Snake slithering... how to accomplish this in Vizard?

[k_iwan]

Hi,

I am going to have snake slithering animations onto a terrain.
For the rigging process I will make the bone to be as close as possible onto the abdoment-ground.

Could someone suggest a method of animating snake in vizard to make it realistic? By doing hand-animation the snake would be half-floating onto a slope terrain.

Is there a way to tell vizard to have bone1,...bone10 to always at a certain distance from the ground / object with collision detection enabled?

Is there a way to apply a mathematical formula (sin or Cos) onto the entire bone structure in vizard to produce a more realistic slithering animation?


Thank you,

Iwan

[farshizzo]

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:

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)

[k_iwan]

Hi Farshizzo,

I will look into it. Thanks for the hint.

Kind Regards,
Iwan

[k_iwan]

Hi,

I took this example from Punching demo, line 169

walkTo = enemy.walkto(headPos[0],terrain,headPos[2],vizmat.GetRandom(MIN_SPEED,MAX_SPEED),260,2)

..and the avatar walk on the terrain! Which puzzles me, the second argument "terrain", where did it come from? terrain = viz.add('xxx')?


Kind Regards,
Iwan

[farshizzo]

Hi,

The y value of the walkto action can optionally be a node object. When this is the case the avatar will adjust its y position to be on top of the node. This is useful when you want the avatar to walk on a non-flat terrain.

[k_iwan]

Noted! is this documented? probably I missed it.
Thank you.