molstar
Version:
A comprehensive macromolecular library.
94 lines (87 loc) • 4.57 kB
JavaScript
"use strict";
/**
* Copyright (c) 2020 mol* contributors, licensed under MIT, See LICENSE file for more info.
*
* @author David Sehnal <david.sehnal@gmail.com>
*/
Object.defineProperty(exports, "__esModule", { value: true });
exports.rgba_to_float = void 0;
exports.rgba_to_float = `
// rgbaToFloat adapted from https://github.com/ihmeuw/glsl-rgba-to-float
// BSD 3-Clause License
//
// Copyright (c) 2019, Institute for Health Metrics and Evaluation All rights reserved.
// Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
// - Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
// - Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
// - Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
// INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
// IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
// OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
// OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
// OF THE POSSIBILITY OF SUCH DAMAGE.
ivec4 floatsToBytes(vec4 inputFloats, bool littleEndian) {
ivec4 bytes = ivec4(inputFloats * 255.0);
return (
littleEndian
? bytes.abgr
: bytes
);
}
// Break the four bytes down into an array of 32 bits.
void bytesToBits(const in ivec4 bytes, out bool bits[32]) {
for (int channelIndex = 0; channelIndex < 4; ++channelIndex) {
float acc = float(bytes[channelIndex]);
for (int indexInByte = 7; indexInByte >= 0; --indexInByte) {
float powerOfTwo = exp2(float(indexInByte));
bool bit = acc >= powerOfTwo;
bits[channelIndex * 8 + (7 - indexInByte)] = bit;
acc = mod(acc, powerOfTwo);
}
}
}
// Compute the exponent of the 32-bit float.
float getExponent(bool bits[32]) {
const int startIndex = 1;
const int bitStringLength = 8;
const int endBeforeIndex = startIndex + bitStringLength;
float acc = 0.0;
int pow2 = bitStringLength - 1;
for (int bitIndex = startIndex; bitIndex < endBeforeIndex; ++bitIndex) {
acc += float(bits[bitIndex]) * exp2(float(pow2--));
}
return acc;
}
// Compute the mantissa of the 32-bit float.
float getMantissa(bool bits[32], bool subnormal) {
const int startIndex = 9;
const int bitStringLength = 23;
const int endBeforeIndex = startIndex + bitStringLength;
// Leading/implicit/hidden bit convention:
// If the number is not subnormal (with exponent 0), we add a leading 1 digit.
float acc = float(!subnormal) * exp2(float(bitStringLength));
int pow2 = bitStringLength - 1;
for (int bitIndex = startIndex; bitIndex < endBeforeIndex; ++bitIndex) {
acc += float(bits[bitIndex]) * exp2(float(pow2--));
}
return acc;
}
// Parse the float from its 32 bits.
float bitsToFloat(bool bits[32]) {
float signBit = float(bits[0]) * -2.0 + 1.0;
float exponent = getExponent(bits);
bool subnormal = abs(exponent - 0.0) < 0.01;
float mantissa = getMantissa(bits, subnormal);
float exponentBias = 127.0;
return signBit * mantissa * exp2(exponent - exponentBias - 23.0);
}
float rgbaToFloat(vec4 texelRGBA, bool littleEndian) {
ivec4 rgbaBytes = floatsToBytes(texelRGBA, littleEndian);
bool bits[32];
bytesToBits(rgbaBytes, bits);
return bitsToFloat(bits);
}
`;