BIMBase之python建模宝典:双坡屋顶

BIMBase自从2021年发布以来获得了众多关心国产BIM和业务数字化转型的圈内老法师的关注，除了是国内首款完全自主知识产权的的BIMBase系统，实现建筑信息模型（BIM）关键核心技术自主研发安全可控。

同时开创了BIM X PYthon的技术跨界混搭风，得以让建模可以通过快速编程实现。

So！

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【BIMBase之python建模宝典】

今日分享第十弹

生活中的屋顶大多为双坡，部分由于采光要求会有主次屋顶之分。如何根据对称性和三维斜面拉伸高效运用Python参数化建模创建双坡屋顶？今天，来带你揭晓答案！

图 1 双坡屋顶

建模方法

BIMBase双坡屋顶

① 引用pyp3d，定义参数，变量赋值（既然有主次屋顶之分必然须定义两部分各自参数！）

class 双坡屋顶(Component):

def __init__(self):

Component.__init__(self)

self['双坡屋顶'] = Attr(None, show = True)

self['屋顶坡度'] = Attr(30.0, obvious = True)

self['屋顶厚度'] = Attr(295.0, obvious = True)

self['屋顶高差'] = Attr(231.0, obvious = True, readonly = True)

# 主屋顶

self['主屋顶宽度'] = Attr(2000.0, obvious = True, group = '主屋顶')

self['主屋顶长度'] = Attr(9000.0, obvious = True, group = '主屋顶')

# 次屋顶

self['次屋顶宽度'] = Attr(1600.0, obvious = True, group = '次屋顶')

self['次屋顶长度'] = Attr(1600.0, obvious = True, readonly = True, group = '次屋顶')

self['次屋顶方位'] = Attr('右', combo = ['右', '左'], obvious = True, group = '次屋顶')

self['次屋顶间距'] = Attr(4000.0, obvious = True, group = '次屋顶')

self.replace()

@export

def replace(self):

# 主屋顶

mainRoofWidth = self['主屋顶宽度']

mainRoofLength = self['主屋顶长度']

# 次屋顶

viceRoofWidth = self['次屋顶宽度']

self['次屋顶长度'] = viceRoofWidth

viceRoofLength = self['次屋顶长度']

viceRoofSpace = self['次屋顶间距']

# 公有属性

roofSlope = self['屋顶坡度']

roofThickness = self['屋顶厚度']

self['屋顶高差'] = (mainRoofWidth-viceRoofWidth)*tan(roofSlope/180*pi)

roofLevDiff = self['屋顶高差']

② 主屋顶

运用Extrusion函数直接对三维斜面leftRoof_sec进行厚度方向的拉伸，构造左侧主屋顶，根据对称性原理运用mirror函数构造对称部分（一定注意对称轴的方位呀！）最后只需小小组合便成功得到主屋顶啦。

leftRoof_sec = [Vec3(0, -roofLength/2, 0),

Vec3(roofWidth, -roofLength/2,

roofWidth*tan(slope/180*pi)),

Vec3(roofWidth, roofLength/2,

roofWidth*tan(slope/180*pi)),

Vec3(0, roofLength/2, 0)]

leftRoof = trans(-roofWidth, 0, -roofWidth*tan(slope/180*pi))*\

Extrusion(leftRoof_sec, Vec3

(0, 0, -roofThickness/cos(slope/180*pi)))

rightRoof = mirror_yoz()*leftRoof

doublePitchRoof = unite(leftRoof, rightRoof)

③ 次屋顶

为提高代码复用能力，本文将生成次屋顶的过程存放于一个自定义函数中。

def doublePitchRoof (roofWidth, roofLength, roofThickness, slope, isMain = True):

相比主屋顶，次屋顶的构造有一定的难度，需要细致分析。首先运用上述主屋顶的方式代入次屋顶的相关变量，得到一个形状与主屋顶类似的构件，运用布尔减得到双坡屋顶中次屋顶部分。

if not isMain:

lengthSlope = trans(0, roofLength/2, 0)*\

Sweep(rotx(slope/180*pi)*\

Section(scale(4*sin(slope/180*pi)/

cos(slope/180*pi)*roofWidth)*Arc()),

Line(Vec3(0, 0, 0), Vec3(0, 2*roofLength, 0)))

doublePitchRoof = doublePitchRoof-lengthSlope

hollow = Extrusion([Vec3(-roofWidth, -roofLength/2, -roofWidth*tan(slope/180*pi)/

-roofThickness/cos(slope/180*pi)),

Vec3(0, -roofLength/2,

-roofThickness/cos(slope/180*pi)),

Vec3(roofWidth, -roofLength/2,

-roofWidth*tan(slope/180*pi)/

-roofThickness/cos(slope/180*pi))],

Vec3(0, roofLength, 0))

return doublePitchRoof, hollow # 返回包含次屋顶和次屋顶应减切区域的列表

return doublePitchRoof

④ 镜像组合

你以为到这就结束了？

千万别忘记次屋顶的方位问题，运用translate、rotate函数进行变位，再次使用mirror函数对称得到2号次屋顶，到此，次屋顶构造完成。通过doublePitchRoof函数返回的包含次屋顶屋面和次屋顶应该剪切区域的列表，得到布尔减后的主屋顶。

# 主屋顶

mainRoof = doublePitchRoof(mainRoofWidth, mainRoofLength, roofThickness, roofSlope)

# 次屋顶

viceRoof1 = trans(mainRoofWidth-viceRoofLength/2, viceRoofSpace/2, -roofLevDiff)*\

rotz(pi/2)*\

doublePitchRoof(viceRoofWidth, viceRoofLength, roofThickness, roofSlope, False)

if self['次屋顶方位'] == '左':

viceRoof1 = mirror_yoz()*viceRoof1

viceRoof2 = mirror_xoz()*viceRoof1

viceRoof = Combine(viceRoof1[0], viceRoof2[0])

mainRoof = mainRoof-viceRoof1[1]-viceRoof2[1]

self['双坡屋顶'] = Combine(mainRoof, viceRoof)

方法总结

BIMBase双坡屋顶

1. Extrusion可以对三维面进行拉伸；

2. 镜像函数mirror仅需一步即可实现构件的对称布置。

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