3D Programming Tricks - Beginning Android Games - page 538

public class DirectionalLight {
float [] ambient = { 0.2f, 0.2f, 0.2f, 1.0f };
float [] diffuse = { 1.0f, 1.0f, 1.0f, 1.0f };
float [] specular = { 0.0f, 0.0f, 0.0f, 1.0f };
float [] direction = { 0, 0, -1, 0 };
int lastLightId = 0;
public void setAmbient( float r, float g, float b, float a) {
ambient[0] = r;
ambient[1] = g;
ambient[2] = b;
ambient[3] = a;
}
public void setDiffuse( float r, float g, float b, float a) {
diffuse[0] = r;
diffuse[1] = g;
diffuse[2] = b;
diffuse[3] = a;
}
public void setSpecular( float r, float g, float b, float a) {
specular[0] = r;
specular[1] = g;
specular[2] = b;
specular[3] = a;
}
public void setDirection( float x, float y, float z) {
direction[0] = -x;
direction[1] = -y;
direction[2] = -z;
}
public void enable(GL10 gl, int lightId) {
gl.glEnable(lightId);
gl.glLightfv(lightId, GL10. GL_AMBIENT , ambient, 0);
gl.glLightfv(lightId, GL10. GL_DIFFUSE , diffuse, 0);
gl.glLightfv(lightId, GL10. GL_SPECULAR , specular, 0);
gl.glLightfv(lightId, GL10. GL_POSITION , direction, 0);
lastLightId = lightId;
}
public void disable(GL10 gl) {
gl.glDisable(lastLightId);
}
}
Our helper class is nearly identical to the PointLight class. The only difference is that the
direction array has its fourth element set to 1. We also have a setDirection() method instead of a
setPosition() method. The setDirection() method allows us to specify a direction, like (-1,0,0)
so that the light comes from the right side. Inside the method, we just negate all of the vector