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greg |
2.3 |
#ifndef lint |
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rschregle |
2.5 |
static const char RCSid[] = "$Id: pmapbias.c,v 4.7 2015/11/16 13:32:03 taschreg Exp taschreg $"; |
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greg |
2.3 |
#endif |
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rschregle |
2.5 |
|
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greg |
2.1 |
/* |
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================================================================== |
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Bias compensation for photon density estimates |
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For background see: |
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R. Schregle, "Bias Compensation for Photon Maps", |
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Computer Graphics Forum, v22:n4, pp. 729-742, Dec. 2003. |
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rschregle |
2.2 |
Roland Schregle ([email protected]) |
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(c) Fraunhofer Institute for Solar Energy Systems |
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greg |
2.1 |
================================================================== |
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rschregle |
2.5 |
$Id: pmapbias.c,v 4.7 2015/11/16 13:32:03 taschreg Exp taschreg $ |
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greg |
2.1 |
*/ |
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#include "pmapbias.h" |
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#include "pmap.h" |
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#include "pmaprand.h" |
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rschregle |
2.5 |
void squeuePartition (PhotonSearchQueueNode* squeue, unsigned lo, |
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greg |
2.1 |
unsigned mid, unsigned hi) |
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/* REVERSE Partition squeue such that all photons in |
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squeue-hi+1..squeue-mid are farther than the median at squeue-mid+1, |
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and those in squeue-mid+2..squeue-lo+1 are closer than the median. |
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This means that squeue points to the END of the queue, and the (1-based) |
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indices are offsets relative to it. This convoluted scheme is adopted |
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since the queue is initially a maxheap, so reverse sorting is expected |
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to be faster. */ |
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{ |
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rschregle |
2.5 |
unsigned l, h, p; |
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PhotonSearchQueueNode *lp, *hp, *pp, tmp; |
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float pivot; |
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greg |
2.1 |
|
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while (hi > lo) { |
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/* Grab pivot node in middle as an educated guess, since our |
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queue is sorta sorted. */ |
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l = lo; |
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h = hi; |
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p = mid; |
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lp = squeue - lo + 1; |
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hp = squeue - hi + 1; |
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pp = squeue - p + 1; |
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rschregle |
2.5 |
pivot = pp -> dist2; |
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greg |
2.1 |
|
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/* l & h converge, swapping elements out of order with respect to |
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pivot node. */ |
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while (l < h) { |
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rschregle |
2.5 |
while (lp -> dist2 <= pivot && l <= h && l < hi) |
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greg |
2.1 |
++l, --lp; |
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rschregle |
2.5 |
|
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while (hp -> dist2 >= pivot && h >= l && h > lo) |
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greg |
2.1 |
--h, ++hp; |
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if (l < h) { |
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/* Swap */ |
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rschregle |
2.5 |
tmp.idx = lp -> idx; |
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tmp.dist2 = lp -> dist2; |
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lp -> idx = hp -> idx; |
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lp -> dist2 = hp -> dist2; |
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hp -> idx = tmp.idx; |
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hp -> dist2 = tmp.dist2; |
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greg |
2.1 |
} |
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} |
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/* Swap convergence and pivot node */ |
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if (p > h) { |
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/* Need this otherwise shit happens! |
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rschregle |
2.5 |
Since lp -> dist2 > hp -> dist2, we swap either l or p depending |
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greg |
2.1 |
on whether we're above or below p */ |
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h = l; |
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hp = lp; |
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} |
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rschregle |
2.5 |
tmp.idx = hp -> idx; |
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tmp.dist2 = hp -> dist2; |
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hp -> idx = pp -> idx; |
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hp -> dist2 = pivot; |
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pp -> idx = tmp.idx; |
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pp -> dist2 = tmp.dist2; |
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greg |
2.1 |
if (h >= mid) |
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hi = h - 1; |
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rschregle |
2.5 |
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greg |
2.1 |
if (h <= mid) |
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lo = h + 1; |
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} |
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/* Once lo & hi have converged, we have found the median! */ |
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} |
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void biasComp (PhotonMap* pmap, COLOR irrad) |
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/* Photon density estimate with bias compensation -- czech dis shit out! */ |
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{ |
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rschregle |
2.5 |
unsigned i, numLo, numHi, numMid; |
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float r, totalWeight = 0; |
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COLOR fluxLo, fluxMid, irradVar, irradAvg, p, d; |
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Photon *photon; |
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PhotonSearchQueueNode *sqn, *sqEnd; |
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PhotonBiasCompNode *hist, *histEnd; |
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greg |
2.1 |
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if (!pmap -> biasCompHist) { |
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/* Allocate bias compensation history */ |
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rschregle |
2.5 |
numHi = pmap -> maxGather - pmap -> minGather; |
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for (i = pmap -> minGather + 1; numHi > 1; numHi >>= 1, ++i); |
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pmap -> biasCompHist = calloc(i, sizeof(PhotonBiasCompNode)); |
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greg |
2.1 |
if (!pmap -> biasCompHist) |
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error(USER, "can't allocate bias compensation history"); |
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} |
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rschregle |
2.5 |
numLo = min(pmap -> minGather, pmap -> squeue.tail - 1); |
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numHi = min(pmap -> maxGather, pmap -> squeue.tail - 1); |
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sqn = sqEnd = pmap -> squeue.node + pmap -> squeue.tail - 1; |
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greg |
2.1 |
histEnd = pmap -> biasCompHist; |
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setcolor(fluxLo, 0, 0, 0); |
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/* Partition to get numLo closest photons starting from END of queue */ |
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rschregle |
2.5 |
squeuePartition(sqEnd, 1, numLo + 1, numHi); |
129 |
greg |
2.1 |
|
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/* Get irradiance estimates (ignoring 1 / PI) using 1..numLo photons |
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and chuck in history. Queue is traversed BACKWARDS. */ |
132 |
rschregle |
2.5 |
for (i = 1; i <= numLo; i++, sqn--) { |
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/* Make sure furthest two photons are consecutive w.r.t. distance */ |
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squeuePartition(sqEnd, i, i + 1, numLo + 1); |
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photon = getNearestPhoton(&pmap -> squeue, sqn -> idx); |
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getPhotonFlux(photon, irrad); |
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greg |
2.1 |
addcolor(fluxLo, irrad); |
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/* Average radius between furthest two photons to improve accuracy */ |
139 |
rschregle |
2.5 |
r = 0.25 * (sqn -> dist2 + (sqn - 1) -> dist2 + |
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2 * sqrt(sqn -> dist2 * (sqn - 1) -> dist2)); |
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greg |
2.1 |
/* Add irradiance and weight to history. Weights should increase |
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monotonically based on number of photons used for the estimate. */ |
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histEnd -> irrad [0] = fluxLo [0] / r; |
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histEnd -> irrad [1] = fluxLo [1] / r; |
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histEnd -> irrad [2] = fluxLo [2] / r; |
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totalWeight += histEnd++ -> weight = BIASCOMP_WGT((float)i); |
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} |
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/* Compute expected value (average) and variance of irradiance based on |
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history for numLo photons. */ |
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setcolor(irradAvg, 0, 0, 0); |
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setcolor(irradVar, 0, 0, 0); |
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for (hist = pmap -> biasCompHist; hist < histEnd; ++hist) |
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for (i = 0; i <= 2; ++i) { |
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irradAvg [i] += r = hist -> weight * hist -> irrad [i]; |
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irradVar [i] += r * hist -> irrad [i]; |
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} |
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for (i = 0; i <= 2; ++i) { |
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r = irradAvg [i] /= totalWeight; |
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irradVar [i] = irradVar [i] / totalWeight - r * r; |
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} |
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/* Do binary search within interval [numLo, numHi]. numLo is towards |
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the END of the queue. */ |
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while (numHi - numLo > 1) { |
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numMid = (numLo + numHi) >> 1; |
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/* Split interval to get numMid closest photons starting from the |
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END of the queue */ |
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rschregle |
2.5 |
squeuePartition(sqEnd, numLo, numMid, numHi); |
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greg |
2.1 |
/* Make sure furthest two photons are consecutive wrt distance */ |
173 |
rschregle |
2.5 |
squeuePartition(sqEnd, numMid, numMid + 1, numHi); |
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greg |
2.1 |
copycolor(fluxMid, fluxLo); |
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rschregle |
2.5 |
sqn = sqEnd - numLo; |
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greg |
2.1 |
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/* Get irradiance for numMid photons (ignoring 1 / PI) */ |
178 |
rschregle |
2.5 |
for (i = numLo; i < numMid; i++, sqn--) { |
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photon = getNearestPhoton(&pmap -> squeue, sqn -> idx); |
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getPhotonFlux(photon, irrad); |
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greg |
2.1 |
addcolor(fluxMid, irrad); |
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} |
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/* Average radius between furthest two photons to improve accuracy */ |
185 |
rschregle |
2.5 |
r = 0.25 * (sqn -> dist2 + (sqn + 1) -> dist2 + |
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2 * sqrt(sqn -> dist2 * (sqn + 1) -> dist2)); |
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greg |
2.1 |
|
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/* Get deviation from current average, and probability that it's due |
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to noise from gaussian distribution based on current variance. Since |
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we are doing this for each colour channel we can also detect |
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chromatic bias. */ |
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for (i = 0; i <= 2; ++i) { |
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d [i] = irradAvg [i] - (irrad [i] = fluxMid [i] / r); |
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p [i] = exp(-0.5 * d [i] * d [i] / irradVar [i]); |
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} |
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if (pmapRandom(pmap -> randState) < colorAvg(p)) { |
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/* Deviation is probably noise, so add mid irradiance to history */ |
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copycolor(histEnd -> irrad, irrad); |
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totalWeight += histEnd++ -> weight = BIASCOMP_WGT((float)numMid); |
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setcolor(irradAvg, 0, 0, 0); |
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setcolor(irradVar, 0, 0, 0); |
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/* Update average and variance */ |
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for (hist = pmap -> biasCompHist; hist < histEnd; ++hist) |
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for (i = 0; i <= 2; i++) { |
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r = hist -> irrad [i]; |
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irradAvg [i] += hist -> weight * r; |
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irradVar [i] += hist -> weight * r * r; |
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} |
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for (i = 0; i <= 2; i++) { |
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r = irradAvg [i] /= totalWeight; |
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irradVar [i] = irradVar [i] / totalWeight - r * r; |
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} |
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217 |
rschregle |
2.5 |
/* Need more photons --> recurse on [numMid, numHi] */ |
218 |
greg |
2.1 |
numLo = numMid; |
219 |
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copycolor(fluxLo, fluxMid); |
220 |
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} |
221 |
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else |
222 |
rschregle |
2.5 |
/* Deviation is probably bias --> need fewer photons, |
223 |
greg |
2.1 |
so recurse on [numLo, numMid] */ |
224 |
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numHi = numMid; |
225 |
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} |
226 |
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227 |
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--histEnd; |
228 |
rschregle |
2.5 |
|
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greg |
2.1 |
for (i = 0; i <= 2; i++) { |
230 |
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/* Estimated relative error */ |
231 |
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d [i] = histEnd -> irrad [i] / irradAvg [i] - 1; |
232 |
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233 |
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#ifdef BIASCOMP_BWIDTH |
234 |
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/* Return bandwidth instead of irradiance */ |
235 |
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irrad [i] = numHi / PI; |
236 |
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#else |
237 |
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/* 1 / PI required as ambient normalisation factor */ |
238 |
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irrad [i] = histEnd -> irrad [i] / (PI * PI); |
239 |
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#endif |
240 |
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} |
241 |
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242 |
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/* Update statistix */ |
243 |
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r = colorAvg(d); |
244 |
rschregle |
2.5 |
pmap -> rmsError += r * r; |
245 |
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246 |
greg |
2.1 |
if (r < pmap -> minError) |
247 |
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pmap -> minError = r; |
248 |
rschregle |
2.5 |
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249 |
greg |
2.1 |
if (r > pmap -> maxError) |
250 |
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pmap -> maxError = r; |
251 |
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252 |
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if (numHi < pmap -> minGathered) |
253 |
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pmap -> minGathered = numHi; |
254 |
rschregle |
2.5 |
|
255 |
greg |
2.1 |
if (numHi > pmap -> maxGathered) |
256 |
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pmap -> maxGathered = numHi; |
257 |
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258 |
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pmap -> totalGathered += numHi; |
259 |
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++pmap -> numDensity; |
260 |
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} |
261 |
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262 |
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263 |
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264 |
rschregle |
2.5 |
/* Volume bias compensation disabled (probably redundant) */ |
265 |
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#if 0 |
266 |
greg |
2.1 |
void volumeBiasComp (PhotonMap* pmap, const RAY* ray, COLOR irrad) |
267 |
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/* Photon volume density estimate with bias compensation -- czech dis |
268 |
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shit out! */ |
269 |
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{ |
270 |
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unsigned i, numLo, numHi, numMid = 0; |
271 |
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PhotonSQNode *sq; |
272 |
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PhotonBCNode *hist; |
273 |
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const float gecc2 = ray -> gecc * ray -> gecc; |
274 |
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float r, totalWeight = 0; |
275 |
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PhotonSQNode *squeueEnd; |
276 |
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PhotonBCNode *histEnd; |
277 |
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COLOR fluxLo, fluxMid, irradVar, irradAvg, p, d; |
278 |
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279 |
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if (!pmap -> biasCompHist) { |
280 |
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/* Allocate bias compensation history */ |
281 |
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numHi = pmap -> maxGather - pmap -> minGather; |
282 |
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for (i = pmap -> minGather + 1; numHi > 1; numHi >>= 1, ++i); |
283 |
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pmap -> biasCompHist = (PhotonBCNode*)malloc(i * sizeof(PhotonBCNode)); |
284 |
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if (!pmap -> biasCompHist) |
285 |
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error(USER, "can't allocate bias compensation history"); |
286 |
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} |
287 |
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288 |
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numLo = min(pmap -> minGather, pmap -> squeueEnd - 1); |
289 |
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numHi = min(pmap -> maxGather, pmap -> squeueEnd - 1); |
290 |
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sq = squeueEnd = pmap -> squeue + pmap -> squeueEnd - 1; |
291 |
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histEnd = pmap -> biasCompHist; |
292 |
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setcolor(fluxLo, 0, 0, 0); |
293 |
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/* Partition to get numLo closest photons starting from END of queue */ |
294 |
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squeuePartition(squeueEnd, 1, numLo, numHi); |
295 |
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296 |
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/* Get irradiance estimates (ignoring constants) using 1..numLo photons |
297 |
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and chuck in history. Queue is traversed BACKWARDS. */ |
298 |
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for (i = 1; i <= numLo; i++, sq--) { |
299 |
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/* Make sure furthest two photons are consecutive wrt distance */ |
300 |
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squeuePartition(squeueEnd, i, i + 1, numHi); |
301 |
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302 |
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/* Compute phase function for inscattering from photon */ |
303 |
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if (gecc2 <= FTINY) |
304 |
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r = 1; |
305 |
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else { |
306 |
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r = DOT(ray -> rdir, sq -> photon -> norm) / 127; |
307 |
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r = 1 + gecc2 - 2 * ray -> gecc * r; |
308 |
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r = (1 - gecc2) / (r * sqrt(r)); |
309 |
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} |
310 |
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311 |
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getPhotonFlux(sq -> photon, irrad); |
312 |
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scalecolor(irrad, r); |
313 |
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addcolor(fluxLo, irrad); |
314 |
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/* Average radius between furthest two photons to improve accuracy */ |
315 |
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r = 0.25 * (sq -> dist + (sq - 1) -> dist + |
316 |
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2 * sqrt(sq -> dist * (sq - 1) -> dist)); |
317 |
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r *= sqrt(r); |
318 |
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/* Add irradiance and weight to history. Weights should increase |
319 |
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monotonically based on number of photons used for the estimate. */ |
320 |
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histEnd -> irrad [0] = fluxLo [0] / r; |
321 |
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histEnd -> irrad [1] = fluxLo [1] / r; |
322 |
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histEnd -> irrad [2] = fluxLo [2] / r; |
323 |
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totalWeight += histEnd++ -> weight = BIASCOMP_WGT((float)i); |
324 |
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} |
325 |
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326 |
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/* Compute expected value (average) and variance of irradiance based on |
327 |
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history for numLo photons. */ |
328 |
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setcolor(irradAvg, 0, 0, 0); |
329 |
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setcolor(irradVar, 0, 0, 0); |
330 |
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331 |
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for (hist = pmap -> biasCompHist; hist < histEnd; ++hist) |
332 |
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for (i = 0; i <= 2; ++i) { |
333 |
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irradAvg [i] += r = hist -> weight * hist -> irrad [i]; |
334 |
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irradVar [i] += r * hist -> irrad [i]; |
335 |
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} |
336 |
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337 |
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for (i = 0; i <= 2; ++i) { |
338 |
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r = irradAvg [i] /= totalWeight; |
339 |
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irradVar [i] = irradVar [i] / totalWeight - r * r; |
340 |
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} |
341 |
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|
342 |
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/* Do binary search within interval [numLo, numHi]. numLo is towards |
343 |
|
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the END of the queue. */ |
344 |
|
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while (numHi - numLo > 1) { |
345 |
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numMid = (numLo + numHi) >> 1; |
346 |
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/* Split interval to get numMid closest photons starting from the |
347 |
|
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END of the queue */ |
348 |
|
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squeuePartition(squeueEnd, numLo, numMid, numHi); |
349 |
|
|
/* Make sure furthest two photons are consecutive wrt distance */ |
350 |
|
|
squeuePartition(squeueEnd, numMid, numMid + 1, numHi); |
351 |
|
|
copycolor(fluxMid, fluxLo); |
352 |
|
|
sq = squeueEnd - numLo; |
353 |
|
|
|
354 |
|
|
/* Get irradiance for numMid photons (ignoring constants) */ |
355 |
|
|
for (i = numLo; i < numMid; i++, sq--) { |
356 |
|
|
/* Compute phase function for inscattering from photon */ |
357 |
|
|
if (gecc2 <= FTINY) |
358 |
|
|
r = 1; |
359 |
|
|
else { |
360 |
|
|
r = DOT(ray -> rdir, sq -> photon -> norm) / 127; |
361 |
|
|
r = 1 + gecc2 - 2 * ray -> gecc * r; |
362 |
|
|
r = (1 - gecc2) / (r * sqrt(r)); |
363 |
|
|
} |
364 |
|
|
|
365 |
|
|
getPhotonFlux(sq -> photon, irrad); |
366 |
|
|
scalecolor(irrad, r); |
367 |
|
|
addcolor(fluxMid, irrad); |
368 |
|
|
} |
369 |
|
|
|
370 |
|
|
/* Average radius between furthest two photons to improve accuracy */ |
371 |
|
|
r = 0.25 * (sq -> dist + (sq + 1) -> dist + |
372 |
|
|
2 * sqrt(sq -> dist * (sq + 1) -> dist)); |
373 |
|
|
r *= sqrt(r); |
374 |
|
|
|
375 |
|
|
/* Get deviation from current average, and probability that it's due |
376 |
|
|
to noise from gaussian distribution based on current variance. Since |
377 |
|
|
we are doing this for each colour channel we can also detect |
378 |
|
|
chromatic bias. */ |
379 |
|
|
for (i = 0; i <= 2; ++i) { |
380 |
|
|
d [i] = irradAvg [i] - (irrad [i] = fluxMid [i] / r); |
381 |
|
|
p [i] = exp(-0.5 * d [i] * d [i] / irradVar [i]); |
382 |
|
|
} |
383 |
|
|
|
384 |
|
|
if (pmapRandom(pmap -> randState) < colorAvg(p)) { |
385 |
|
|
/* Deviation is probably noise, so add mid irradiance to history */ |
386 |
|
|
copycolor(histEnd -> irrad, irrad); |
387 |
|
|
totalWeight += histEnd++ -> weight = BIASCOMP_WGT((float)numMid); |
388 |
|
|
setcolor(irradAvg, 0, 0, 0); |
389 |
|
|
setcolor(irradVar, 0, 0, 0); |
390 |
|
|
|
391 |
|
|
/* Update average and variance */ |
392 |
|
|
for (hist = pmap -> biasCompHist; hist < histEnd; ++hist) |
393 |
|
|
for (i = 0; i <= 2; i++) { |
394 |
|
|
r = hist -> irrad [i]; |
395 |
|
|
irradAvg [i] += hist -> weight * r; |
396 |
|
|
irradVar [i] += hist -> weight * r * r; |
397 |
|
|
} |
398 |
|
|
for (i = 0; i <= 2; i++) { |
399 |
|
|
r = irradAvg [i] /= totalWeight; |
400 |
|
|
irradVar [i] = irradVar [i] / totalWeight - r * r; |
401 |
|
|
} |
402 |
|
|
|
403 |
|
|
/* Need more photons -- recurse on [numMid, numHi] */ |
404 |
|
|
numLo = numMid; |
405 |
|
|
copycolor(fluxLo, fluxMid); |
406 |
|
|
} |
407 |
|
|
else |
408 |
|
|
/* Deviation is probably bias -- need fewer photons, |
409 |
|
|
so recurse on [numLo, numMid] */ |
410 |
|
|
numHi = numMid; |
411 |
|
|
} |
412 |
|
|
|
413 |
|
|
--histEnd; |
414 |
|
|
for (i = 0; i <= 2; i++) { |
415 |
|
|
/* Estimated relative error */ |
416 |
|
|
d [i] = histEnd -> irrad [i] / irradAvg [i] - 1; |
417 |
|
|
/* Divide by 4 / 3 * PI for search volume (r^3 already accounted |
418 |
|
|
for) and phase function normalization factor 1 / (4 * PI) */ |
419 |
|
|
irrad [i] = histEnd -> irrad [i] * 3 / (16 * PI * PI); |
420 |
|
|
} |
421 |
|
|
|
422 |
|
|
/* Update statistix */ |
423 |
|
|
r = colorAvg(d); |
424 |
|
|
if (r < pmap -> minError) |
425 |
|
|
pmap -> minError = r; |
426 |
|
|
if (r > pmap -> maxError) |
427 |
|
|
pmap -> maxError = r; |
428 |
|
|
pmap -> rmsError += r * r; |
429 |
|
|
|
430 |
|
|
if (numMid < pmap -> minGathered) |
431 |
|
|
pmap -> minGathered = numMid; |
432 |
|
|
if (numMid > pmap -> maxGathered) |
433 |
|
|
pmap -> maxGathered = numMid; |
434 |
|
|
|
435 |
|
|
pmap -> totalGathered += numMid; |
436 |
|
|
++pmap -> numDensity; |
437 |
|
|
} |
438 |
rschregle |
2.5 |
#endif |