pyopengl绘制一个半透明的圆柱

可以使用OpenGL的混合功能来绘制半透明的圆柱。具体步骤如下：

1. 开启混合功能，启用透明度：

glEnable(GL_BLEND)
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)

2. 绘制圆柱的侧面和顶面：

glBegin(GL_TRIANGLE_STRIP)
for i in range(n+1):
    x = radius * cos(i * 2 * pi / n)
    y = radius * sin(i * 2 * pi / n)
    glColor4f(1.0, 1.0, 1.0, alpha)
    glVertex3f(x, y, -h/2)
    glVertex3f(x, y, h/2)
glEnd()

glBegin(GL_TRIANGLE_FAN)
glColor4f(1.0, 1.0, 1.0, alpha)
glVertex3f(0, 0, h/2)
for i in range(n+1):
    x = radius * cos(i * 2 * pi / n)
    y = radius * sin(i * 2 * pi / n)
    glVertex3f(x, y, h/2)
glEnd()

glBegin(GL_TRIANGLE_FAN)
glColor4f(1.0, 1.0, 1.0, alpha)
glVertex3f(0, 0, -h/2)
for i in range(n+1):
    x = radius * cos(i * 2 * pi / n)
    y = radius * sin(i * 2 * pi / n)
    glVertex3f(x, y, -h/2)
glEnd()

其中，n为圆柱的面数，radius为圆柱的半径，h为圆柱的高度，alpha为透明度。

3. 关闭混合功能：

glDisable(GL_BLEND)

完整的代码示例如下：

from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GLUT import *
from math import pi, sin, cos

def draw_cylinder(radius, h, alpha, n=30):
    glEnable(GL_BLEND)
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
    
    glBegin(GL_TRIANGLE_STRIP)
    for i in range(n+1):
        x = radius * cos(i * 2 * pi / n)
        y = radius * sin(i * 2 * pi / n)
        glColor4f(1.0, 1.0, 1.0, alpha)
        glVertex3f(x, y, -h/2)
        glVertex3f(x, y, h/2)
    glEnd()

    glBegin(GL_TRIANGLE_FAN)
    glColor4f(1.0, 1.0, 1.0, alpha)
    glVertex3f(0, 0, h/2)
    for i in range(n+1):
        x = radius * cos(i * 2 * pi / n)
        y = radius * sin(i * 2 * pi / n)
        glVertex3f(x, y, h/2)
    glEnd()

    glBegin(GL_TRIANGLE_FAN)
    glColor4f(1.0, 1.0, 1.0, alpha)
    glVertex3f(0, 0, -h/2)
    for i in range(n+1):
        x = radius * cos(i * 2 * pi / n)
        y = radius * sin(i * 2 * pi / n)
        glVertex3f(x, y, -h/2)
    glEnd()
    
    glDisable(GL_BLEND)

def display():
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    glMatrixMode(GL_MODELVIEW)
    glLoadIdentity()
    gluLookAt(0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0)
    draw_cylinder(1.0, 2.0, 0.5)
    glutSwapBuffers()

glutInit()
glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH)
glutInitWindowSize(400, 400)
glutCreateWindow(b"PyOpenGL")
glutDisplayFunc(display)
glutMainLoop()