# ifndef COMMON_MAT_H
# define COMMON_MAT_H
typedef struct vec3 {
float v [ 3 ] ;
} vec3 ;
typedef struct vec4 {
float v [ 4 ] ;
} vec4 ;
typedef struct mat3 {
float v [ 3 * 3 ] ;
} mat3 ;
typedef struct mat4 {
float v [ 4 * 4 ] ;
} mat4 ;
static inline mat3 matmul3 ( const mat3 a , const mat3 b ) {
mat3 ret = { { 0.0 } } ;
for ( int r = 0 ; r < 3 ; r + + ) {
for ( int c = 0 ; c < 3 ; c + + ) {
float v = 0.0 ;
for ( int k = 0 ; k < 3 ; k + + ) {
v + = a . v [ r * 3 + k ] * b . v [ k * 3 + c ] ;
}
ret . v [ r * 3 + c ] = v ;
}
}
return ret ;
}
static inline vec3 matvecmul3 ( const mat3 a , const vec3 b ) {
vec3 ret = { { 0.0 } } ;
for ( int r = 0 ; r < 3 ; r + + ) {
for ( int c = 0 ; c < 3 ; c + + ) {
ret . v [ r ] + = a . v [ r * 3 + c ] * b . v [ c ] ;
}
}
return ret ;
}
static inline mat4 matmul ( const mat4 a , const mat4 b ) {
mat4 ret = { { 0.0 } } ;
for ( int r = 0 ; r < 4 ; r + + ) {
for ( int c = 0 ; c < 4 ; c + + ) {
float v = 0.0 ;
for ( int k = 0 ; k < 4 ; k + + ) {
v + = a . v [ r * 4 + k ] * b . v [ k * 4 + c ] ;
}
ret . v [ r * 4 + c ] = v ;
}
}
return ret ;
}
static inline vec4 matvecmul ( const mat4 a , const vec4 b ) {
vec4 ret = { { 0.0 } } ;
for ( int r = 0 ; r < 4 ; r + + ) {
for ( int c = 0 ; c < 4 ; c + + ) {
ret . v [ r ] + = a . v [ r * 4 + c ] * b . v [ c ] ;
}
}
return ret ;
}
// scales the input and output space of a transformation matrix
// that assumes pixel-center origin.
static inline mat3 transform_scale_buffer ( const mat3 in , float s ) {
// in_pt = ( transform(out_pt/s + 0.5) - 0.5) * s
mat3 transform_out = { {
1.0f / s , 0.0f , 0.5f ,
0.0f , 1.0f / s , 0.5f ,
0.0f , 0.0f , 1.0f ,
} } ;
mat3 transform_in = { {
s , 0.0f , - 0.5f * s ,
0.0f , s , - 0.5f * s ,
0.0f , 0.0f , 1.0f ,
} } ;
return matmul3 ( transform_in , matmul3 ( in , transform_out ) ) ;
}
# endif
