vpython label pixel_pos problem

pixel_pos_problem.py

import vpython as vp
import random
#import math

# description: a world with vertical cylinders (axis = vp.vec(0,0,1), base of all cylinders is at world position z=0
#              the base of the cylinder has a location label (white text)
#              the top of each cylinder has a value label (green text)

# problem: finding out pixel_pos of location labels (at the base of a cylinder) and the value labels( at the top of a cylinder)
#          the pixel pos is not the world coordinates, but the coordinate in pixels
#          (from the screen center or from the lower left corner)
#          where an object (a label) appears on the screen.

class Sim:
    demand = {}
    width = 1200
    height = 800
    min_x = -10
    max_x = 10
    min_y = -10
    max_y = 10
    min_z = 0.1
    max_z = 1.5
    radius = 0.1

    show_location_labels = True
    show_value_labels = True
    merge_labels = False

    grid_color = vp.vec(0.7,0.7,0.7)
    #factor = 0.87

class Column(vp.cylinder):
    container = []
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        if "abbr" in kwargs:
            self.abbr = kwargs["abbr"]
        else:
            raise ValueError("abbr missing in arguments")
        Column.container.append(self)
        self.original_pos = vp.vec(self.pos.x, self.pos.y, self.pos.z)


class ValueLabel(vp.label):
    container = []
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        if "abbr" in kwargs:
            self.abbr = kwargs["abbr"]
        else:
            raise ValueError("abbr missing in arguments")
        ValueLabel.container.append(self)
        self.original_pos = vp.vec(self.pos.x, self.pos.y, self.pos.z)


class LocationLabel(vp.label):
    container = []
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        if "abbr" in kwargs:
            self.abbr = kwargs["abbr"]
        else:
            raise ValueError("abbr missing in arguments")
        LocationLabel.container.append(self)
        self.original_pos = vp.vec(self.pos.x, self.pos.y, self.pos.z)

class GridLine(vp.curve):
    container = []
    def __init__(self,**kwargs):
        super().__init__(**kwargs)
        GridLine.container.append(self)

def widget_func_show_location_labels(b):
    Sim.show_location_labels = b.checked
    for l in LocationLabel.container:
        l.visible = b.checked

def widget_func_show_value_labels(b):
    Sim.show_value_labels = b.checked
    for l in ValueLabel.container:
        l.visible = b.checked



def widget_func_grid0(b):
    # white lines at height 0
    for line in GridLine.container:
        if line.color == Sim.grid_color:
            line.visible = b.checked

def widget_func_grid1(b):
    # yellow lines at height 1
    for line in GridLine.container:
        if line.color == vp.color.yellow:
            line.visible = b.checked


def widget_func_box(b):
    for l in LocationLabel.container:
        l.box = b.checked

def show_pixelpositions():
    Sim.bigtext.text = ""
    #for c in Column.container:
    #    base_pos = c.pos
    #    top_pos = c.pos + c.axis
    #    Sim.bigtext.text += f"{c.abbr}: base: {world_to_pixel(base_pos)} top: {world_to_pixel(top_pos)} _offset {c._offset}\n"
    #Sim.bigtext.text +=f"vertexcount: {scene.vertexCount}\n"
    Sim.bigtext.text +=f"pixel_to_world: {scene.pixel_to_world}\n"
    Sim.bigtext.text +=f"world_to_pixel: {1/scene.pixel_to_world}\n"
    Sim.bigtext.text +=f"scene.center: {scene.center}\n"
    Sim.bigtext.text +=f"scene.range: {scene.range}\n"
    Sim.bigtext.text +=f"scene.camera.pos: {scene.camera.pos}\n"
    Sim.bigtext.text +=f"scene.fov: {scene.fov}\n"
    Sim.bigtext.text +=f"d: {vp.mag(scene.center-scene.camera.pos)}"


# ---------------------------------------- main --------------------------------

scene = vp.canvas(width=Sim.width, height=Sim.height, background=vp.color.purple, align="left")


# make 3 arrows in the world center for orientation
vp.arrow(axis=vp.vec(1,0,0), color=vp.color.red)
vp.arrow(axis=vp.vec(0,1,0), color=vp.color.green)
vp.arrow(axis=vp.vec(0,0,1), color=vp.color.blue)

# 3d grid and bluebox
bluebox = vp.box(pos=vp.vec(0,0,-0.1), size=vp.vec(Sim.max_x*2, Sim.max_y*2, 0.049), color=vp.vec(0,0,0.5))
# white grid at height 0
for x in range(Sim.min_x, Sim.max_x+1):
    GridLine(pos=[vp.vec(x,Sim.min_y,0), vp.vec(x, Sim.max_y, 0)], color=Sim.grid_color)
for y in range(Sim.min_y, Sim.max_y+1):
    GridLine(pos=[vp.vec(Sim.min_x, y, 0), vp.vec(Sim.max_x, y, 0)], color=Sim.grid_color)
# yellow grid at height 1
for x in range(Sim.min_x, Sim.max_x+1):
    GridLine(pos=[vp.vec(x,Sim.min_y,1), vp.vec(x, Sim.max_y, 1)], color=vp.color.yellow, visible=False)
for y in range(Sim.min_y, Sim.max_y+1):
    GridLine(pos=[vp.vec(Sim.min_x, y, 1), vp.vec(Sim.max_x, y, 1)], color=vp.color.yellow, visible=False)

# generate nodes (yellow vertical cylinders that have a location label at the base and a value label at the top)

for n in range(1,6):
    #x = random.uniform(Sim.min_x, Sim.max_x)
    x = random.gauss(mu=0, sigma = 3)
    #y = random.uniform(Sim.min_x, Sim.max_x)
    y = random.gauss(mu=0, sigma = 3)
    z = random.uniform(Sim.min_z, Sim.max_z)
    abbr_text = f"node_{n:03}"
    Sim.demand[abbr_text] = z
    Column(pos=vp.vec(x,y,0), axis=vp.vec(0,0,z), color=vp.color.yellow, radius=Sim.radius, abbr=abbr_text,opacity=0.5)
    LocationLabel(pos=vp.vec(x,y,0), abbr=abbr_text, text=abbr_text, align="left", yoffset=20, xoffset=20, box=False, opacity=0)
    ValueLabel(pos=vp.vec(x,y,z), abbr=abbr_text, text=f"{z:.2f}", align="center",box=False, opacity=0,
               color=vp.color.green, visible=True,xoffset= -20, yoffset=-20)


# green labels with pixel_pos (xy position on the screen)
for x in range(0,Sim.width+1,100):
    vp.label(pixel_pos=True, pos=vp.vec(x, 10, 0), text=f"|{x}", color=vp.color.green, box=False, align="left")
for y in range(0, Sim.height+1,100):
    vp.label(pixel_pos=True, pos=vp.vec(0, y, 0), text=f"-{y}", color=vp.color.green, box=False, align="left")
# green screen center label
vp.label(pixel_pos = True, pos=vp.vec(Sim.width/2,Sim.height/2,0), text="+", align="center", box=False, color=vp.color.green, opacity=0)


# ------------------  UI ------------------
scene.append_to_caption("\n toggle: ")
vp.checkbox(text="grid0", bind=widget_func_grid0, checked=True)
vp.checkbox(text="grid1", bind=widget_func_grid1, checked=False)
#vp.button(text="pixel", bind=widget_func_pixel)
vp.checkbox(text="location box", bind=widget_func_box, checked=False)
vp.checkbox(text="location labels", bind=widget_func_show_location_labels, checked=Sim.show_location_labels)
vp.checkbox(text="value labels", bind=widget_func_show_value_labels, checked=Sim.show_value_labels)
scene.append_to_caption("\n")
scene.append_to_caption("\n")
Sim.bigtext = vp.wtext(text="base, top", pos=scene.caption_anchor)

# camera restrictions
scene.userspin = False

while True:
    vp.rate(60)
    show_pixelpositions()