WorldViz User Forum - Snake slithering... how to accomplish this in Vizard?

Hi,

You could still use a hand-animation and simply rotate the snake so that it is perpendicular to the normal of the terrain it is on. However, this will only work on terrain with gradual height changes.

Vizard allows you to take control of individual avatar bones. So you could manually animate the snake and use intersection tests to keep it above the terrain.

I made a script a while back that simulates a snake moving, but only in 2D. The snake will follow the mouse cursor. You could perform a similar technique, except make sure that each new location is above the terrain. The snake does not check for collisions between itself though. Here is the code, hope it helps:

Code:

import viz

viz.go()



class Snake(object):

        

        def __init__(self,num=50,skin=None,speed=0.1,turnSpeed=420.0,step=10):

                

                self.__buffer = [(0.0,[0.5,0.5,0],0.0)]

                self.__body = []                                #List of body parts

                self.__step = step                                #Step time between each body

                self.__speed = speed                        #Movement speed

                self.__turnSpeed = turnSpeed        #Maximum turn speed

                self.__bufsize = 500                        #Size of position buffer

                self.__skin = skin                                #Skin texture



                #Add initial elements

                for x in xrange(num):

                        self.addBody()

                        

        def updateMouse(self,elapsed):

                

                #Get current mouse position

                pos = viz.mouse.getPosition(immediate=True)

                

                #If position is too close from previous, then stop

                if vizmat.Distance(pos+[0],self.__buffer[0][1]+[0]) < 0.01:

                        return

                

                #Compute angle to mouse position

                angle = vizmat.AngleToPoint(self.__buffer[0][1],pos)

                

                #Make sure turn speed does not exceed max turn speed

                diff = vizmat.AngleDiff(self.__buffer[0][2],angle)

                maxDiff = elapsed * self.__turnSpeed

                if abs(diff) > maxDiff:

                        angle = self.__buffer[0][2] + (viz.sign(diff) * maxDiff)

                

                #Compute matrix for new position

                mat = viz.Matrix.axisangle(0,0,-1,angle)

                mat.setPosition(self.__buffer[0][1])

                mat.preTrans(0,self.__speed*elapsed,0)

                

                #Add position to buffer

                self.__buffer.insert(0,(viz.getFrameTime(),mat.getPosition(),angle))

                if len(self.__buffer) > self.__bufsize:

                        self.__buffer.pop()

                

                self.updateStepSample()

                        

        def updateStepSample(self):

                

                size = len(self.__buffer)-1

                

                for i,b in enumerate(self.__body):

                        

                        sample = min(self.__step * i,size)



                        b.setPosition(self.__buffer[sample][1])

                        b.setAxisAngle(0,0,-1,self.__buffer[sample][2])



        def addBody(self):

                b = viz.addTexQuad(viz.SCREEN,size=30,texture=self.__skin)

                b.drawOrder(-len(self.__body))

                self.__body.append(b)

                

s = Snake(skin=viz.add('radio_up.gif'))



def UpdateSnake():

        s.updateMouse(viz.elapsed())

vizact.ontimer(0,UpdateSnake)