200 lines
8.2 KiB
C++
200 lines
8.2 KiB
C++
//-*****************************************************************************
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// Copyright (C) Pixar. All rights reserved. *
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// *
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// This license governs use of the accompanying software. If you *
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// use the software, you accept this license. If you do not accept *
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// the license, do not use the software. *
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// *
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// 1. Definitions *
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// The terms "reproduce," "reproduction," "derivative works," and *
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// "distribution" have the same meaning here as under U.S. *
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// copyright law. A "contribution" is the original software, or *
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// any additions or changes to the software. *
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// A "contributor" is any person or entity that distributes its *
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// contribution under this license. *
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// "Licensed patents" are a contributor's patent claims that read *
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// directly on its contribution. *
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// *
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// 2. Grant of Rights *
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// (A) Copyright Grant- Subject to the terms of this license, *
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// including the license conditions and limitations in section 3, *
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// each contributor grants you a non-exclusive, worldwide, *
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// royalty-free copyright license to reproduce its contribution, *
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// prepare derivative works of its contribution, and distribute *
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// its contribution or any derivative works that you create. *
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// (B) Patent Grant- Subject to the terms of this license, *
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// including the license conditions and limitations in section 3, *
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// each contributor grants you a non-exclusive, worldwide, *
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// royalty-free license under its licensed patents to make, have *
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// made, use, sell, offer for sale, import, and/or otherwise *
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// dispose of its contribution in the software or derivative works *
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// of the contribution in the software. *
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// *
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// 3. Conditions and Limitations *
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// (A) No Trademark License- This license does not grant you *
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// rights to use any contributor's name, logo, or trademarks. *
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// (B) If you bring a patent claim against any contributor over *
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// patents that you claim are infringed by the software, your *
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// patent license from such contributor to the software ends *
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// automatically. *
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// (C) If you distribute any portion of the software, you must *
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// retain all copyright, patent, trademark, and attribution *
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// notices that are present in the software. *
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// (D) If you distribute any portion of the software in source *
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// code form, you may do so only under this license by including a *
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// complete copy of this license with your distribution. If you *
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// distribute any portion of the software in compiled or object *
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// code form, you may only do so under a license that complies *
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// with this license. *
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// (E) The software is licensed "as-is." You bear the risk of *
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// using it. The contributors give no express warranties, *
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// guarantees or conditions. You may have additional consumer *
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// rights under your local laws which this license cannot change. *
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// To the extent permitted under your local laws, the contributors *
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// exclude the implied warranties of merchantability, fitness for *
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// a particular purpose and non-infringement. *
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//-*****************************************************************************
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//-*****************************************************************************
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// Written by Pixar Animation Studios, 2011-2012.
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//-*****************************************************************************
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#include "PxDeepUtils.h"
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namespace PxDeep {
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//-*****************************************************************************
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// Density/Viz/DZ calculations are always performed in double precision.
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// We try to leave them alone as much as possible, but the logarithm can get
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// weird for very very small numbers. The "isfinite" call basically rules
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// out NaN and Infinity results, though it doesn't bother with subnormal
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// numbers, since the error case we're worried about is log being too big.
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// viz = exp( -dz * density )
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// log( viz ) = -dz * density
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// density = -log( viz ) / dz
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double DensityFromVizDz( double i_viz, double i_dz )
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{
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assert( i_viz >= 0.0 );
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assert( i_viz <= 1.0 );
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assert( i_dz >= 0.0 );
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if ( i_viz >= 1.0 )
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{
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// There's no attenuation at all, so there's no density!
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return 0.0;
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}
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else if ( i_viz <= 0.0 )
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{
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// There's total attenuation, so we use our max density.
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return PXDU_DENSITY_OF_VIZ_0;
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}
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else if ( i_dz <= 0.0 )
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{
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// There's no depth, and viz is greater than zero,
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// so we assume the density is as high as possible
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return PXDU_DENSITY_OF_VIZ_0;
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}
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else
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{
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double d = -log( i_viz ) / i_dz;
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if ( !isfinite( d ) )
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{
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return PXDU_DENSITY_OF_VIZ_0;
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}
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else
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{
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return d;
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}
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}
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}
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//-*****************************************************************************
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// We can often treat "density times dz" as a single quantity without
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// separating it.
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// viz = exp( -densityTimesDz )
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// log( viz ) = -densityTimesDz
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// densityTimesDz = -log( viz )
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double DensityTimesDzFromViz( double i_viz )
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{
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assert( i_viz >= 0.0 );
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assert( i_viz <= 1.0 );
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if ( i_viz >= 1.0 )
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{
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// There's no attenuation at all, so there's no density!
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return 0.0;
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}
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else if ( i_viz <= 0.0 )
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{
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// There's total attenuation, so we use our max density.
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return PXDU_DENSITY_OF_VIZ_0 * PXDU_DZ_OF_VIZ_0;
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}
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else
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{
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double d = -log( i_viz );
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if ( !isfinite( d ) )
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{
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return PXDU_DENSITY_OF_VIZ_0 * PXDU_DZ_OF_VIZ_0;
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}
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else
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{
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return d;
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}
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}
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}
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//-*****************************************************************************
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// viz = exp( -dz * density )
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// log( viz ) = -dz * density
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// dz = -log( viz ) / density
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// Note that this is basically the same as the computation above.
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double DzFromVizDensity( double i_viz, double i_density )
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{
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assert( i_viz >= 0.0 );
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assert( i_viz <= 1.0 );
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assert( i_density >= 0.0 );
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if ( i_viz >= 1.0 )
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{
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// There's no attenuation, so there's no depth.
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return 0.0;
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}
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else if ( i_viz <= 0.0 )
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{
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// There's total attenuation, so we use the smallest depth
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// for our max density.
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return PXDU_DZ_OF_VIZ_0;
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}
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else if ( i_density <= 0.0 )
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{
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// Hmmm. There's no density, but there is some attenuation,
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// which basically implies an infinite depth.
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// We'll use the minimum density.
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// This whole part is hacky at best.
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double dz = -log( i_viz ) / PXDU_MIN_NON_ZERO_DENSITY;
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if ( !isfinite( dz ) )
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{
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return PXDU_MAX_DZ;
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}
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else
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{
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return dz;
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}
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}
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else
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{
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double dz = -log( i_viz ) / i_density;
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if ( !isfinite( dz ) )
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{
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return PXDU_MAX_DZ;
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}
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else
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{
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return dz;
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}
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}
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}
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} // End namespace PxDeep
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