Using ModelsUnderRay Collision detection

[Roofy]

Ok first things first. I know you guys who have been reading my other post is
going to get confused after reading this post so let me make myself clear.
First yes I was previously trying to Havok, but I could not get my car to work
with it. So This is why I am now asking stuff about ModelsUnderRay collision
detection.

Second, I found this tutorial at
[url]http://www.fbe.unsw.edu.au/learning/director/[/url], and all things seem to go pretty
good with using the max File the tutorial uses. Meaning I have not tried this
on my car as of yet. In addition, considering that things seem to work with the
tutorial, I now came up with a new question. Basically, if I am correct, I
think by using the code below, this is not going to work with my car when the
car is going up a hill. I conclude this by knowing that the tutorial just uses
a character, meaning it is not like a using something like a car that has a
chassis and 4 wheels. So my question is this... How can I get the chassis to
follow the angle of the hill if I am using a behaviour that looks something
like this...

on collisionDetect me

-- create a list to store collision data created by modelsUnderRay
-- cast ray to left
collisionList = p3Dmember.modelsUnderRay(pCharacter.worldPosition, \
-pCharacter.transform.yAxis,#detailed)

-- if models picked up by ray, then activate checkForCollion
-- handler and send the collisionList as a parameter
if (collisionList.count) then me.checkForCollision(collisionList[1])

-- cast ray to right
collisionList = p3Dmember.modelsUnderRay(pCharacter.worldPosition, \
pCharacter.transform.yAxis,#detailed)

-- if models picked up by ray, then check for collision
if (collisionList.count) then me.checkForCollision(collisionList[1])

-- cast ray forward
collisionList = p3Dmember.modelsUnderRay(pCharacter.worldPosition, \
pCharacter.transform.xAxis,#detailed)

-- if models picked up by ray, then check for collision
if (collisionList.count) then me.checkForCollision(collisionList[1])

-- cast ray backward
collisionList = p3Dmember.modelsUnderRay(pCharacter.worldPosition, \
-pCharacter.transform.xAxis,#detailed)

-- if models picked up by ray, then check for collision
if (collisionList.count) then me.checkForCollision(collisionList[1])

end


on checkForCollision me, collisData

-- grab the #distance value from the CollisionList
dist = collisData.distance

-- check if distance is less than width of bounding box
if (dist < pCharBoundingBox.resource.width ) then

-- get distance of penetration
diff = pCharBoundingBox.resource.width - dist

-- calculate vector perpendicular to the wall's surface to move the
character
-- using the #isectNormal property
tVector = collisData.isectNormal * diff

-- move the character in order to resolve the collision
pCharacter.translate(tVector,#world)

end if

end


on keyDown

-- check to see which key has been pressed
-- and set the property relating to that key to TRUE
if keypressed(123) then pLeftArrow = TRUE -- 123 = left arrow key
if keypressed(124) then pRightArrow = TRUE -- 124 = right arrow key
if keypressed(125) then pDownArrow = TRUE -- 125 = down arrow key
if keypressed(126) then pUpArrow = TRUE -- 125 = up arrow key

-- if 'r' key pressed, return character to starting position
if keypressed("r") then resetCharacter

-- if 'c' key is pressed, then switch camera
if keypressed("c") then changeCamera

end


on keyUp
-- when the arrow keys are released, set the properties to FALSE
pLeftArrow = FALSE
pRightArrow = FALSE
pUpArrow = FALSE
pDownArrow = FALSE
end


on exitFrame
characterMove
end


on characterMove

-- if the right arrow is pressed,
-- rotate the character 5 degrees about the z-axis
if pRightArrow then pCharacter.rotate(0,0,-5)

--if the right arrow is pressed,
-- rotate character -5 degrees about the z-axis
if pLeftArrow then pCharacter.rotate(0,0,5)

-- if the up arrow is pressed,
-- move the character 5 pixels along the y-axis
if pUpArrow then pCharacter.translate(0,5,0)

-- if the down arrow is pressed,
-- move the character -5 pixels along the y-axis
if pDownArrow then pCharacter.translate(0,-5,0)


-- move along terrain
-- create reference for terrain (ground)
terrain = p3Dmember.model("Terrain")

-- store character's position
charPos = pCharacter.worldPosition
charPos.y = charPos.y - 20

-- cast a ray down
collisData = p3Dmember.modelsUnderRay(charPos,vector(0,0,-1),#detailed)

-- if model is picked up on ray.
if collisData.count then

-- store total no of models detected by the ray
totalCount = collisData.count

repeat with modelNo = 1 to totalCount

-- check if over the terrain model
if (collisData[modelNo].model = terrain) then

terrainPos = collisData[modelNo].isectPosition

-- find out the distance the character should move up or down
diff = (terrainPos.z - pCharacter.worldPosition.z)+45

-- move the character
pCharacter.translate(0,0,diff,#world)


end if

end repeat

end if

end

[Roofy]

ok,
I have been trying to work this out for ahwile and I got pretty close on
getting this correct but there are still some glitches. So far I did a little
research in the help files to see what the dot product does and this is how I
got my calculations going so far

--the code
on beginSprite me
I created 2 spheres and a box. Next, I then positioned them so that the first
sphere is alligned with the front end of the box and then I aligned the second
sphere to back of the box. I will not show you the code of beginSprite because
all this does is for creating the models and there are no calculations going
inside this handler. In addition, with these 3 models, my purpose is to say
lets prtend that the box is the chasis of the car and the sphere that is placed
at the frent end of the chassis are to represemt the 2 front wheels and the
othere sphere is to represent the 2 back wheels of the car. Also, I initlalised
a timer to the following below
pTimer = (the milliseconds)
end beginSprite
... note The timere is just for purposes of simulating a pretend upward
movement for the wheels. See below which should explain it better then I can
say it in words.

--the code below is the calculations. The translations is for saying that I am
pretending that the wheels are inclining up a hill. However, the wheels in the
true game will be getting calculated by finding the distance of collion by
using the modelsUnderRay function just like you normally would. By the way, all
models and the camera are set to y is the up vector

on exitFrame
if ((the milliseconds) - pTimer) > 1000 then -- increment the calculations
every one second
pBall1.translate(0, 0.125, 0) -- This is for saying that this is the
calculations that I am calculating the front wheels need to move up when they
incline up the hill.
pBall2.translate(0, -0.125, 0) -- Just like the front wheel pretend
calulations but for the back wheels, and use a negative translate.
pos1 = pBall1.transform.position -- get the calculated position for the
front wheels
pos2 = pBall2.transform.position -- get the calculated position for the back
wheels
norm1 = pos1.getnormalized() -- not sure I understand this, but in the help
files, it says that when you calculate the dot product of 2 vectors that have
been normalized, you then get their cosine
norm2 = pos2.getNormalized() -- normalize the back wheels position
dotProduct = norm1.dot(norm2) -- calculate the dot product of the 2 vectors
pBox.rotate(dotAngle, 0, 0) -- I took a guess and thought that using the
dotProduct will allow me to correctly rotate the chassis but the chassis is
quite not rotating correctlly
pTimer = (the milliseconds) -- update the timer so that we can recyle the
above code again
end if
end exitFrame

... Ok, now like I said previously, the chassis is rotating almost correctlly,
but if you continue to do this, and by after the third cycle, the front end
wheels start to collide with the chassis. So in other words, the rotations look
correct untill exitFrame is called for the third time and after which then the
front wheels start to collide with the chassis.

So I am wondering if anyone could help me out to fix this and explain what I
am doing wrong?