I have tried to create a menu to change the color of a local light in my simulation. The simulation is a central sphere being a planet, around an atmosphere with transparency smaller than 1 and a local light source. Here is my code so far:
""" Import libraries """
import vpython as vp
import numpy as np
import sys
""" Create Canvas """
canvas = vp.canvas(width=1080, height=720)
scene = vp.scene
""" Create objects """
# Define the planet
planet_radius = 5
planet_texture = 'planet.jpg' # You can replace this with your own custom picture
planet = vp.sphere(radius=planet_radius, texture=vp.textures.earth, shininess=0)
# Define the atmosphere
atm_thickness = 3.0 # You can modify this using a slide cursor
atm_density = 0.5 # You can modify this using a slide cursor
atm_radius = planet.radius+atm_thickness
atm = vp.sphere(radius=atm_radius, opacity=0.25)
# Define the light source
light_type = 'sun' # You can modify this using a drop-down menu
light_wavelength = 550 # You can modify this using a slide cursor
light_size = 2 # You can modify this using a slide cursor
light_intensity = 1.0 # You can modify this using a slide cursor
pos_drift = 50
light_pos = vp.vector(atm_radius+pos_drift, atm_radius+pos_drift, atm_radius+pos_drift)
light = vp.local_light(pos=light_pos, color=vp.color.red, radius=light_size)
# Define the camera
scene.autoscale = False
scene.range = 10
scene.forward = vp.vector(0, 0, -1)
scene.up = vp.vector(0, 1, 0)
scene.caption = 'Click and drag on the light source to move it. Use the drop-down menu and slide cursors to adjust its properties.'
""" Define the event handlers """
def on_light_down(evt):
global light_dragging, light_drag_pos
light_dragging = True
light_drag_pos = evt.pos
def on_light_move(evt):
global light_dragging, light_drag_pos
if light_dragging:
light.pos += evt.pos - light_drag_pos
light_drag_pos = evt.pos
def on_light_up(evt):
global light_dragging
light_dragging = False
# Bind the event handlers
vp.scene.bind('mousedown', on_light_down)
vp.scene.bind('mousemove', on_light_move)
vp.scene.bind('mouseup', on_light_up)
def on_mouse_down(event):
global dragging, last_mouse_pos
obj = scene.mouse.pick
if obj == light:
dragging = True
last_mouse_pos = scene.mouse.pos
canvas.bind('mousedown', on_mouse_down)
# Create a slider that controls the x position of the sphere
def set_x_position(slider):
light.pos.x = slider.value
slider = vp.slider(min=-25, max=25, length=250, bind=set_x_position)
# Create a menu to change the light colour
def M(m):
global light
val = m.selected
if val == "sun":
light.color = vp.color.white
elif val == "red":
light.color = vp.color.red
elif val == "yellow":
light.color = vp.color.yellow
elif val == "blue":
light.color = vp.color.blue
menu = vp.menu(choices=['sun', 'red', 'yellow', 'blue'], index=0, bind=M)
# Define the exit function
def exit_simulation():
canvas.delete()
# sys.exit()
# Create the exit button
exit_button = vp.button(bind=exit_simulation, text="Exit Simulation")
""" Run the simulation """
while True:
vp.rate(30)
# Update the atmosphere
atm.radius = planet.radius+atm_thickness
atm.opacity = 0.25*atm_density
# Update the light source
light.radius = light_size
light.intensity = light_intensity
if light_type == 'sun':
light.color = vp.color.white
elif light_type == 'red_dwarf':
light.color = vp.color.red
elif light_type == 'white_dwarf':
light.color = vp.color.white
# Update the camera
vp.scene.center = planet.pos
# Update the planet texture
planet.texture = planet_texture
However, the light either doesn't change color of blip for a split second and go back to the initial color. It probably has to do with how the new color of the light source is assigned in the M function of the menu. Is there a way to fix that?
I believe its because of the values of light_type in the while. Try removing the three conditions and add in the update functions light_type = val at the end to ensure the light source type changes. This should fix your problem.