First question about this Roaming Ralph

I will just write down whole source code.

Author: Ryan Myers

Models: Jeff Styers, Reagan Heller

Last Updated: 6/13/2005

This tutorial provides an example of creating a character

and having it walk around on uneven terrain, as well

as implementing a fully rotatable camera.

import direct.directbase.DirectStart
from pandac.PandaModules import CollisionTraverser,CollisionNode
from pandac.PandaModules import CollisionHandlerQueue,CollisionRay
from pandac.PandaModules import Filename
from pandac.PandaModules import PandaNode,NodePath,Camera,TextNode
from pandac.PandaModules import Vec3,Vec4,BitMask32
from direct.gui.OnscreenText import OnscreenText
from import Actor
from direct.task.Task import Task
from direct.showbase.DirectObject import DirectObject
import random, sys, os, math

SPEED = 0.5

Figure out what directory this program is in.


Function to put instructions on the screen.

def addInstructions(pos, msg):
return OnscreenText(text=msg, style=1, fg=(1,1,1,1),
pos=(-1.3, pos), align=TextNode.ALeft, scale = .05)

Function to put title on the screen.

def addTitle(text):
return OnscreenText(text=text, style=1, fg=(1,1,1,1),
pos=(1.3,-0.95), align=TextNode.ARight, scale = .07)

class World(DirectObject):

def __init__(self):
    self.keyMap = {"left":0, "right":0, "forward":0, "cam-left":0, "cam-right":0},0,0,1))

    # Post the instructions

    self.title = addTitle("Panda3D Tutorial: Roaming Ralph (Walking on Uneven Terrain)")
    self.inst1 = addInstructions(0.95, "[ESC]: Quit")
    self.inst2 = addInstructions(0.90, "[Left Arrow]: Rotate Ralph Left")
    self.inst3 = addInstructions(0.85, "[Right Arrow]: Rotate Ralph Right")
    self.inst4 = addInstructions(0.80, "[Up Arrow]: Run Ralph Forward")
    self.inst6 = addInstructions(0.70, "[A]: Rotate Camera Left")
    self.inst7 = addInstructions(0.65, "[S]: Rotate Camera Right")
    # Set up the environment
    # This environment model contains collision meshes.  If you look
# in the egg file, you will see the following:
#    <Collide> { Polyset keep descend }
# This tag causes the following mesh to be converted to a collision
# mesh -- a mesh which is optimized for collision, not rendering.
# It also keeps the original mesh, so there are now two copies ---
# one optimized for rendering, one for collisions.  

    self.environ = loader.loadModel("models/world")      
    # Create the main character, Ralph

    ralphStartPos = self.environ.find("**/start_point").getPos()
    self.ralph = Actor("models/ralph",

    # Create a floater object.  We use the "floater" as a temporary
    # variable in a variety of calculations.
    self.floater = NodePath(PandaNode("floater"))

    # Accept the control keys for movement and rotation

    self.accept("escape", sys.exit)
    self.accept("arrow_left", self.setKey, ["left",1])
    self.accept("arrow_right", self.setKey, ["right",1])
    self.accept("arrow_up", self.setKey, ["forward",1])
    self.accept("a", self.setKey, ["cam-left",1])
    self.accept("s", self.setKey, ["cam-right",1])
    self.accept("arrow_left-up", self.setKey, ["left",0])
    self.accept("arrow_right-up", self.setKey, ["right",0])
    self.accept("arrow_up-up", self.setKey, ["forward",0])
    self.accept("a-up", self.setKey, ["cam-left",0])
    self.accept("s-up", self.setKey, ["cam-right",0])


    # Game state variables
    self.prevtime = 0
    self.isMoving = False

    # Set up the camera
    # We will detect the height of the terrain by creating a collision
    # ray and casting it downward toward the terrain.  One ray will
    # start above ralph's head, and the other will start above the camera.
    # A ray may hit the terrain, or it may hit a rock or a tree.  If it
    # hits the terrain, we can detect the height.  If it hits anything
    # else, we rule that the move is illegal.

    self.cTrav = CollisionTraverser()

    self.ralphGroundRay = CollisionRay()
    self.ralphGroundCol = CollisionNode('ralphRay')
    self.ralphGroundColNp = self.ralph.attachNewNode(self.ralphGroundCol)
    self.ralphGroundHandler = CollisionHandlerQueue()
    self.cTrav.addCollider(self.ralphGroundColNp, self.ralphGroundHandler)

    self.camGroundRay = CollisionRay()
    self.camGroundCol = CollisionNode('camRay')
    self.camGroundColNp =
    self.camGroundHandler = CollisionHandlerQueue()
    self.cTrav.addCollider(self.camGroundColNp, self.camGroundHandler)

    # Uncomment this line to see the collision rays
    #Uncomment this line to show a visual representation of the 
    #collisions occuring

#Records the state of the arrow keys
def setKey(self, key, value):
    self.keyMap[key] = value

# Accepts arrow keys to move either the player or the menu cursor,
# Also deals with grid checking and collision detection
def move(self, task):

    elapsed = task.time - self.prevtime

    # If the camera-left key is pressed, move camera left.
    # If the camera-right key is pressed, move camera right.
    camright =
    if (self.keyMap["cam-left"]!=0): - camright*(elapsed*20))
    if (self.keyMap["cam-right"]!=0): + camright*(elapsed*20))

    # save ralph's initial position so that we can restore it,
    # in case he falls off the map or runs into something.

    startpos = self.ralph.getPos()

    # If a move-key is pressed, move ralph in the specified direction.

    if (self.keyMap["left"]!=0):
        self.ralph.setH(self.ralph.getH() + elapsed*300)
    if (self.keyMap["right"]!=0):
        self.ralph.setH(self.ralph.getH() - elapsed*300)
    if (self.keyMap["forward"]!=0):
        backward = self.ralph.getNetTransform().getMat().getRow3(1)
        self.ralph.setPos(self.ralph.getPos() - backward*(elapsed*5))

    # If ralph is moving, loop the run animation.
    # If he is standing still, stop the animation.

    if (self.keyMap["forward"]!=0) or (self.keyMap["left"]!=0) or (self.keyMap["right"]!=0):
        if self.isMoving is False:
            self.isMoving = True
        if self.isMoving:
            self.isMoving = False

    # If the camera is too far from ralph, move it closer.
    # If the camera is too close to ralph, move it farther.

    camvec = self.ralph.getPos() -
    camdist = camvec.length()
    if (camdist > 10.0): + camvec*(camdist-10))
        camdist = 10.0
    if (camdist < 5.0): - camvec*(5-camdist))
        camdist = 5.0

    # Now check for collisions.


    # Adjust ralph's Z coordinate.  If ralph's ray hit terrain,
    # update his Z. If it hit anything else, or didn't hit anything, put
    # him back where he was last frame.

    entries = []
    for i in range(self.ralphGroundHandler.getNumEntries()):
        entry = self.ralphGroundHandler.getEntry(i)
    entries.sort(lambda x,y: cmp(y.getSurfacePoint(render).getZ(),
    if (len(entries)>0) and (entries[0].getIntoNode().getName() == "terrain"):

    # Keep the camera at one foot above the terrain,
    # or two feet above ralph, whichever is greater.
    entries = []
    for i in range(self.camGroundHandler.getNumEntries()):
        entry = self.camGroundHandler.getEntry(i)
    entries.sort(lambda x,y: cmp(y.getSurfacePoint(render).getZ(),
    if (len(entries)>0) and (entries[0].getIntoNode().getName() == "terrain"):[0].getSurfacePoint(render).getZ()+1.0)
    if ( < self.ralph.getZ() + 2.0): + 2.0)
    # The camera should look in ralph's direction,
    # but it should also try to stay horizontal, so look at
    # a floater which hovers above ralph's head.
    self.floater.setZ(self.ralph.getZ() + 2.0)

    # Store the task time and continue.
    self.prevtime = task.time
    return Task.cont

w = World()

I’m really sorry, but can you guys please explain me simply in step by step? I’m a newbie, so I don’t really understand anything except some for importing and camera positioning

Q1. How can I bind keys (E.G. W as a forward moving)to character?

Q2. In source code, he just wrote ‘starting position’. Don’t you have to specify where it starts?

Q3. How do I bind keys for camera rotation?

Q4. I don’t get some usual codes like ‘Self’ and how the words could do everything in Panda 3d. (E.G. getfullpath)

Really really sorry for wasting your valuable times, but I think that this is the way I could hear about other’s opinion and make it easier to understand.

Really really sorry.

Roving Ralf isn’t the best way to get started as it does a lot of things that should be learned one at the time.

The best set of tuts for beginners is the Hello World example in the manual and the following: (but you know about these I guess :wink:)

Q1. How can I bind keys (E.G. W as a forward moving)to character?
It is touched it there too: … rd-events/

Q2. In source code, he just wrote ‘starting position’. Don’t you have to specify where it starts?
There is a NodePath in the environment called start_point. The line below retrieve it from the scene graph.
ralphStartPos = self.environ.find("**/start_point").getPos()

Q3. How do I bind keys for camera rotation? … the_Camera

camera.setPos(camera, X, Y, Z) would give you a position relative to the camera local coordinates (Y is forward). What is done in this code isn’t beginner’s stuff unless you are comfortable with 3d math.

Q4. I don’t get some usual codes like ‘Self’ and how the words could do everything in Panda 3d. (E.G. getfullpath)
self is a python thing, the Python tutorials on classes is here.

I don’t understand the second part of the question, however.

Hope this helps, even if it isn’t exactly what you were looking for.

O that was fast!

I would never expect that fast answer in realityfactory forum…

Anyway, key binding helped a lot in understanding how to basic FPS controls, and again thanks for helping.

2nd question was actually asking about if there’s already a starting point somewhere in the background.

Again, thanks a million!

The start position is an empty mesh called start_point the author created in the modeler when he/she modeled the terrain.
Using the find("**/start_point").getPos() method the author extracts the position of the starting point as created in the modeler.