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#ifndef lint |
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static const char RCSid[] = "$Id$"; |
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#endif |
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/* |
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================================================================== |
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Bias compensation for photon density estimates |
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(c) Fraunhofer Institute for Solar Energy Systems |
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================================================================== |
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$Id$ |
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*/ |
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void squeuePartition (PhotonSQNode* squeue, unsigned lo, |
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void squeuePartition (PhotonSearchQueueNode* squeue, unsigned lo, |
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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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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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unsigned l, h, p; |
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PhotonSQNode *lp, *hp, *pp; |
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float pivot, dist; |
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Photon* photon; |
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unsigned l, h, p; |
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PhotonSearchQueueNode *lp, *hp, *pp, tmp; |
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float pivot; |
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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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lp = squeue - lo + 1; |
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hp = squeue - hi + 1; |
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pp = squeue - p + 1; |
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pivot = pp -> dist; |
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pivot = pp -> dist2; |
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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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while (lp -> dist <= pivot && l <= h && l < hi) |
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while (lp -> dist2 <= pivot && l <= h && l < hi) |
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++l, --lp; |
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while (hp -> dist >= pivot && h >= l && h > lo) |
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while (hp -> dist2 >= pivot && h >= l && h > lo) |
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--h, ++hp; |
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if (l < h) { |
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/* Swap */ |
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photon = lp -> photon; |
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dist = lp -> dist; |
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lp -> photon = hp -> photon; |
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lp -> dist = hp -> dist; |
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hp -> photon = photon; |
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hp -> dist = dist; |
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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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} |
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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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Since lp -> dist > hp -> dist, we swap either l or p depending |
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Since lp -> dist2 > hp -> dist2, we swap either l or p depending |
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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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photon = hp -> photon; |
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dist = hp -> dist; |
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hp -> photon = pp -> photon; |
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hp -> dist = pivot; |
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pp -> photon = photon; |
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pp -> dist = dist; |
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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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if (h >= mid) |
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hi = h - 1; |
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if (h <= mid) |
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lo = h + 1; |
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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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unsigned i, numLo, numHi, numMid; |
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PhotonSQNode *sq; |
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PhotonBCNode *hist; |
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float r, totalWeight = 0; |
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PhotonSQNode *squeueEnd; |
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PhotonBCNode *histEnd; |
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COLOR fluxLo, fluxMid, irradVar, irradAvg, p, d; |
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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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if (!pmap -> biasCompHist) { |
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/* Allocate bias compensation history */ |
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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 = (PhotonBCNode*)malloc(i * sizeof(PhotonBCNode)); |
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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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if (!pmap -> biasCompHist) |
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error(USER, "can't allocate bias compensation history"); |
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} |
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numLo = min(pmap -> minGather, pmap -> squeueEnd - 1); |
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numHi = min(pmap -> maxGather, pmap -> squeueEnd - 1); |
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sq = squeueEnd = pmap -> squeue + pmap -> squeueEnd - 1; |
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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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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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squeuePartition(squeueEnd, 1, numLo + 1, numHi); |
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squeuePartition(sqEnd, 1, numLo + 1, numHi); |
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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. */ |
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for (i = 1; i <= numLo; i++, sq--) { |
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/* Make sure furthest two photons are consecutive wrt distance */ |
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squeuePartition(squeueEnd, i, i + 1, numLo + 1); |
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getPhotonFlux(sq -> photon, irrad); |
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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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addcolor(fluxLo, irrad); |
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/* Average radius between furthest two photons to improve accuracy */ |
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r = 0.25 * (sq -> dist + (sq - 1) -> dist + |
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2 * sqrt(sq -> dist * (sq - 1) -> dist)); |
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r = 0.25 * (sqn -> dist2 + (sqn - 1) -> dist2 + |
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2 * sqrt(sqn -> dist2 * (sqn - 1) -> dist2)); |
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/* 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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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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squeuePartition(squeueEnd, numLo, numMid, numHi); |
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squeuePartition(sqEnd, numLo, numMid, numHi); |
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/* Make sure furthest two photons are consecutive wrt distance */ |
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squeuePartition(squeueEnd, numMid, numMid + 1, numHi); |
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squeuePartition(sqEnd, numMid, numMid + 1, numHi); |
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copycolor(fluxMid, fluxLo); |
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sq = squeueEnd - numLo; |
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sqn = sqEnd - numLo; |
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/* Get irradiance for numMid photons (ignoring 1 / PI) */ |
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for (i = numLo; i < numMid; i++, sq--) { |
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getPhotonFlux(sq -> photon, irrad); |
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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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addcolor(fluxMid, irrad); |
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} |
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/* Average radius between furthest two photons to improve accuracy */ |
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r = 0.25 * (sq -> dist + (sq + 1) -> dist + |
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2 * sqrt(sq -> dist * (sq + 1) -> dist)); |
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r = 0.25 * (sqn -> dist2 + (sqn + 1) -> dist2 + |
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2 * sqrt(sqn -> dist2 * (sqn + 1) -> dist2)); |
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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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irradVar [i] = irradVar [i] / totalWeight - r * r; |
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} |
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/* Need more photons -- recurse on [numMid, numHi] */ |
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/* Need more photons --> recurse on [numMid, numHi] */ |
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numLo = numMid; |
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copycolor(fluxLo, fluxMid); |
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} |
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else |
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/* Deviation is probably bias -- need fewer photons, |
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/* Deviation is probably bias --> need fewer photons, |
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so recurse on [numLo, numMid] */ |
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numHi = numMid; |
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} |
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--histEnd; |
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for (i = 0; i <= 2; i++) { |
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/* Estimated relative error */ |
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d [i] = histEnd -> irrad [i] / irradAvg [i] - 1; |
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/* Update statistix */ |
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r = colorAvg(d); |
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pmap -> rmsError += r * r; |
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if (r < pmap -> minError) |
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pmap -> minError = r; |
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if (r > pmap -> maxError) |
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pmap -> maxError = r; |
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pmap -> rmsError += r * r; |
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if (numHi < pmap -> minGathered) |
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pmap -> minGathered = numHi; |
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if (numHi > pmap -> maxGathered) |
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pmap -> maxGathered = numHi; |
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/* Volume bias compensation disabled (probably redundant) */ |
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#if 0 |
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void volumeBiasComp (PhotonMap* pmap, const RAY* ray, COLOR irrad) |
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/* Photon volume density estimate with bias compensation -- czech dis |
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shit out! */ |
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pmap -> totalGathered += numMid; |
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++pmap -> numDensity; |
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} |
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#endif |
