/**
|
* Unpack an IEEE 754 single-precision float that is packed as a little-endian unsigned normalized vec4.
|
*
|
* @name czm_unpackFloat
|
* @glslFunction
|
*
|
* @param {vec4} packedFloat The packed float.
|
*
|
* @returns {float} The floating-point depth in arbitrary range.
|
*/
|
float czm_unpackFloat(vec4 packedFloat)
|
{
|
// Convert to [0.0, 255.0] and round to integer
|
packedFloat = floor(packedFloat * 255.0 + 0.5);
|
float sign = 1.0 - step(128.0, packedFloat[3]) * 2.0;
|
float exponent = 2.0 * mod(packedFloat[3], 128.0) + step(128.0, packedFloat[2]) - 127.0;
|
if (exponent == -127.0)
|
{
|
return 0.0;
|
}
|
float mantissa = mod(packedFloat[2], 128.0) * 65536.0 + packedFloat[1] * 256.0 + packedFloat[0] + float(0x800000);
|
float result = sign * exp2(exponent - 23.0) * mantissa;
|
return result;
|
}
|
