Android Invaders: The Grand Finale - Beginning Android Games - page 586

Figure 12-8. The ship model in Wings3D (ship.obj) and its texture (ship.png, 256×256 pixels)
The crucial thing is that the ship in Figure 12-8 has roughly the “radius� outlined in the previous
section. We don't need to scale anything or transform sizes and positions from one coordinate
system to the other. The ship's model is defined with the same units as its bounding sphere!
Figure 12-9 shows the invader model and its texture.
Figure 12-9. The invader model (invader.obj) and its texture (invader.png, 256×256 pixels)
The invader model follows the same principles as the ship model. We have one OBJ file storing
the vertex positions, texture coordinates, normals and faces, and a texture image.
The shield blocks and shots are modeled as cubes and are stored in the files shield.obj and
shot.obj . Although they have texture coordinates assigned, we don't actually use texture
mapping when rendering them. We just draw them as (translucent) objects with a specific color
(blue in the case of the shield blocks, yellow for the shots).
Finally, we have our explosions (see Figure 12-3 again). How do we model those? We don't. We
do what we did in 2D and simply draw a rectangle with a proper z position in our 3D world, texture
mapping it with a frame from a texture image containing an explosion animation. It's the same
principle we used for the animated objects in Super Jumper. The only difference is that we draw
the rectangle at a z position less than 0 (wherever the exploding object is located). We can even
abuse the SpriteBatcher class to do this. Hurray for OpenGL ES! Figure 12-10 shows the texture.