Main Goal

• Development of an application that allows flying virtually over El Hierro Island (Canary Islands), showing the building structures of a hydroelectric power station that is in construction.

Input data: Aerial photos

• 66 TIFF images of 2.500 x 2.500 pixels

• 1:5.000 scale of the island surface (1 m2 per pixel).

Input data: Height map

• Rectangular grid with data value each 10 meters.

3.000 points

2.500 points

Input data: Building and structures design

• Planes and designs of buildings and structures of the power station (including one new harbour).

Development tool used

• Free and portable game development kit

• It supports funcionality to:

– handle large poligonal meshes, – moving around a 3D world, – show atmospheric and light effects to make the scene more realistic.

LOD Algorithm

• The whole island is covered by a triangle mesh, created from the input height map.

• This mesh is composed of 66 simple meshes of 250x250 triangles (approx. 62 thousand).

• Total for the island is more than 4 million of triangles.

• A LOD (Level Of Detail) algorithm is used to simplify meshes too far from viewer.

Texture mapping2.500 x 2.500

1 pixel = 1m2

2.048 x 2.048

1 pixel = 1.5 m2

• Aerial photos are texture mapped on every mesh.

• Every texture is re-dimensioned to 2.048 x 2.048 (power of 2)

Mipmapping

• We use an special file format to store the mipmap data on every image.

• A mipmapping algorithm decides the detail level of each texture according to the distance to viewer.

2.048 x 2.048

1.024 x 1.024

512 x 512

256 x 256

Generation of the sea

• Represented by a single large polygon, mapped with a synthetic sea photo.

• Next, every aerial photo that include sea areas was processed to blur the real sea.

• This allows to avoid the visual discontinuity between real and sinthetic sea.

Sky representation

• The sky is represented by a semisphere.

• A synthetic sky with clouds was generated and texture mapped on the semisphere.

• In areas close to horizon, the sky was blurred to achieve a more realistic effect.

Buildings design

• Every structure of the power station was designed with a 3D modeller software and located in the exact position over the island.

Natural structure design

• Some natural structures was designed.

• It achieves a 3D effect when the camera approach, much better that using just the 2D photo viewed from the top.

Interface design

R

Automatic flights between two points

A

Current viewdirection

B

Final viewdirection

2. Straight line

3. Final rotation

1. Initial rotation

• Between a point A with an initial orientation, to a point B with a final orientation.

Collision detection

y

x, z

Height ofviewer

Height of terrainunder viewerposition

• We have to avoid that viewer crosses the terrain

Visualization of names

y

x, zPopulation

d

View direction

View up vector

• Visualization of names of populations and interest places over their exact location on the island.

Information panel visualization

y

x, zInterest place

d

View direction

• Generation of information panels, with photo and text.

• Application must show the suitable panel in every moment, depending on the place flown over.