What is“|” mean?

Farabi · February 23, 2012, 12:27:08 PM

|U| |V|

I wonder what is that mean.

qWord · February 23, 2012, 12:39:37 PM

?
maybe the vector length?
e.g. |U| is the length of vector U.

dedndave · February 23, 2012, 01:55:29 PM

absolute value:
it means - if it's negative, multiply it by -1
so - yah, vector length :P

vanjast · February 24, 2012, 08:41:59 AM

The formula Y= |U| |V| as it stands means

If U < 0 then
U = -U
Else
U = U (if this makes sense :green2)
endif

So Y = Abs(U) * Abs(V) >= 0

In correct Vector maths notation |U| should have a '-' on top of the 'U' (I don't know how to do it on the keyboard) and..

Length of vector
|U| = Sqr(X^2 + Y^2 +.....+ n^2)

Which is positive anyway (unless you're going complex) so...

|U| * |V| >= 0

Farabi · February 24, 2012, 10:46:15 AM

Hi, THanks All, its right, it was for vector length.

THey said to find an angles between 2 vectors I need to calculate it this way Cos^-1(Ux.Vx+Uy.Vy+Uz.Vz)/|U| |V|. I dont get what is the logic behind it, but I hope it will just worked.

vanjast · February 24, 2012, 05:59:28 PM

Are you trying to work out the luminance or reflection off a surface in Dx... This is known as the Vector Dot Product

Farabi · February 25, 2012, 01:28:52 AM

Quote from: vanjast on February 24, 2012, 05:59:28 PM
Are you trying to work out the luminance or reflection off a surface in Dx... This is known as the Vector Dot Product

No, Im just wanted to know how to obtain an angle between 2 Vectors. I tried this but it did not worked

Code Select


FPGetAngles proc uses esi edi lpPos:dword,lpRotation:dword
	LOCAL signX,signY:dword
	LOCAL rslt:VERTEX
	LOCAL q:dword
	LOCAL t:qword
	;++ = 0-90
	;+- = 91-180
	;-- = 181=270
	;-+ = 271-360
	
	mov esi,lpPos
	mov edi,lpRotation
	; X = Y,Z
	; Y = X,Z
	; Z = X,Y
	invoke Vec_Normalize,addr rslt,lpPos
;	invoke Vec_Copy,addr rslt,lpPos

	fld rslt.y
	invoke FpuArcsin,0,0,129
	fstp [edi].VERTEX.x
	
	fld rslt.x
	fld rslt.z
	fpatan
	fstp q
	invoke Vec_RadToDeg,q
	fstp [edi].VERTEX.y
	
;	fld rslt.x
;	fld rslt.y
;	fpatan
;	fstp q
;	invoke Vec_RadToDeg,q
;	fldz
;	fstp [edi].VERTEX.z
	
	
	ret
FPGetAngles endp

On a few test it worked, like when you input X=10 but Y=Z=0, it will yield a right results. But problem occurs when you move the cameras. I dont know where went wrong, is it because the physic engine messed up the rotation order or what. But if that test was worked, it should be worked everywhere, but nevermind it, I given up. My brain almost exploded. :toothy

qWord · February 25, 2012, 02:35:09 AM

Code Select

VERTEX struct
    x   REAL8 ?
    y   REAL8 ?
    z   REAL8 ? 
VERTEX ends

Angle proc uses esi edi pAngle: ptr REAL4,pU:ptr VERTEX,pV:ptr VERTEX
LOCAL abs1:REAL8
LOCAL abs2:REAL8
    
    mov esi,pU
    mov edi,pV
    
    ;|U|
    fld [esi].VERTEX.x
    fmul st,st
    fld [esi].VERTEX.y
    fmul st,st
    faddp st(1),st
    fld [esi].VERTEX.z
    fmul st,st
    faddp st(1),st
    fsqrt
    fstp abs1
    .if !DWORD ptr abs1[0] && !DWORD ptr abs1[4]
        ; error: null vector
        xor eax,eax
        ret
    .endif

    ;|V|
    fld [edi].VERTEX.x
    fmul st,st
    fld [edi].VERTEX.y
    fmul st,st
    faddp st(1),st
    fld [edi].VERTEX.z
    fmul st,st
    faddp st(1),st
    fsqrt
    fst abs2
    .if !DWORD ptr abs2[0] && !DWORD ptr abs2[4]
        ; error: null vector
        xor eax,eax
        ret
    .endif
    
    ; |U|*|V|
    fmul abs1
    
    ; U*V
    fld [esi].VERTEX.x
    fmul [edi].VERTEX.x
    fld [esi].VERTEX.y
    fmul [edi].VERTEX.y
    faddp st(1),st
    fld [esi].VERTEX.z
    fmul [edi].VERTEX.z
    faddp st(1),st
    
    ; U*V / |U|*|V|
    fdivrp st(1),st
    
    ; acos(U*V / |U|*|V|)
    fst abs1
    test DWORD ptr abs1+4,80000000h
    fmul st,st
    fld st      
    fld1
    fsubrp st(1),st
    fdivp st(1),st
    fabs
    fsqrt
    fld1
    fpatan
    fld FP4(1.5707963267949) ; pi/2
    .if ZERO?
        fsubrp st(1),st 
    .else   
        faddp st(1),st
    .endif

    ; rad -> deg
    fmul FP4(57.2957795131) ; 180/pi
    
    mov edi,pAngle
    fstp REAL4 ptr [edi]
    
    mov eax,1
    ret
    
Angle endp

Farabi · February 25, 2012, 06:39:46 AM

Quote from: qWord on February 25, 2012, 02:35:09 AM
Code Select Expand
VERTEX struct x REAL8 ? y REAL8 ? z REAL8 ? VERTEX ends Angle proc uses esi edi pAngle: ptr REAL4,pU:ptr VERTEX,pV:ptr VERTEX LOCAL abs1:REAL8 LOCAL abs2:REAL8 mov esi,pU mov edi,pV ;|U| fld [esi].VERTEX.x fmul st,st fld [esi].VERTEX.y fmul st,st faddp st(1),st fld [esi].VERTEX.z fmul st,st faddp st(1),st fsqrt fstp abs1 .if !DWORD ptr abs1[0] && !DWORD ptr abs1[4] ; error: null vector xor eax,eax ret .endif ;|V| fld [edi].VERTEX.x fmul st,st fld [edi].VERTEX.y fmul st,st faddp st(1),st fld [edi].VERTEX.z fmul st,st faddp st(1),st fsqrt fst abs2 .if !DWORD ptr abs2[0] && !DWORD ptr abs2[4] ; error: null vector xor eax,eax ret .endif ; |U|*|V| fmul abs1 ; U*V fld [esi].VERTEX.x fmul [edi].VERTEX.x fld [esi].VERTEX.y fmul [edi].VERTEX.y faddp st(1),st fld [esi].VERTEX.z fmul [edi].VERTEX.z faddp st(1),st ; U*V / |U|*|V| fdivrp st(1),st ; acos(U*V / |U|*|V|) fst abs1 test DWORD ptr abs1+4,80000000h fmul st,st fld st fld1 fsubrp st(1),st fdivp st(1),st fabs fsqrt fld1 fpatan fld FP4(1.5707963267949) ; pi/2 .if ZERO? fsubrp st(1),st .else faddp st(1),st .endif ; rad -> deg fmul FP4(57.2957795131) ; 180/pi mov edi,pAngle fstp REAL4 ptr [edi] mov eax,1 ret Angle endp

Look cool. If I know how to use this and it worked, it mean youre a genius. I've bee looking for the logic behind this.

dedndave · February 25, 2012, 08:10:01 AM

Code Select

; acos(U*V / |U|*|V|)

although, it might be simplified...

http://steve.hollasch.net/cgindex/math/anglevec.html

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What is“|” mean?