If I create a Volume with some Faces and then
mirror it by giving it a negative scale factor
along one axis, the front and back faces get
reversed. That's a bit annoying, but it can
be worked around by making the faces double
sided.
However, if I create a Shape out of it and
create a mirrored instance of the shape, it
doesn't appear *at all*, even with double
sided faces.
Attached is a program that demonstrates the
problem. It should display two pyramids, one
of them upside down, but the second one is
invisible. Changing the line
pyramid2.scale(1, -1, 1)
to
pyramid2.scale(-1, -1, 1)
i.e. a non-mirroring transformation, causes it
to reappear.
Anyone know what's going on?
--
Greg
# -*- indent-tabs-mode: t -*-
# Soya 3D tutorial
# Copyright (C) 2001-2004 Jean-Baptiste LAMY
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
# modeling-1: Faces : the pyramid
# requires the basic-* lessons.
# Models are usually designed in Blender and imported in Soya (as in lesson
basic-1.py),
# but you can also create them from scratch, using Soya primitives. Learning
this is
# the purpose of the modeling-* tutorial series.
# In this lesson, we'll build a pyramid, made of a quad base and 4 triangles.
# Imports and inits Soya (see lesson basic-1.py).
import sys, os, os.path, soya
soya.init()
soya.path.append(os.path.join(os.path.dirname(sys.argv[0]), "data"))
# Creates the scene.
scene = soya.World()
# Creates the World that will contain the pyramid. As previously stated, the
# pyramid is composed of 5 faces; this world is used to group those 5 faces
# (exactly like a Frame can be used in Tkinter to group different widgets).
# The pyramid's parent is the scene.
pyramid = soya.World()
# Creates the first face, the quad base of the pyramid.
# The first argument of the Face constructor is the parent World (the pyramid),
# the second is the list of vertices and the third is the material.
# The number of vertices determines the Face's nature:
# - 1: a plot
# - 2: a line
# - 3: a triangle
# - 4: a quad
# - +: a polygon
# The vertices is a list of Vertex object. A Vertex is a subclass of Point that
can have
# some modeling attributes like colors or texture coordinates (we'll see them
is further
# lessons) The first argument of the constructor is (again) the parent, and the
three
# following one are the x, y and z coordinates.
# As 3D object, Point, Vector or Vertex have a parent too, though they are not
# considered as "children". The parent is used for automatic coordinates
# conversion, which will be detailed in a further lesson. Here, the coordinates
# are defined in the pyramid coordinate system.
# The order of the vertices in the list determines which side of the face is
# visible (for triangles, quads and polygons); you can get both side visible
# by setting the "double_sided" attribute to 1.
soya.Face(pyramid, [soya.Vertex(pyramid, 0.5, -0.5, 0.5),
soya.Vertex(pyramid, -0.5, -0.5, 0.5),
soya.Vertex(pyramid, -0.5, -0.5, -0.5),
soya.Vertex(pyramid, 0.5, -0.5, -0.5),
]).double_sided = True
# Similarly, creates the 4 triangles.
# Here, we create different vertices ; you can also use the same vertex when 2
vertices
# have the same coordinates and attributes. Both yields the same final result
(including
# in performance).
soya.Face(pyramid, [soya.Vertex(pyramid, -0.5, -0.5, 0.5),
soya.Vertex(pyramid, 0.5, -0.5, 0.5),
soya.Vertex(pyramid, 0.0, 0.5, 0.0),
]).double_sided = True
soya.Face(pyramid, [soya.Vertex(pyramid, 0.5, -0.5, -0.5),
soya.Vertex(pyramid, -0.5, -0.5, -0.5),
soya.Vertex(pyramid, 0.0, 0.5, 0.0),
]).double_sided = True
soya.Face(pyramid, [soya.Vertex(pyramid, 0.5, -0.5, 0.5),
soya.Vertex(pyramid, 0.5, -0.5, -0.5),
soya.Vertex(pyramid, 0.0, 0.5, 0.0),
]).double_sided = True
soya.Face(pyramid, [soya.Vertex(pyramid, -0.5, -0.5, -0.5),
soya.Vertex(pyramid, -0.5, -0.5, 0.5),
soya.Vertex(pyramid, 0.0, 0.5, 0.0),
]).double_sided = True
pyramid_model = pyramid.shapify()
# Creates a Volume in the scene, that displays the pyramid.
pyramid1 = soya.Volume(scene, pyramid_model)
# Moves and rotates the pyramid (for a better view)
pyramid1.x = -0.7
pyramid1.rotate_y(60.0)
# Creates a second pyramid. Contrary to World, Shape model can be displayed
several
# time at different position.
# Soya separates the model part (the Shape) from the position part (the Volume).
pyramid2 = soya.Volume(scene, pyramid_model)
pyramid2.x = 0.8
pyramid2.rotate_y(45.0)
pyramid2.scale(1, -1, 1)
# Creates a light.
light = soya.Light(scene)
light.set_xyz(1.0, 0.7, 1.0)
# Creates a camera.
camera = soya.Camera(scene)
camera.set_xyz(0.0, 0.0, 2.0)
soya.set_root_widget(camera)
soya.Idler(scene).idle()
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