Using ModelsUnderRay Collision detection

Question

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
http://www.fbe.unsw.edu.au/learning/director/,
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

Answer 1

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?