Function to find the normal (or angle) of a face of any model

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eat much pie

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Posted: 3rd May 2004 18:28 Edited at: 19th May 2004 20:05

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After much pain and struggle (of about 4 hours) I've come up with the code to find the normal of a face. It uses intersect object, so there are some limitations to its use (ie. you can't scale the object to which the face belongs).
Just type in the syntax as you would with intersect object, and the normal data will be stored in the second 3d vector, so to access it, you need to:
YourVariableX#=x vector(2)
YourVariableY#=y vector(2)
YourVariableZ#=z vector(2)

Put the following code at the beginning of the program:

+ Code Snippet

make object cube 30,0
make object cube 31,0
make object cube 32,0
null = make vector3(1)
null = make vector3(2)

Put the following code with all your other functions or gosubs:

function normals(obj,x#,y#,z#,endx#,endy#,endz#)

position object 30,x#,y#,z#
point object 30,endx#,endy#,endz#

position object 31,object position x(30),object position y(30),object position z(30)
set object to object orientation 31,30
move object up 31,0.1

position object 32,object position x(30),object position y(30),object position z(30)
set object to object orientation 32,30
move object right 32,0.1

x1#=object position x(30)
x2#=object position x(31)
x3#=object position x(32)

y1#=object position y(30)
y2#=object position y(31)
y3#=object position y(32)

z1#=object position z(30)
z2#=object position z(31)
z3#=object position z(32)

set vector3 1,0,0,0
set vector3 2,0,0,0

set vector3 1,x2#-x1#,y2#-y1#,z2#-z1#
set vector3 2,x3#-x1#,y3#-y1#,z3#-z1#

col=0

for t=0 to 2
if t=0 then k#=intersect object(obj,object position x(30+t),object position y(30+t),object position z(30+t),endx#,endy#,endz#):dist#=k#
if t=1 then k#=intersect object(obj,object position x(30+t),object position y(30+t),object position z(30+t),endx#+x vector3(1),endy#+y vector3(1),endz#+z vector3(1))
if t=2 then k#=intersect object(obj,object position x(30+t),object position y(30+t),object position z(30+t),endx#+x vector3(2),endy#+y vector3(2),endz#+z vector3(2))
move object 30+t,k#
if k#>0 then col=col+1
next t

if col=3

x1#=object position x(30)
x2#=object position x(31)
x3#=object position x(32)

y1#=object position y(30)
y2#=object position y(31)
y3#=object position y(32)

z1#=object position z(30)
z2#=object position z(31)
z3#=object position z(32)

xvec1#=x2#-x1#
xvec2#=x3#-x1#
yvec1#=y2#-y1#
yvec2#=y3#-y1#
zvec1#=z2#-z1#
zvec2#=z3#-z1#

set vector3 1,xvec1#,yvec1#,zvec1#
set vector3 2,xvec2#,yvec2#,zvec2#

cross product vector3 2, 1, 2

normalize vector3 2,2

endif

endfunction dist#

+ Code Snippet

function normals(obj,x#,y#,z#,endx#,endy#,endz#)




position object 30,x#,y#,z#
point object 30,endx#,endy#,endz#

position object 31,object position x(30),object position y(30),object position z(30)
set object to object orientation 31,30
move object up 31,0.1

position object 32,object position x(30),object position y(30),object position z(30)
set object to object orientation 32,30
move object right 32,0.1

x1#=object position x(30)
x2#=object position x(31)
x3#=object position x(32)

y1#=object position y(30)
y2#=object position y(31)
y3#=object position y(32)

z1#=object position z(30)
z2#=object position z(31)
z3#=object position z(32)

set vector3 1,0,0,0
set vector3 2,0,0,0

set vector3 1,x2#-x1#,y2#-y1#,z2#-z1#
set vector3 2,x3#-x1#,y3#-y1#,z3#-z1#

col=0

for t=0 to 2
if t=0 then k#=intersect object(obj,object position x(30+t),object position y(30+t),object position z(30+t),endx#,endy#,endz#):dist#=k#
if t=1 then k#=intersect object(obj,object position x(30+t),object position y(30+t),object position z(30+t),endx#+x vector3(1),endy#+y vector3(1),endz#+z vector3(1))
if t=2 then k#=intersect object(obj,object position x(30+t),object position y(30+t),object position z(30+t),endx#+x vector3(2),endy#+y vector3(2),endz#+z vector3(2))
move object 30+t,k#
if k#>0 then col=col+1
next t

if col=3

x1#=object position x(30)
x2#=object position x(31)
x3#=object position x(32)

y1#=object position y(30)
y2#=object position y(31)
y3#=object position y(32)

z1#=object position z(30)
z2#=object position z(31)
z3#=object position z(32)

xvec1#=x2#-x1#
xvec2#=x3#-x1#
yvec1#=y2#-y1#
yvec2#=y3#-y1#
zvec1#=z2#-z1#
zvec2#=z3#-z1#

set vector3 1,xvec1#,yvec1#,zvec1#
set vector3 2,xvec2#,yvec2#,zvec2#

cross product vector3 2, 1, 2

normalize vector3 2,2

endif

endfunction dist#

NB: this function will return the distance between start point and collision point (the same as interect object).

http://www.nuclearglory.com/?i=453288050 , AMAZING COLLISION SYSTEM!

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French gui

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Joined: 11th May 2004

Location: France

Posted: 21st May 2004 02:53

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Very good, it's helping me a lot for my mini golf game. Don't know why I'm only the first to post a message 'cos your snippet's very cool...

My English is not so good I'm just French

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eat much pie

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Location: Within the mind of a lowly mortal...

Posted: 22nd May 2004 16:09 Edited at: 22nd May 2004 16:11

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Je l'ai fait sans les objets!

Cough...

Anyway, I've just finished the second version of my normals finding function, in which there are no objects at all! I used triganometry and vectors instead! Oh, and if you release a game that uses my function, please give credit to me in the credits.

put this before the main loop

+ Code Snippet


null = make vector3(1)
null = make vector3(2)

put this with all your other funcitons or 'gosubs'

function normals(obj,x#,y#,z#,endx#,endy#,endz#)

set vector3 1,0,0,0
set vector3 2,0,0,0

yrotate#=atanfull(endx#-x#,endz#-z#)
xrotate#=atanfull(endz#-z#,endy#-y#)

set vector3 1,sin(yrotate#),-sin(wrapvalue(xrotate#+90)),cos(yrotate#)
normalize vector3 1,1

x2#=x#+x vector3(1)
y2#=y#+y vector3(1)
z2#=z#+z vector3(1)

set vector3 1,sin(wrapvalue(90+yrotate#))*cos(xrotate#),0,cos(wrapvalue(90+yrotate#))*cos(xrotate#)
normalize vector3 1,1

x3#=x#+x vector3(1)
y3#=y#+y vector3(1)
z3#=z#+z vector3(1)

set vector3 2,endx#-x#,endy#-y#,endz#-z#

mydist1#=intersect object(obj,x#,y#,z#,endx#,endy#,endz#)
mydist2#=intersect object(obj,x2#,y2#,z2#,x2#+x vector3(2),y2#+y vector3(2),z2#+z vector3(2))
mydist3#=intersect object(obj,x3#,y3#,z3#,x3#+x vector3(2),y3#+y vector3(2),z3#+z vector3(2))

if mydist1#=0 or mydist2#=0 or mydist3#=0 then set vector3 1,0,0,0:set vector3 2,0,0,0

if mydist1#>0 and mydist2#>0 and mydist3#>0

normalize vector3 2,2

endx1#=(x vector3(2)*mydist1#)+x#
endy1#=(y vector3(2)*mydist1#)+y#
endz1#=(z vector3(2)*mydist1#)+z#

endx2#=(x vector3(2)*mydist2#)+x2#
endy2#=(y vector3(2)*mydist2#)+y2#
endz2#=(z vector3(2)*mydist2#)+z2#

endx3#=(x vector3(2)*mydist3#)+x3#
endy3#=(y vector3(2)*mydist3#)+y3#
endz3#=(z vector3(2)*mydist3#)+z3#

xvec1#=endx2#-endx1#
xvec2#=endx3#-endx1#
yvec1#=endy2#-endy1#
yvec2#=endy3#-endy1#
zvec1#=endz2#-endz1#
zvec2#=endz3#-endz1#

set vector3 1,xvec1#,yvec1#,zvec1#
set vector3 2,xvec2#,yvec2#,zvec2#

cross product vector3 2, 1, 2

normalize vector3 2,2

set vector3 2,-x vector3(2),-y vector3(2),-z vector3(2)

endif

endfunction mydist1#

+ Code Snippet


function normals(obj,x#,y#,z#,endx#,endy#,endz#)

set vector3 1,0,0,0
set vector3 2,0,0,0


yrotate#=atanfull(endx#-x#,endz#-z#)
xrotate#=atanfull(endz#-z#,endy#-y#)


set vector3 1,sin(yrotate#),-sin(wrapvalue(xrotate#+90)),cos(yrotate#)
normalize vector3 1,1

x2#=x#+x vector3(1)
y2#=y#+y vector3(1)
z2#=z#+z vector3(1)

set vector3 1,sin(wrapvalue(90+yrotate#))*cos(xrotate#),0,cos(wrapvalue(90+yrotate#))*cos(xrotate#)
normalize vector3 1,1

x3#=x#+x vector3(1)
y3#=y#+y vector3(1)
z3#=z#+z vector3(1)

set vector3 2,endx#-x#,endy#-y#,endz#-z#


mydist1#=intersect object(obj,x#,y#,z#,endx#,endy#,endz#)
mydist2#=intersect object(obj,x2#,y2#,z2#,x2#+x vector3(2),y2#+y vector3(2),z2#+z vector3(2))
mydist3#=intersect object(obj,x3#,y3#,z3#,x3#+x vector3(2),y3#+y vector3(2),z3#+z vector3(2))


if mydist1#=0 or mydist2#=0 or mydist3#=0 then set vector3 1,0,0,0:set vector3 2,0,0,0

if mydist1#>0 and mydist2#>0 and mydist3#>0

normalize vector3 2,2

endx1#=(x vector3(2)*mydist1#)+x#
endy1#=(y vector3(2)*mydist1#)+y#
endz1#=(z vector3(2)*mydist1#)+z#

endx2#=(x vector3(2)*mydist2#)+x2#
endy2#=(y vector3(2)*mydist2#)+y2#
endz2#=(z vector3(2)*mydist2#)+z2#

endx3#=(x vector3(2)*mydist3#)+x3#
endy3#=(y vector3(2)*mydist3#)+y3#
endz3#=(z vector3(2)*mydist3#)+z3#


xvec1#=endx2#-endx1#
xvec2#=endx3#-endx1#
yvec1#=endy2#-endy1#
yvec2#=endy3#-endy1#
zvec1#=endz2#-endz1#
zvec2#=endz3#-endz1#

set vector3 1,xvec1#,yvec1#,zvec1#
set vector3 2,xvec2#,yvec2#,zvec2#

cross product vector3 2, 1, 2

normalize vector3 2,2

set vector3 2,-x vector3(2),-y vector3(2),-z vector3(2)

endif

endfunction mydist1#

To use the Normals data:

+ Code Snippet

YourVariableX# = x vector3(2)
YourVariableY# = y vector3(2)
YourVariableZ# = z vector3(2)

If anyone has any questions, feel free to ask. I check the forums every day.

http://www.nuclearglory.com/?i=453288050 : Nuclear Glory, AMAZING COLLISION SYSTEM!

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eat much pie

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Joined: 9th Apr 2004

Location: Within the mind of a lowly mortal...

Posted: 22nd May 2004 16:17 Edited at: 22nd May 2004 16:31

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To use my command, use it as you would with the intersect object command, so let's say you want to find out the normals data of a plane belonging to a 'castle' that a bullet went through (starting from the camera position).

+ Code Snippet

oldx#=camera position x()
oldy#=camera position y()
oldz#=camera position z()

newx#=object position x(bullet)
newy#=object position y(bullet)
newz#=object position z(bullet)

dist#=normals(castle,oldx#,oldy#,oldz#,newx#,newy#,newz#)

that does the calculating, then let's say you want to put a bullet hole where the bullet and castle collided:

+ Code Snippet

position object BULLET_HOLE,oldx#,oldy#,oldz#
point object BULLET_HOLE,newx#,newy#,newz#

move object BULLET_HOLE,dist#

embossX#=object position x(BULLET_HOLE)+x vector(2)
embossY#=object position y(BULLET_HOLE)+y vector(2)
embossZ#=object position z(BULLET_HOLE)+z vector(2)

point object BULLET_HOLE,embossX#,embossY#,embossZ#

And voila! the bullet hole is rotated and positioned at the right values!

NB. You could use maths to figure out the collided positoin as opposed to using an object, but I really can't be bothered to explain it to you at the moment. If you want me to explain how to do it, just let me know.

http://www.nuclearglory.com/?i=453288050 : Nuclear Glory, AMAZING COLLISION SYSTEM!

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Code Snippets / Function to find the normal (or angle) of a face of any model