Line colormapping

Nearly all objects in Pygfx can have a colormap. And the texcoords can also be scaled using material.maprange. This is useful in scientific applications, where texcoords can e.g. mean temperature of force.

The same approach can be used in points and meshes (and images and volumes, where this concept is commonly known as contrast limits.)

import numpy as np
from rendercanvas.auto import RenderCanvas, loop
import pygfx as gfx


canvas = RenderCanvas(size=(1000, 1000))
renderer = gfx.WgpuRenderer(canvas)

x = np.linspace(0, 4 * np.pi, 1000)
y = np.sin(x)


positions = np.array([x * 100, y * 100, np.zeros_like(x)], np.float32).T.copy()
mapcoords = y.astype(np.float32) * 8  # so values are in [-8, 8]

geometry = gfx.Geometry(positions=positions, texcoords=mapcoords)

line1 = gfx.Line(
    geometry,
    gfx.LineMaterial(
        thickness=20,
        color_mode="vertex_map",
        map=gfx.cm.viridis,
        maprange=None,  # default (0, 1)
    ),
)

line2 = gfx.Line(
    geometry,
    gfx.LineMaterial(
        thickness=20,
        map=gfx.cm.viridis,
        maprange=(-8, 8),  # full range
    ),
)
line3 = gfx.Line(
    geometry,
    gfx.LineMaterial(
        thickness=20,
        color_mode="vertex_map",
        map=gfx.cm.viridis,
        maprange=(-12, 12),  # zoomed out
    ),
)

line4 = gfx.Line(
    geometry,
    gfx.LineMaterial(
        thickness=20,
        color_mode="vertex_map",
        map=gfx.cm.viridis,
        maprange=(0, 10),  # Only positive half
    ),
)

for line in (line1, line2, line3, line4):
    line.material.thickness_space = "screen"

line1.local.position = 0, 0, 0
line2.local.position = 0, -500, 0
line3.local.position = 0, -1000, 0
line4.local.position = 0, -1500, 0

scene = gfx.Scene()
scene.add(line1, line2, line3, line4)

camera = gfx.OrthographicCamera()
camera.show_object(scene)

controller = gfx.OrbitController(camera, register_events=renderer)

canvas.request_draw(lambda: renderer.render(scene, camera))

if __name__ == "__main__":
    print(__doc__)
    loop.run()

Interactive example

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