Mathematical Topics from 3D Graphics - 3D Math Primer for Graphics and Game Development - page 473

/ / f o r t h e c u r r e n t pose . Note t h e m a t r i x m u l t i p l i c a t i o n

/ / [ 1 x3 ] = [ 1 x4 ] x [ 4 x3 ]

o u t p u t . modelPos = mul ( i n p u t . pos , b l e n d e d M a t ) ;

o u t p u t . n o r m a l = mul ( f l o a t 4 ( i n p u t . normal , 0 ) , b l e n d e d M a t ) ;

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

/ / T r a n s f o r m v e r t e x p o s i t i o n t o c l i p space .

o u t p u t . c l i p P o s = mul ( f l o a t 4 ( o u t p u t . modelPos , 1 ) , m o d e l T o C l i p ) ;

/ / P a s s t h r o u g h UVs

o u t p u t . uv = i n p u t . uv ;

r e t u r n o u t p u t ;

}

Listing 10.23
Vertex shader for skinned geometry

We have declared the vertices as an array of vertex shader constants, and
sending all these matrices to the hardware can be a significant performance
bottleneck. On certain platforms there are more e cient ways of doing this,
such as indexing into an auxiliary “vertex” stream.
Next, let's show how to use normal mapping on a skinned mesh. The
vertex shader in Listing 10.24 could be used with the pixel shader in List-
ing 10.22.

/ / Mesh i n p u t s .

s t r u c t I n p u t {

f l o a t 4 p o s : POSITION ; / / model space posn ( b i n d i n g pose )

f l o a t 3 n o r m a l : NORMAL ; / / v e r t e x normal i n model space

f l o a t 4 t a n g e n t D e t : TANGENT ; / / model space t a n g e n t , d e t i n w

by te 4 bones : BLENDINDICES ; / / Bone i n d i c e s . Unused e n t r i e s 0

f l o a t 4 w e i g h t : BLENDWEIGHT ; / / Blend w e i g h t s . Unused e n t r i e s 0

f l o a t 2 uv : TEXCOORD0 ; / / t e x t u r e c o o r d s f o r d i f f , spec maps

} ;

/ / V e r t e x s h a d e r o u t p u t

s t r u c t O u t p u t {

f l o a t 4 p o s : POSITION ; / / c l i p − space p o s i t i o n

f l o a t 2 uv : TEXCOORD0 ; / / t e x t u r e c o o r d s f o r a l l maps

f l o a t 3 L : TEXCOORD1 ; / / v e c t o r t o l i g h t , i n TANGENT space

f l o a t 3 H : TEXCOORD2 ; / / h a l f w a y v e c t o r , i n TANGENT space

f l o a t 3 l i g h t C o l o r : TEXCOORD3 ; / / l i g h t c o l o r + and a t t e n u a t i o n f a c t o r

} ;

/ / Model −> c l i p t r a n s f o r m m a t r i x .

uniform f l o a t 4 x 4 m o d e l T o C l i p ;

/ / A r r a y o f ' ' b i n d i n g pose −> c u r r e n t ' ' pose m a t r i c e s f o r each bone .

# d e f i n e MAX BONES 40

uniform f l o a t 4 x 3 b o n e M a t r i x [ MAX BONES ] ;

/ / Omni l i g h t p o s i t i o n , i n MODEL space , and r e c i p r o c a l o f

/ / f a l l o f f i n t h e w component

uniform f l o a t 4 omniPosAndInvRad ;

/ / 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 ;