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"""This example is a port to ModernGL of code by Nicolas P. Rougier from his "Python & OpenGL
for Scientific Visualization" free online book. Available under the (new) BSD License.
Book is available here:
https://github.com/rougier/python-opengl
Background information on this code:
https://github.com/rougier/python-opengl/blob/master/09-lines.rst
Original code on which this example is based:
https://github.com/rougier/python-opengl/blob/master/code/chapter-09/geom-path.py
"""
import numpy as np
from pyrr import Matrix44
import moderngl
from _example import Example
# prepare geometry
def star(inner=0.45, outer=1.0, n=5):
R = np.array([inner, outer] * n)
T = np.linspace(-0.5 * np.pi, 1.5 * np.pi, 2 * n, endpoint=False)
P = np.zeros((2 * n, 2))
P[:, 0] = R * np.cos(T)
P[:, 1] = R * np.sin(T)
return np.vstack([P, P[0]])
def rect(x, y, w, h):
return np.array([(x, y), (x + w, y), (x + w, y + h), (x, y + h), (x, y)])
def build_buffers(lines):
"""Prepare the buffers for multi-polyline rendering. Closed polyline must have their
last point identical to their first point."""
lines = [np.array(line, dtype="f4") for line in lines]
indices = []
reset_index = [-1]
start_index = 0
for line in lines:
if np.all(line[0] == line[-1]): # closed path
idx = np.arange(len(line) + 3) - 1
idx[0], idx[-2], idx[-1] = len(line) - 1, 0, 1
else:
idx = np.arange(len(line) + 2) - 1
idx[0], idx[-1] = 0, len(line) - 1
indices.append(idx + start_index)
start_index += len(line)
indices.append(reset_index)
return np.vstack(lines).astype("f4"), np.concatenate(indices).astype("i4")
class RichLines(Example):
title = "Rich Lines"
gl_version = (3, 3)
def __init__(self, **kwargs):
super().__init__(**kwargs)
self.line_prog = self.load_program("rich_lines.glsl")
lines = [
star(n=5) * 300 + (400, 400),
star(n=8) * 150 + (900, 200),
rect(900, 600, 150, 50),
[(1200, 100), (1400, 200), (1300, 100)],
]
vertex, index = build_buffers(lines)
vbo = self.ctx.buffer(vertex)
ibo = self.ctx.buffer(index)
self.vao = self.ctx.simple_vertex_array(self.line_prog, vbo, "position",
index_buffer=ibo)
# Set the desired properties for the lines.
# Note:
# - round cap/ends are used if miter_limit < 0
# - antialias value is in model space and should probably be scaled to be ~1.5px in
# screen space
self.line_prog["linewidth"].value = 15
self.line_prog["antialias"].value = 1.5
self.line_prog["miter_limit"].value = -1
self.line_prog["color"].value = 0, 0, 1, 1
self.line_prog["projection"].write(
Matrix44.orthogonal_projection(0, 1600, 800, 0, 0.5, -0.5, dtype="f4")
)
def render(self, time, frame_time):
self.ctx.clear(1, 1, 1, 1)
self.ctx.enable(moderngl.BLEND)
self.vao.render(moderngl.LINE_STRIP_ADJACENCY)
if __name__ == '__main__':
RichLines.run()
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