Well, not exactly an answer to your question, but perhaps this is useful for you.
I prefer sky spheres or sky domes over sky boxes, since it easier to move clouds around on a sphere than on a box. The following script creates a textured sky dome (the upper part of a hemisphere, from zenith down to about 45 degrees). It can be used with a tileable sky/cloud texture.
I don’t create a full hemisphere because I don’t like the vertical parts at the horizon, and even with scaling in horizontal dimension you have these vertical parts. A hemisphere would be ok for starfields since the stars a very very far away, while clouds usually have a finite altitude. 45 degrees would be a cloud altitude of about 6000km if I am right.
This approach works well with tileable, moving cloud textures, but if you want to have parts of the horizon (distant mountains etc.) on you sky then it won’t help you.
Usage: just load the model, re-parent it somewhere, and scale it to your camera’s far distance (actually, a bit less). Oh, and move it around with your camera.
enn0x
from pandac.PandaModules import EggData
from pandac.PandaModules import EggPolygon
from pandac.PandaModules import EggTexture
from pandac.PandaModules import EggVertex
from pandac.PandaModules import EggVertexPool
from pandac.PandaModules import Filename
from pandac.PandaModules import Point2D
from pandac.PandaModules import Point3D
import math
import os
nrows = 6
ncols = 16
uvscale = 2.8
texture = 'clouds.png'
sqrt2 = math.sqrt( 2.0 )
def makePoly( g, vlist ):
_poly = EggPolygon( )
for _v in vlist:
_poly.addVertex( _v )
g.addChild( _poly )
def makeVertex( x, y, z, u, v ):
_v = EggVertex( )
_v.setPos( Point3D( x, y, z ) )
_v.setUv( Point2D( u, v ) )
vp.addVertex( _v )
return _v
# egg data
vp = EggVertexPool( 'sky' )
data = EggData( )
data.addChild( vp )
data.setCoordinateSystem( 1 ) # CS_zup_right
# vertices
zenith = makeVertex( 0.0, 0.0, sqrt2 - 1.0, 0.0, 0.0 )
vertices = { }
for j in range( 1, nrows + 1 ):
for i in range( ncols ):
phi = math.radians( 360.0 / ncols * i )
theta = math.radians( 45.0 / nrows * j )
x = sqrt2 * math.sin( theta ) * math.cos( phi )
y = sqrt2 * math.sin( theta ) * math.sin( phi )
z = sqrt2 * math.cos( theta ) - 1.0
factor = uvscale
u = x * factor
v = y * factor
vertices[ ( j, i ) ] = makeVertex( x, y, z, u, v )
# triangles ( first row )
for i in range( ncols ):
v1 = zenith
v2 = vertices[ ( 1, ( i + 1 ) % ncols ) ]
v3 = vertices[ ( 1, i ) ]
makePoly( data, [ v1, v2, v3 ] )
# quads ( other rows )
for j in range( 1, nrows ):
for i in range( ncols ):
i0 = i
i1 = ( i + 1 ) % ncols
j0 = j
j1 = j + 1
v1 = vertices[ ( j0, i0 ) ]
v2 = vertices[ ( j0, i1 ) ]
v3 = vertices[ ( j1, i1 ) ]
v4 = vertices[ ( j1, i0 ) ]
makePoly( data, [ v1, v2, v3, v4 ] )
# texture
tex = EggTexture( 'clouds', texture )
tex.setMagfilter( EggTexture.FTLinearMipmapLinear )
tex.setMinfilter( EggTexture.FTLinearMipmapLinear )
n = data.getFirstChild( )
while n:
if type( n ) == EggPolygon:
n.addTexture( tex )
n = data.getNextChild( )
# save
data.writeEgg( Filename( 'sky.egg' ) )
# egg2bam
os.system( 'egg2bam sky.egg -o sky.bam' )