Implementação de Stereo na Biblioteca VGL

Marcos Machado

Métodos de Stereo da Câmera do VGL

// Set parallax min and max (in degrees)

void SetParallax (float pmin, float pmax);

// Set screen

void SetPhysicalScreen (float w, float d);

// Set zero parallax setting (from 0.0 to 1.0)

void SetZeroParallax (float zps);

ComputeStereo do VGL: parâmetros

Parâmetros:pminpmaxwd

view volume

dw

xc

yc

zc

y'

x'

view frustumphysical screen

pminpmax

Controle do paralaxe

P/2

/2

d

P/2

/2

tg (/2 ) = P / 2d

Desktop: d = 60 cm, max = 1,5o Pmax 1,57 cm

Sala RV: d = 3 m, max = 1,5o Pmax 7,85 cm

ComputeStereo do VGL (1)

P/2 = d * tg (/2 )

float phy_pmin = - m_distance*(float)tan(m_pmin*VGL_PI/360.0f);

float phy_pmax = m_distance*(float)tan(m_pmax*VGL_PI/360.0f);

float pmin = phy_pmin/m_width*(m_vmax.x-m_vmin.x)*m_znear/m_vmin.z;

float pmax = phy_pmax/m_width*(m_vmax.x-m_vmin.x)*m_znear/m_vmin.z;

Escolhe Pmin e Pmax, calcula tc e ZZPS

tc/2 tc/2

Pmax/2

Pmin/2

Zfar

Zzps

Znear

Escolhe Pmin e Pmax, calcula tc e ZZPS

Pmin

tc

Znear

Zfar

ZZPS

Pmax

Escolhe Pmin e Pmax, calcula tc e ZZPS

tc

Znear

Zfar

ZZPS

Pmin Pmax

tc / Zfar = (Pmin + Pmax) / (Zfar - Znear)

tc = Zfar . (Pmin + Pmax) / (Zfar - Znear)

Escolhe Pmin e Pmax, calcula tc e ZZPS

tc

Znear

Zfar

ZZPS

Pmin Pmax

tc / ZZPS = Pmin / (ZZPS - Znear)

ZZPS = Znear . tc / (tc - Pmin)

tc = Zfar . (Pmin + Pmax) / (Zfar - Znear)

ComputeStereo do VGL (2)

tc = m_zfar*(pmin+pmax)/(m_zfar-m_znear);

zps = tc*m_znear/(tc-pmin);

Dados Pmin e ZZPS, calcula tc

tc/2 tc/2

Pmax/2

Pmin/2

Zfar

Zzps

Znear

zpsnearzps

mimc Z

ZZ

Pt

1

Dados Pmin e tc, calcula Pmax

tc/2 tc/2

Pmax/2

Pmin/2

Zfar

Zzps

Znear

mimcfar

nearfar PtZ

ZZP

max

ComputeStereo do VGL (3) if (m_zps>=0.0f) // if explicitly given

{ zps = m_znear + m_zps*(m_zfar-m_znear);

...

tc = (zps*pmin)/(zps-m_znear);

float p = tc*(m_zfar-m_znear)/m_zfar - pmin;

if (p > pmax)

{ // use pmax and find pmin

p = pmax / (zps/m_zfar*(m_zfar-m_znear)/(zps-m_znear) - 1.0f);

tc = (zps*p)/(zps-m_znear);

pmin = tc*(zps-m_znear)/zps; // pmin based on pmax value

} else

{

pmax = p; // pmax based on pmin value

} }

zpsnearzps

mimc Z

ZZ

Pt

1

farnearfar

c ZZZ

Pt

max

2

},min{21 ccc ttt

tc

HIT (Horizontal Image Translation)

HITHIT

Em OpenGL, projeção é feita no plano Znear

Znear

tc

Zzps

HIT (Horizontal Image Translation)

Znear

Zzps

Zfar

tc

HIT

HIT (Horizontal Image Translation)

Znear

Zzps

Zfar

tc

HIT

tc

HIT (Horizontal Image Translation)

Znear

Zzps

Zfar

tc

HIT = tc . Znear / Zzps

HIT

tc

ComputeStereo do VGL (4)

m_hit = m_tc * m_znear / zps * m_vmin.z / m_znear;

GetProjection( )

// compute stereo params

if (!m_updated)

ComputeStereo();

m.Identity();

m.Frustum(

m_vmin.x-m_curreye*m_hit, m_vmax.x-m_curreye*m_hit,

m_vmin.y,m_vmax.y,

m_vmin.z,m_vmax.z);

// current eye (-1=stereo left, 0=mono, 1=stereo right)

GetModelView( )

...

if (m_curreye != 0)

m.Translate(-m_curreye*m_tc,0.0f,0.0f);

...