boundingintervalhierarchy.java

Sunflow是一个照片级的渲染系统

package org.sunflow.core.accel;

import org.sunflow.core.AccelerationStructure;
import org.sunflow.core.IntersectionState;
import org.sunflow.core.PrimitiveList;
import org.sunflow.core.Ray;
import org.sunflow.math.BoundingBox;
import org.sunflow.system.Memory;
import org.sunflow.system.Timer;
import org.sunflow.system.UI;
import org.sunflow.system.UI.Module;
import org.sunflow.util.IntArray;

public class BoundingIntervalHierarchy implements AccelerationStructure {
    private int[] tree;
    private int[] objects;
    private PrimitiveList primitives;
    private BoundingBox bounds;
    private int maxPrims;

    public BoundingIntervalHierarchy() {
        maxPrims = 2;
    }

    public void build(PrimitiveList primitives) {
        this.primitives = primitives;
        int n = primitives.getNumPrimitives();
        UI.printDetailed(Module.ACCEL, "Getting bounding box ...");
        bounds = primitives.getWorldBounds(null);
        objects = new int[n];
        for (int i = 0; i < n; i++)
            objects[i] = i;
        UI.printDetailed(Module.ACCEL, "Creating tree ...");
        int initialSize = 3 * (2 * 6 * n + 1);
        IntArray tempTree = new IntArray((initialSize + 3) / 4);
        BuildStats stats = new BuildStats();
        Timer t = new Timer();
        t.start();
        buildHierarchy(tempTree, objects, stats);
        t.end();
        UI.printDetailed(Module.ACCEL, "Trimming tree ...");
        tree = tempTree.trim();
        // display stats
        stats.printStats();
        UI.printDetailed(Module.ACCEL, "  * Creation time:  %s", t);
        UI.printDetailed(Module.ACCEL, "  * Usage of init:  %3d%%", 100 * tree.length / initialSize);
        UI.printDetailed(Module.ACCEL, "  * Tree memory:    %s", Memory.sizeof(tree));
        UI.printDetailed(Module.ACCEL, "  * Indices memory: %s", Memory.sizeof(objects));
    }

    private static class BuildStats {
        private int numNodes;
        private int numLeaves;
        private int sumObjects;
        private int minObjects;
        private int maxObjects;
        private int sumDepth;
        private int minDepth;
        private int maxDepth;
        private int numLeaves0;
        private int numLeaves1;
        private int numLeaves2;
        private int numLeaves3;
        private int numLeaves4;
        private int numLeaves4p;
        private int numBVH2;

        BuildStats() {
            numNodes = numLeaves = 0;
            sumObjects = 0;
            minObjects = Integer.MAX_VALUE;
            maxObjects = Integer.MIN_VALUE;
            sumDepth = 0;
            minDepth = Integer.MAX_VALUE;
            maxDepth = Integer.MIN_VALUE;
            numLeaves0 = 0;
            numLeaves1 = 0;
            numLeaves2 = 0;
            numLeaves3 = 0;
            numLeaves4 = 0;
            numLeaves4p = 0;
            numBVH2 = 0;
        }

        void updateInner() {
            numNodes++;
        }

        void updateBVH2() {
            numBVH2++;
        }

        void updateLeaf(int depth, int n) {
            numLeaves++;
            minDepth = Math.min(depth, minDepth);
            maxDepth = Math.max(depth, maxDepth);
            sumDepth += depth;
            minObjects = Math.min(n, minObjects);
            maxObjects = Math.max(n, maxObjects);
            sumObjects += n;
            switch (n) {
                case 0:
                    numLeaves0++;
                    break;
                case 1:
                    numLeaves1++;
                    break;
                case 2:
                    numLeaves2++;
                    break;
                case 3:
                    numLeaves3++;
                    break;
                case 4:
                    numLeaves4++;
                    break;
                default:
                    numLeaves4p++;
                    break;
            }
        }

        void printStats() {
            UI.printDetailed(Module.ACCEL, "Tree stats:");
            UI.printDetailed(Module.ACCEL, "  * Nodes:          %d", numNodes);
            UI.printDetailed(Module.ACCEL, "  * Leaves:         %d", numLeaves);
            UI.printDetailed(Module.ACCEL, "  * Objects: min    %d", minObjects);
            UI.printDetailed(Module.ACCEL, "             avg    %.2f", (float) sumObjects / numLeaves);
            UI.printDetailed(Module.ACCEL, "           avg(n>0) %.2f", (float) sumObjects / (numLeaves - numLeaves0));
            UI.printDetailed(Module.ACCEL, "             max    %d", maxObjects);
            UI.printDetailed(Module.ACCEL, "  * Depth:   min    %d", minDepth);
            UI.printDetailed(Module.ACCEL, "             avg    %.2f", (float) sumDepth / numLeaves);
            UI.printDetailed(Module.ACCEL, "             max    %d", maxDepth);
            UI.printDetailed(Module.ACCEL, "  * Leaves w/: N=0  %3d%%", 100 * numLeaves0 / numLeaves);
            UI.printDetailed(Module.ACCEL, "               N=1  %3d%%", 100 * numLeaves1 / numLeaves);
            UI.printDetailed(Module.ACCEL, "               N=2  %3d%%", 100 * numLeaves2 / numLeaves);
            UI.printDetailed(Module.ACCEL, "               N=3  %3d%%", 100 * numLeaves3 / numLeaves);
            UI.printDetailed(Module.ACCEL, "               N=4  %3d%%", 100 * numLeaves4 / numLeaves);
            UI.printDetailed(Module.ACCEL, "               N>4  %3d%%", 100 * numLeaves4p / numLeaves);
            UI.printDetailed(Module.ACCEL, "  * BVH2 nodes:     %d (%3d%%)", numBVH2, 100 * numBVH2 / (numNodes + numLeaves - 2 * numBVH2));
        }
    }

    private void buildHierarchy(IntArray tempTree, int[] indices, BuildStats stats) {
        // create space for the first node
        tempTree.add(3 << 30); // dummy leaf
        tempTree.add(0);
        tempTree.add(0);
        if (objects.length == 0)
            return;
        // seed bbox
        float[] gridBox = { bounds.getMinimum().x, bounds.getMaximum().x,
                bounds.getMinimum().y, bounds.getMaximum().y,
                bounds.getMinimum().z, bounds.getMaximum().z };
        float[] nodeBox = { bounds.getMinimum().x, bounds.getMaximum().x,
                bounds.getMinimum().y, bounds.getMaximum().y,
                bounds.getMinimum().z, bounds.getMaximum().z };
        // seed subdivide function
        subdivide(0, objects.length - 1, tempTree, indices, gridBox, nodeBox, 0, 1, stats);
    }

    private void createNode(IntArray tempTree, int nodeIndex, int left, int right) {
        // write leaf node
        tempTree.set(nodeIndex + 0, (3 << 30) | left);
        tempTree.set(nodeIndex + 1, right - left + 1);
    }

    private void subdivide(int left, int right, IntArray tempTree, int[] indices, float[] gridBox, float[] nodeBox, int nodeIndex, int depth, BuildStats stats) {
        if ((right - left + 1) <= maxPrims || depth >= 64) {
            // write leaf node
            stats.updateLeaf(depth, right - left + 1);
            createNode(tempTree, nodeIndex, left, right);
            return;
        }
        // calculate extents
        int axis = -1, prevAxis, rightOrig;
        float clipL = Float.NaN, clipR = Float.NaN, prevClip = Float.NaN;
        float split = Float.NaN, prevSplit;
        boolean wasLeft = true;
        while (true) {
            prevAxis = axis;
            prevSplit = split;
            // perform quick consistency checks
            float d[] = { gridBox[1] - gridBox[0], gridBox[3] - gridBox[2],
                    gridBox[5] - gridBox[4] };
            if (d[0] < 0 || d[1] < 0 || d[2] < 0)
                throw new IllegalStateException("negative node extents");
            for (int i = 0; i < 3; i++) {
                if (nodeBox[2 * i + 1] < gridBox[2 * i] || nodeBox[2 * i] > gridBox[2 * i + 1]) {
                    UI.printError(Module.ACCEL, "Reached tree area in error - discarding node with: %d objects", right - left + 1);
                    throw new IllegalStateException("invalid node overlap");
                }
            }
            // find longest axis
            if (d[0] > d[1] && d[0] > d[2])
                axis = 0;
            else if (d[1] > d[2])
                axis = 1;
            else
                axis = 2;
            split = 0.5f * (gridBox[2 * axis] + gridBox[2 * axis + 1]);
            // partition L/R subsets
            clipL = Float.NEGATIVE_INFINITY;
            clipR = Float.POSITIVE_INFINITY;
            rightOrig = right; // save this for later
            float nodeL = Float.POSITIVE_INFINITY;
            float nodeR = Float.NEGATIVE_INFINITY;
            for (int i = left; i <= right;) {
                int obj = indices[i];
                float minb = primitives.getPrimitiveBound(obj, 2 * axis + 0);
                float maxb = primitives.getPrimitiveBound(obj, 2 * axis + 1);
                float center = (minb + maxb) * 0.5f;
                if (center <= split) {
                    // stay left
                    i++;
                    if (clipL < maxb)
                        clipL = maxb;
                } else {
                    // move to the right most
                    int t = indices[i];
                    indices[i] = indices[right];
                    indices[right] = t;
                    right--;
                    if (clipR > minb)
                        clipR = minb;
                }
                if (nodeL > minb)
                    nodeL = minb;
                if (nodeR < maxb)
                    nodeR = maxb;
            }
            // check for empty space
            if (nodeL > nodeBox[2 * axis + 0] && nodeR < nodeBox[2 * axis + 1]) {
                float nodeBoxW = nodeBox[2 * axis + 1] - nodeBox[2 * axis + 0];
                float nodeNewW = nodeR - nodeL;
                // node box is too big compare to space occupied by primitives?
                if (1.3f * nodeNewW < nodeBoxW) {
                    stats.updateBVH2();
                    int nextIndex = tempTree.getSize();
                    // allocate child
                    tempTree.add(0);
                    tempTree.add(0);
                    tempTree.add(0);
                    // write bvh2 clip node
                    stats.updateInner();
                    tempTree.set(nodeIndex + 0, (axis << 30) | (1 << 29) | nextIndex);
                    tempTree.set(nodeIndex + 1, Float.floatToRawIntBits(nodeL));
                    tempTree.set(nodeIndex + 2, Float.floatToRawIntBits(nodeR));
                    // update nodebox and recurse
                    nodeBox[2 * axis + 0] = nodeL;
                    nodeBox[2 * axis + 1] = nodeR;
                    subdivide(left, rightOrig, tempTree, indices, gridBox, nodeBox, nextIndex, depth + 1, stats);
                    return;
                }
            }
            // ensure we are making progress in the subdivision
            if (right == rightOrig) {
                // all left
                if (clipL <= split) {
                    // keep looping on left half
                    gridBox[2 * axis + 1] = split;
                    prevClip = clipL;
                    wasLeft = true;
                    continue;
                }
                if (prevAxis == axis && prevSplit == split) {
                    // we are stuck here - create a leaf
                    stats.updateLeaf(depth, right - left + 1);
                    createNode(tempTree, nodeIndex, left, right);
                    return;
                }
                gridBox[2 * axis + 1] = split;
                prevClip = Float.NaN;
            } else if (left > right) {
                // all right
                right = rightOrig;
                if (clipR >= split) {
                    // keep looping on right half
                    gridBox[2 * axis + 0] = split;
                    prevClip = clipR;
                    wasLeft = false;
                    continue;
                }
                if (prevAxis == axis && prevSplit == split) {
                    // we are stuck here - create a leaf
                    stats.updateLeaf(depth, right - left + 1);
                    createNode(tempTree, nodeIndex, left, right);
                    return;
                }
                gridBox[2 * axis + 0] = split;
                prevClip = Float.NaN;
            } else {
                // we are actually splitting stuff
                if (prevAxis != -1 && !Float.isNaN(prevClip)) {
                    // second time through - lets create the previous split
                    // since it produced empty space
                    int nextIndex = tempTree.getSize();
                    // allocate child node
                    tempTree.add(0);
                    tempTree.add(0);
                    tempTree.add(0);
                    if (wasLeft) {
                        // create a node with a left child
                        // write leaf node
                        stats.updateInner();
                        tempTree.set(nodeIndex + 0, (prevAxis << 30) | nextIndex);
                        tempTree.set(nodeIndex + 1, Float.floatToRawIntBits(prevClip));