Android Invaders: The Grand Finale - Beginning Android Games - page 623

and texture outside the for loop, we have to unbind and rebind them before we can render an
explosion instead of an invader.
private void renderShields(GL10 gl, List<Shield> shields) {
gl.glEnable(GL10. GL_BLEND );
gl.glBlendFunc(GL10. GL_SRC_ALPHA , GL10. GL_ONE_MINUS_SRC_ALPHA );
gl.glColor4f(0, 0, 1, 0.4f);
Assets. shieldModel .bind();
int len = shields.size();
for ( int i = 0; i < len; i++) {
Shield shield = shields.get(i);
gl.glPushMatrix();
gl.glTranslatef(shield.position.x, shield.position.y,
shield.position.z);
Assets. shieldModel .draw(GL10. GL_TRIANGLES , 0,
Assets. shieldModel .getNumVertices());
gl.glPopMatrix();
}
Assets. shieldModel .unbind();
gl.glColor4f(1, 1, 1, 1f);
gl.glDisable(GL10. GL_BLEND );
}
The renderShields() method renders the shield blocks. We apply the same principle as in the
case of rendering invaders. We only bind the model once. Since we have no texture, we don't
need to bind one. However, we need to enable blending. We set the global vertex color to blue,
with the alpha component set to 0.4. This will make the shield blocks a little transparent.
private void renderShots(GL10 gl, List<Shot> shots) {
gl.glColor4f(1, 1, 0, 1);
Assets. shotModel .bind();
int len = shots.size();
for ( int i = 0; i < len; i++) {
Shot shot = shots.get(i);
gl.glPushMatrix();
gl.glTranslatef(shot.position.x, shot.position.y, shot.position.z);
Assets. shotModel .draw(GL10. GL_TRIANGLES , 0,
Assets. shotModel .getNumVertices());
gl.glPopMatrix();
}
Assets. shotModel .unbind();
gl.glColor4f(1, 1, 1, 1);
}
Rendering the shots in renderShots() is the same as rendering the shields, except that we don't
use blending and we use a different vertex color (yellow).
private void renderExplosion(GL10 gl, Vector3 position, float stateTime) {
TextureRegion frame = Assets. explosionAnim .getKeyFrame(stateTime,
Animation. ANIMATION_NONLOOPING );