Mathematical Topics from 3D Graphics - 3D Math Primer for Graphics and Game Development - page 461

/ / U n a t t e n u a t e d omni l i g h t c o l o r

uniform f l o a t 3 o m n i C o l o r ;

/ / View p o s i t i o n , i n MODEL space

uniform f l o a t 3 v i e w P o s ;

/ / C o n s t a n t ambient l i g h t c o l o r

uniform f l o a t 3 a m b i e n t L i g h t C o l o r ;

/ / M a t e r i a l g l o s s i n e s s ( phong exponent )

uniform f l o a t s p e c E x p o n e n t ;

/ / D i f f u s e and s p e c u l a r map s a m p l e r s . Note we assume t h a t d i f f u s e

/ / and spec maps use t h e same UV c o o r d s

sampler2D d i f f u s e M a p ;

sampler2D s p e c u l a r M a p ;

/ / P i x e l s h a d e r body

f l o a t 4 main ( I n p u t i n p u t ) : COLOR {

/ / F e t c h t h e t e x e l s t o g e t t h e m a t e r i a l c o l o r s

f l o a t 4 m a t D i f f = tex2D ( d i f f u s e M a p , i n p u t . uv ) ;

f l o a t 4 matSpec = tex2D ( s p e c u l a r M a p , i n p u t . uv ) ;

/ / Normalize i n t e r p o l a t e d v e r t e x normal

f l o a t 3 N = n o r m a l i z e ( i n p u t . n o r m a l ) ;

/ / Compute v e c t o r t o l i g h t

f l o a t 3 L = omniPos − i n p u t . modelPos ;

/ / Normalize i t , and s a v e o f f d i s t a n c e t o use l a t e r

/ / f o r a t t e n u a t i o n

f l o a t d i s t = l e n g t h ( L ) ;

L / = d i s t ;

/ / Compute view v e c t o r and h a l f w a y v e c t o r

f l o a t 3 V = n o r m a l i z e ( v i e w P o s − i n p u t . modelPos ) ;

f l o a t 3 H = n o r m a l i z e ( V + L ) ;

/ / Compute a t t e n u a t e d l i g h t c o l o r .

f l o a t 3 l i g h t C o l o r = o m n i C o l o r ∗ max ( 1 − d i s t ∗ invOmniRad , 0 ) ;

/ / Compute d i f f u s e and s p e c u l a r f a c t o r s

f l o a t d i f f F a c t o r = max ( dot ( N, L ) , 0 ) ;

f l o a t s p e c F a c t o r = pow ( max ( dot ( N,H ) , 0 ) , s p e c E x p o n e n t ) ;

/ / Compute e f f e c t i v e l i g h t c o l o r s

l i g h t C o l o r ∗ d i f f F a c t o r f l o a t 3 d i f f C o l o r = + a m b i e n t L i g h t C o l o r ;

l i g h t C o l o r ∗ s p e c F a c t o r ; f l o a t 3 s p e c C o l o r =

/ / Sum up c o l o r s . Note t h a t HLSL has a v e r y f l e x i b l e s w i z z l i n g s y s t e m

/ / which a l l o w s us t o a c c e s s a p o r t i o n o f a v e c t o r a s i f were a

/ / ”member” o f t h e v e c t o r

f l o a t 4 r e s u l t = m a t D i f f ; / / RGB and o p a c i t y from d i f f u s e map

r e s u l t . r g b ∗ = d i f f C o l o r ; / / modulate by d i f f u s e +ambient l i g h t i n g

r e s u l t . r g b += matSpec . r g b ∗ s p e c C o l o r ; / / add spec , i g n o r i n g map a l p h a

/ / Modulate i t by t h e c o n s t a n t and o u t p u t

r e t u r n r e s u l t ∗ c o n s t a n t C o l o r ;

}

Listing 10.14
Pixel shader for per-pixel lighting of a single omni plus ambient