In an effort to learn more about ODE/Panda3D and as an assistance for debugging ODE simulation, I am writing a few Python classes that will let me visualize what is happening. Primarily, I want a way to see the ODE Geoms and since I can find no way to debug view these, I decided to start work on a Python implementation.

This, of course, probably would normally live in the C++ part of Panda3D, but I am nowhere near ready to start tackling that right now.

Hereâ€™s what I got so far: A class for to generate GeomNode representations of ODE geoms.

Maybe other people will find this useful. Comments/suggestions are always welcome, as I am still learning Panda3d.

```
import direct.directbase.DirectStart
from pandac.PandaModules import Point3, Vec3
from pandac.PandaModules import GeomVertexFormat, GeomVertexData, GeomVertexWriter
from pandac.PandaModules import Geom, GeomNode, GeomPoints, NodePath, GeomLinestrips
import math
"""
Note that wireprims are wire-like representations of geom, in the same manner as Ogre's debug mode. I find this the most useful way to represent
ODE geom structures visually, as you can clearly see the orientation versus a more generic wireframe mesh.
These wireprims are rendered as linestrips. Therefore, only vertices are required and texturing is not supported. You can use standard render attribute changes such
as setColor in order to change the line's color. By default it is green.
This class merely returns a NodePath to a GeomNode that is a representation of what is requested. You can use this outside of ODE geom visualizations, obviously.
Supported are sphere, box, cylinder, capsule (aka capped cylinder), ray, and plane
to use:
sphereNodepath = wireGeom().generate ('sphere', radius=1.0)
boxNodepath = wireGeom().generate ('box', extents=(1, 1, 1))
cylinderNodepath = wireGeom().generate ('cylinder', radius=1.0, length=3.0)
rayNodepath = wireGeom().generate ('ray', length=3.0)
planeNodepath = wireGeom().generate ('plane')
"""
class wireGeom:
def __init__ (self):
# GeomNode to hold our individual geoms
self.gnode = GeomNode ('wirePrim')
# How many times to subdivide our spheres/cylinders resulting vertices. Keep low
# because this is supposed to be an approximate representation
self.subdiv = 12
def line (self, start, end):
# since we're doing line segments, just vertices in our geom
format = GeomVertexFormat.getV3()
# build our data structure and get a handle to the vertex column
vdata = GeomVertexData ('', format, Geom.UHStatic)
vertices = GeomVertexWriter (vdata, 'vertex')
# build a linestrip vertex buffer
lines = GeomLinestrips (Geom.UHStatic)
vertices.addData3f (start[0], start[1], start[2])
vertices.addData3f (end[0], end[1], end[2])
lines.addVertices (0, 1)
lines.closePrimitive()
geom = Geom (vdata)
geom.addPrimitive (lines)
# Add our primitive to the geomnode
self.gnode.addGeom (geom)
def circle (self, radius, axis, offset):
# since we're doing line segments, just vertices in our geom
format = GeomVertexFormat.getV3()
# build our data structure and get a handle to the vertex column
vdata = GeomVertexData ('', format, Geom.UHStatic)
vertices = GeomVertexWriter (vdata, 'vertex')
# build a linestrip vertex buffer
lines = GeomLinestrips (Geom.UHStatic)
for i in range (0, self.subdiv):
angle = i / float(self.subdiv) * 2.0 * math.pi
ca = math.cos (angle)
sa = math.sin (angle)
if axis == "x":
vertices.addData3f (0, radius * ca, radius * sa + offset)
if axis == "y":
vertices.addData3f (radius * ca, 0, radius * sa + offset)
if axis == "z":
vertices.addData3f (radius * ca, radius * sa, offset)
for i in range (1, self.subdiv):
lines.addVertices(i - 1, i)
lines.addVertices (self.subdiv - 1, 0)
lines.closePrimitive()
geom = Geom (vdata)
geom.addPrimitive (lines)
# Add our primitive to the geomnode
self.gnode.addGeom (geom)
def capsule (self, radius, length, axis):
# since we're doing line segments, just vertices in our geom
format = GeomVertexFormat.getV3()
# build our data structure and get a handle to the vertex column
vdata = GeomVertexData ('', format, Geom.UHStatic)
vertices = GeomVertexWriter (vdata, 'vertex')
# build a linestrip vertex buffer
lines = GeomLinestrips (Geom.UHStatic)
# draw upper dome
for i in range (0, self.subdiv / 2 + 1):
angle = i / float(self.subdiv) * 2.0 * math.pi
ca = math.cos (angle)
sa = math.sin (angle)
if axis == "x":
vertices.addData3f (0, radius * ca, radius * sa + (length / 2))
if axis == "y":
vertices.addData3f (radius * ca, 0, radius * sa + (length / 2))
# draw lower dome
for i in range (0, self.subdiv / 2 + 1):
angle = -math.pi + i / float(self.subdiv) * 2.0 * math.pi
ca = math.cos (angle)
sa = math.sin (angle)
if axis == "x":
vertices.addData3f (0, radius * ca, radius * sa - (length / 2))
if axis == "y":
vertices.addData3f (radius * ca, 0, radius * sa - (length / 2))
for i in range (1, self.subdiv + 1):
lines.addVertices(i - 1, i)
lines.addVertices (self.subdiv + 1, 0)
lines.closePrimitive()
geom = Geom (vdata)
geom.addPrimitive (lines)
# Add our primitive to the geomnode
self.gnode.addGeom (geom)
def rect (self, width, height, axis):
# since we're doing line segments, just vertices in our geom
format = GeomVertexFormat.getV3()
# build our data structure and get a handle to the vertex column
vdata = GeomVertexData ('', format, Geom.UHStatic)
vertices = GeomVertexWriter (vdata, 'vertex')
# build a linestrip vertex buffer
lines = GeomLinestrips (Geom.UHStatic)
# draw a box
if axis == "x":
vertices.addData3f (0, -width, -height)
vertices.addData3f (0, width, -height)
vertices.addData3f (0, width, height)
vertices.addData3f (0, -width, height)
if axis == "y":
vertices.addData3f (-width, 0, -height)
vertices.addData3f (width, 0, -height)
vertices.addData3f (width, 0, height)
vertices.addData3f (-width, 0, height)
if axis == "z":
vertices.addData3f (-width, -height, 0)
vertices.addData3f (width, -height, 0)
vertices.addData3f (width, height, 0)
vertices.addData3f (-width, height, 0)
for i in range (1, 3):
lines.addVertices(i - 1, i)
lines.addVertices (3, 0)
lines.closePrimitive()
geom = Geom (vdata)
geom.addPrimitive (lines)
# Add our primitive to the geomnode
self.gnode.addGeom (geom)
def generate (self, type, radius=1.0, length=1.0, extents=Point3(1, 1, 1)):
if type == 'sphere':
# generate a simple sphere
self.circle (radius, "x", 0)
self.circle (radius, "y", 0)
self.circle (radius, "z", 0)
if type == 'capsule':
# generate a simple capsule
self.capsule (radius, length, "x")
self.capsule (radius, length, "y")
self.circle (radius, "z", -length / 2)
self.circle (radius, "z", length / 2)
if type == 'box':
# generate a simple box
self.rect (extents[1], extents[2], "x")
self.rect (extents[0], extents[2], "y")
self.rect (extents[0], extents[1], "z")
if type == 'cylinder':
# generate a simple cylinder
self.line ((0, -radius, -length / 2), (0, -radius, length/2))
self.line ((0, radius, -length / 2), (0, radius, length/2))
self.line ((-radius, 0, -length / 2), (-radius, 0, length/2))
self.line ((radius, 0, -length / 2), (radius, 0, length/2))
self.circle (radius, "z", -length / 2)
self.circle (radius, "z", length / 2)
if type == 'ray':
# generate a ray
self.circle (length / 10, "x", 0)
self.circle (length / 10, "z", 0)
self.line ((0, 0, 0), (0, 0, length))
self.line ((0, 0, length), (0, -length/10, length*0.9))
self.line ((0, 0, length), (0, length/10, length*0.9))
if type == 'plane':
# generate a plane
length = 3.0
self.rect (1.0, 1.0, "z")
self.line ((0, 0, 0), (0, 0, length))
self.line ((0, 0, length), (0, -length/10, length*0.9))
self.line ((0, 0, length), (0, length/10, length*0.9))
# rename ourselves to wirePrimBox, etc.
name = self.gnode.getName()
self.gnode.setName(name + type.capitalize())
NP = NodePath (self.gnode) # Finally, make a nodepath to our geom
NP.setColor(0.0, 1.0, 0.0) # Set default color
return NP
# demonstration code below
allGeoms = render.attachNewNode ("allWireGeoms")
plane = wireGeom().generate ('plane')
plane.setPos (0, 0, 0)
plane.setHpr (0, 0, 0)
plane.reparentTo( allGeoms )
sphere = wireGeom().generate ('sphere', radius=1.0)
sphere.setPos (0, 3, 1)
sphere.setHpr (0, 0, 0)
sphere.reparentTo( allGeoms )
capsule = wireGeom().generate ('capsule', radius=1.0, length=3.0)
capsule.setPos (0, 6, 1)
capsule.setHpr (0, 0, 0)
capsule.reparentTo( allGeoms )
box = wireGeom().generate ('box', extents=(1, 1, 1))
box.setPos (0, 9, 1)
box.setHpr (0, 0, 0)
box.reparentTo( allGeoms )
cylinder = wireGeom().generate ('cylinder', radius=1.0, length=3.0)
cylinder.setPos (0, -3, 1)
cylinder.setHpr (0, 0, 0)
cylinder.reparentTo( allGeoms )
ray = wireGeom().generate ('ray', length=3.0)
ray.setPos (0, -6, 1)
ray.setHpr (0, 0, 0)
ray.reparentTo( allGeoms )
allGeoms.reparentTo( base.render )
# Set the camera position
base.disableMouse()
base.camera.setPos(40, 0, 0)
base.camera.lookAt(0, 0, 0)
# Spin all of the wireGeoms around so you can see 'em
i = allGeoms.hprInterval (4.0, Vec3(360, 360, 0))
i.loop()
run()
```