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