making sure each tile meshes
exactly with all it's neighbors. We do this by spliting the tile up
@ -517,6 +549,9 @@ Generates the width of a 1/8 x 1/8 degree tile at various latitudes.
%------------------------------------------------------------------------
% $Log$
% Revision 1.4 1999/03/21 15:12:51 curt
% Updated to reflect current scenery progress.
%
% Revision 1.3 1999/03/13 21:42:37 curt
% Updated to match current scenery generation tools progress.
%