Why does my lightning only works when pos. var. declared in display() method?

OpenGL Development JOGL Development
#1

I have a frustrating problem. I want to light up the sphere, like when the sun lights up the moon.

It works with this code:


public void display(GLAutoDrawable drawable) {
     gl.glClearColor (0.0f, 0.0f, 0.0f, 0.0f);
     gl.glShadeModel (GL.GL_SMOOTH);

     float light_position[] = { -5.0f, 7.0f, sunrise, 0.0f };  // Works if this line is inside the display() method
 
     gl.glLightfv(GL.GL_LIGHT0, GL.GL_SPECULAR, FloatBuffer.wrap(light0_ambient));
     gl.glMaterialfv(GL.GL_FRONT, GL.GL_SPECULAR, FloatBuffer.wrap(mat_specular));
     gl.glMaterialfv(GL.GL_FRONT, GL.GL_SHININESS, FloatBuffer.wrap(mat_shininess));
     gl.glLightfv(GL.GL_LIGHT0, GL.GL_POSITION, FloatBuffer.wrap(light_position));
     ...
     sunrise += 0.02f;
     ...

If I place the line:

float light_position[] = { -5.0f, 7.0f, sunrise, 0.0f };

outside the display() method so it becomes a class member, then the animation doesn´t work and the sun seems to be still. How come?

#2

in


float light_position[] = { -5.0f, 7.0f, sunrise, 0.0f };

the value of sunrise is copied to the light_position[] array. So if you change sunrise afterwards it has no effect on the value in the array.