Visualizing vertex positions and normals
| Author: | Matthias Baas (mbaas@users.sourceforge.net) |
|---|---|
| Date: | 2004/12/20 |
This code example shows the following things:
- How to iterate over all objects in the scene
- How to iterate over mesh vertices and faces
- How to access primitive variables such as normals
- How to process the two storage types "varying" vs "user"/"uniform int XYZfaces[3]"
- How to draw 3D marker and lines
The following script loads a scene and shows the vertices and normals of every mesh in the scene. The vertices are displayed as blue markers and the normals as lines.
Here is the script and a demo file (bunny.3ds) containing the Stanford Bunny.
######################################################################
# Visualizing the vertices and normals of a triangle mesh
#
# This script loads a scene and shows the vertices and normals of
# every mesh in the scene.
#
# Invoke the script via the viewer tool:
# $ viewer.py shownormals.py
######################################################################
def showVertices(mesh):
"""Draw markers at the vertex positions of a triangle mesh.
"""
# Vertices are stored in the local coordinate system of the geometry.
# But as we need the coordinates relative to the world coordinate
# system we have to obtain the transformation L that transforms from
# local to world coordinates.
L = mesh.worldtransform
# Iterate over the vertices and draw a marker at the global vertex
# position L*v.
for v in mesh.verts:
drawMarker(L*v, size=0.07, color=(0,0,1))
def showNormals(mesh):
"""Draw the normals as lines.
A normal is drawn at every vertex position. The normals may either be
specified as "varying normal N" or as "user normal N"/"uniform int Nfaces[3]".
The actual drawing code is in showVaryingNormals() and showUserNormals().
"""
# Check if there are normals available in this mesh
desc = mesh.findVariable("N")
if desc==None:
print 'Mesh "%s" has no normals set.'%mesh.name
return
# Unpack the variable descriptor
name, storage_class, type, mult = desc
# Are the normals stored as "varying normal N"?
if storage_class==VARYING and type==NORMAL and mult==1:
showVaryingNormals(mesh)
# Or are they stored as "user normal N"?
elif storage_class==USER and type==NORMAL and mult==1:
# Check if the normal faces are available
desc = mesh.findVariable("Nfaces")
if desc==None:
print 'Mesh "%s" has no normal faces set.'%mesh.name
else:
name, storage_class, type, mult = desc
if storage_class==UNIFORM and type==INT and mult==3:
# "N" and "Nfaces" is available and of the right type...
showUserNormals(mesh)
else:
print 'Mesh "%s": Invalid declaration of "Nfaces"'%mesh.name
else:
print 'Mesh "%s": Invalid declaration of variable "N".'%mesh.name
def showVaryingNormals(mesh):
"""Draw normals given as "varying normal N".
"""
# Get the world transform to transform the local vertices and normals
# into the world coordinate system
L = mesh.worldtransform
L0 = L*vec3(0)
# Obtain the slot carrying the normals
N = mesh.geom.slot("N")
# Iterate over the faces and draw the vertices and normals
for i,j,k in mesh.faces:
a = L*mesh.verts[i]
b = L*mesh.verts[j]
c = L*mesh.verts[k]
na = L*N[i]-L0
nb = L*N[j]-L0
nc = L*N[k]-L0
drawLine(a, a+na)
drawLine(b, b+nb)
drawLine(c, c+nc)
def showUserNormals(mesh):
"""Draw normals given as "user normal N"/"uniform int Nfaces[3]".
"""
# Get the world transform to transform the local vertices and normals
# into the world coordinate system
L = mesh.worldtransform
L0 = L*vec3(0)
# Obtain the slot carrying the normals and the normal faces
N = mesh.geom.slot("N")
Nfaces = mesh.geom.slot("Nfaces")
# Iterate over the faces and normal faces...
for face, Nface in zip(mesh.faces, Nfaces):
i,j,k = face
ni,nj,nk = Nface
a = L*mesh.verts[i]
b = L*mesh.verts[j]
c = L*mesh.verts[k]
na = L*N[ni]-L0
nb = L*N[nj]-L0
nc = L*N[nk]-L0
drawLine(a, a+na)
drawLine(b, b+nb)
drawLine(c, c+nc)
######################################################################
# Load a scene file
load("bunny.3ds")
# Show its contents
listWorld()
# Draw the vertices & normals of every triangle mesh in the scene
for obj in scene.walkWorld():
# Check if the object is a triangle mesh
if isinstance(obj.geom, TriMeshGeom):
# Uncomment the following line to convert the normals from
# "user normal" to "varying normal"
# obj.geom = convMeshAttr(obj.geom, "N")
print 'Creating vertex markers for "%s"...'%obj.name
showVertices(obj)
print 'Creating normal lines for "%s"...'%obj.name
showNormals(obj)
# Visualizing the vertices and normals of a triangle mesh
#
# This script loads a scene and shows the vertices and normals of
# every mesh in the scene.
#
# Invoke the script via the viewer tool:
# $ viewer.py shownormals.py
######################################################################
def showVertices(mesh):
"""Draw markers at the vertex positions of a triangle mesh.
"""
# Vertices are stored in the local coordinate system of the geometry.
# But as we need the coordinates relative to the world coordinate
# system we have to obtain the transformation L that transforms from
# local to world coordinates.
L = mesh.worldtransform
# Iterate over the vertices and draw a marker at the global vertex
# position L*v.
for v in mesh.verts:
drawMarker(L*v, size=0.07, color=(0,0,1))
def showNormals(mesh):
"""Draw the normals as lines.
A normal is drawn at every vertex position. The normals may either be
specified as "varying normal N" or as "user normal N"/"uniform int Nfaces[3]".
The actual drawing code is in showVaryingNormals() and showUserNormals().
"""
# Check if there are normals available in this mesh
desc = mesh.findVariable("N")
if desc==None:
print 'Mesh "%s" has no normals set.'%mesh.name
return
# Unpack the variable descriptor
name, storage_class, type, mult = desc
# Are the normals stored as "varying normal N"?
if storage_class==VARYING and type==NORMAL and mult==1:
showVaryingNormals(mesh)
# Or are they stored as "user normal N"?
elif storage_class==USER and type==NORMAL and mult==1:
# Check if the normal faces are available
desc = mesh.findVariable("Nfaces")
if desc==None:
print 'Mesh "%s" has no normal faces set.'%mesh.name
else:
name, storage_class, type, mult = desc
if storage_class==UNIFORM and type==INT and mult==3:
# "N" and "Nfaces" is available and of the right type...
showUserNormals(mesh)
else:
print 'Mesh "%s": Invalid declaration of "Nfaces"'%mesh.name
else:
print 'Mesh "%s": Invalid declaration of variable "N".'%mesh.name
def showVaryingNormals(mesh):
"""Draw normals given as "varying normal N".
"""
# Get the world transform to transform the local vertices and normals
# into the world coordinate system
L = mesh.worldtransform
L0 = L*vec3(0)
# Obtain the slot carrying the normals
N = mesh.geom.slot("N")
# Iterate over the faces and draw the vertices and normals
for i,j,k in mesh.faces:
a = L*mesh.verts[i]
b = L*mesh.verts[j]
c = L*mesh.verts[k]
na = L*N[i]-L0
nb = L*N[j]-L0
nc = L*N[k]-L0
drawLine(a, a+na)
drawLine(b, b+nb)
drawLine(c, c+nc)
def showUserNormals(mesh):
"""Draw normals given as "user normal N"/"uniform int Nfaces[3]".
"""
# Get the world transform to transform the local vertices and normals
# into the world coordinate system
L = mesh.worldtransform
L0 = L*vec3(0)
# Obtain the slot carrying the normals and the normal faces
N = mesh.geom.slot("N")
Nfaces = mesh.geom.slot("Nfaces")
# Iterate over the faces and normal faces...
for face, Nface in zip(mesh.faces, Nfaces):
i,j,k = face
ni,nj,nk = Nface
a = L*mesh.verts[i]
b = L*mesh.verts[j]
c = L*mesh.verts[k]
na = L*N[ni]-L0
nb = L*N[nj]-L0
nc = L*N[nk]-L0
drawLine(a, a+na)
drawLine(b, b+nb)
drawLine(c, c+nc)
######################################################################
# Load a scene file
load("bunny.3ds")
# Show its contents
listWorld()
# Draw the vertices & normals of every triangle mesh in the scene
for obj in scene.walkWorld():
# Check if the object is a triangle mesh
if isinstance(obj.geom, TriMeshGeom):
# Uncomment the following line to convert the normals from
# "user normal" to "varying normal"
# obj.geom = convMeshAttr(obj.geom, "N")
print 'Creating vertex markers for "%s"...'%obj.name
showVertices(obj)
print 'Creating normal lines for "%s"...'%obj.name
showNormals(obj)