将 3D 矢量浮点打包到无符号 int 中并将其解压缩

Packed 3D vector float points into unsigned int and unpacked it

本文关键字：int 无符号 解压缩 3D      更新时间：2023-10-16

GetPacked会将一个3D点打包成一个无符号的int。我想把它解压缩回原点，但不起作用。请帮忙

uint32_t GetPacked(float x, float y, float z)
{   
return ( 0xff000000 
| ( ( uint32_t ) ( ( x * 127.5f ) + 127.5f ) << 16 )
| ( ( uint32_t ) ( ( y * 127.5f ) + 127.5f ) << 8 ) 
| ( ( uint32_t ) ( ( z * 127.5f ) + 127.5f ) ) );
}

越野车开箱

void UnPacked(uint32_t p, float* _x, float* _y, float* _z)
{
*_z = ( ( p & 0xff ) - 127.5f) / 127.5f;
p >>= 8;
*_y = ( ( ( p ) & 0xff ) - 127.5f) / 127.5f;
p >>= 8;
*_x = ( ( ( p ) & 0xff ) - 127.5f) / 127.5f;
}

谢谢

PS：我在 ideone 中创建了一个在线测试

你会失去精度。

// a, b, b in the range of -127.5 +127.5
uint32_t Code(float a, float b, float c)
{
union
{
uint32_t u32;
uint8_t u8[4];
} u;
u.u8[3] = 0xff;
u.u8[0] = a + 127.5f;
u.u8[1] = b + 127.5f;
u.u8[2] = c + 127.5f;
return u.u32;
}
void DeCode(uint32_t u32, float *a, float *b, float *c)
{
union
{
uint32_t u32;
uint8_t u8[4];
} u;
u.u32 = u32;
*a = (float)u.u8[0] - 127.5f;
*b = (float)u.u8[1] - 127.5f;
*c = (float)u.u8[2] - 127.5f;
}

int main(void)
{
float a = 102.3f, b = -56.4f, c = -126f, d,e,f;
uint32_t coded = Code(a, b, c);
DeCode(coded, &d, &e, &f);
printf("Original values: %f,%f,%f. Coded -%x. Decoded %f,%f,%fn", a, b, c, coded, d, e, f);
}

为了获得更好的精度，您可以将其缩放到 10 位。

#define B10MAX      ((float)((1u << 10) - 1))
float Scale(float x)
{
return B10MAX * (x + 127.5f) / 255.0f;
}
float DeScale(unsigned x)
{
return 255.0f *(x) / B10MAX - 127.5f;
}
uint32_t Code10(float a, float b, float c)
{
union
{
uint32_t u32;
struct
{
uint32_t value1 : 10;
uint32_t value2 : 10;
uint32_t value3 : 10;
};
} u;
u.value1 = Scale(a);
u.value2 = Scale(b);
u.value3 = Scale(c);
return u.u32;
}
void DeCode10(uint32_t v, float *a, float *b, float *c)
{
union
{
uint32_t u32;
struct
{
uint32_t value1 : 10;
uint32_t value2 : 10;
uint32_t value3 : 10;
};
} u = {.u32 = v,};
*a = DeScale(u.value1);
*b = DeScale(u.value2);
*c = DeScale(u.value3);
}

在主要

coded = Code10(a, b, c);
DeCode10(coded, &d, &e, &f);
printf("Original values: %f,%f,%f. Coded = %x. Decoded %f,%f,%fn", a, b, c, coded, d, e, f);
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