410 lines
12 KiB
C++
410 lines
12 KiB
C++
//
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//---------------------------------------------------------------------------
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// AABB-tree used for ray testing
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// Copyright(C) 2017 Magnus Norddahl
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// All rights reserved.
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with this program. If not, see http://www.gnu.org/licenses/
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//
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//--------------------------------------------------------------------------
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//
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#include "r_state.h"
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#include "g_levellocals.h"
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#include "hw_aabbtree.h"
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namespace hwrenderer
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{
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LevelAABBTree::LevelAABBTree(FLevelLocals *lev)
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{
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Level = lev;
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// Calculate the center of all lines
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TArray<FVector2> centroids;
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for (unsigned int i = 0; i < Level->lines.Size(); i++)
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{
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FVector2 v1 = { (float)Level->lines[i].v1->fX(), (float)Level->lines[i].v1->fY() };
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FVector2 v2 = { (float)Level->lines[i].v2->fX(), (float)Level->lines[i].v2->fY() };
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centroids.Push((v1 + v2) * 0.5f);
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}
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// Create the static subtree
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if (!GenerateTree(¢roids[0], false))
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return;
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int staticroot = nodes.Size() - 1;
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dynamicStartNode = nodes.Size();
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dynamicStartLine = treelines.Size();
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// Create the dynamic subtree
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if (GenerateTree(¢roids[0], true))
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{
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int dynamicroot = nodes.Size() - 1;
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// Create a shared root node
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FVector2 aabb_min, aabb_max;
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const auto &left = nodes[staticroot];
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const auto &right = nodes[dynamicroot];
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aabb_min.X = MIN(left.aabb_left, right.aabb_left);
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aabb_min.Y = MIN(left.aabb_top, right.aabb_top);
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aabb_max.X = MAX(left.aabb_right, right.aabb_right);
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aabb_max.Y = MAX(left.aabb_bottom, right.aabb_bottom);
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nodes.Push({ aabb_min, aabb_max, staticroot, dynamicroot });
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}
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// Add the lines referenced by the leaf nodes
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treelines.Resize(mapLines.Size());
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for (unsigned int i = 0; i < mapLines.Size(); i++)
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{
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const auto &line = Level->lines[mapLines[i]];
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auto &treeline = treelines[i];
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treeline.x = (float)line.v1->fX();
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treeline.y = (float)line.v1->fY();
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treeline.dx = (float)line.v2->fX() - treeline.x;
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treeline.dy = (float)line.v2->fY() - treeline.y;
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}
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}
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bool LevelAABBTree::GenerateTree(const FVector2 *centroids, bool dynamicsubtree)
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{
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// Create a list of level lines we want to add:
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TArray<int> line_elements;
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auto &maplines = Level->lines;
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for (unsigned int i = 0; i < maplines.Size(); i++)
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{
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if (!maplines[i].backsector)
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{
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bool isPolyLine = maplines[i].sidedef[0] && (maplines[i].sidedef[0]->Flags & WALLF_POLYOBJ);
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if (isPolyLine && dynamicsubtree)
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{
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line_elements.Push(mapLines.Size());
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mapLines.Push(i);
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}
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else if (!isPolyLine && !dynamicsubtree)
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{
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line_elements.Push(mapLines.Size());
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mapLines.Push(i);
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}
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}
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}
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if (line_elements.Size() == 0)
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return false;
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// GenerateTreeNode needs a buffer where it can store line indices temporarily when sorting lines into the left and right child AABB buckets
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TArray<int> work_buffer;
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work_buffer.Resize(line_elements.Size() * 2);
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// Generate the AABB tree
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GenerateTreeNode(&line_elements[0], (int)line_elements.Size(), centroids, &work_buffer[0]);
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return true;
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}
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bool LevelAABBTree::Update()
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{
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bool modified = false;
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for (unsigned int i = dynamicStartLine; i < mapLines.Size(); i++)
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{
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const auto &line = Level->lines[mapLines[i]];
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AABBTreeLine treeline;
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treeline.x = (float)line.v1->fX();
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treeline.y = (float)line.v1->fY();
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treeline.dx = (float)line.v2->fX() - treeline.x;
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treeline.dy = (float)line.v2->fY() - treeline.y;
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if (memcmp(&treelines[i], &treeline, sizeof(AABBTreeLine)))
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{
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TArray<int> path = FindNodePath(i, nodes.Size() - 1);
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if (path.Size())
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{
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float x1 = (float)line.v1->fX();
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float y1 = (float)line.v1->fY();
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float x2 = (float)line.v2->fX();
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float y2 = (float)line.v2->fY();
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int nodeIndex = path[0];
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nodes[nodeIndex].aabb_left = MIN(x1, x2);
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nodes[nodeIndex].aabb_right = MAX(x1, x2);
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nodes[nodeIndex].aabb_top = MIN(y1, y2);
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nodes[nodeIndex].aabb_bottom = MAX(y1, y2);
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for (unsigned int j = 1; j < path.Size(); j++)
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{
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auto &cur = nodes[path[j]];
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const auto &left = nodes[cur.left_node];
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const auto &right = nodes[cur.right_node];
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cur.aabb_left = MIN(left.aabb_left, right.aabb_left);
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cur.aabb_top = MIN(left.aabb_top, right.aabb_top);
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cur.aabb_right = MAX(left.aabb_right, right.aabb_right);
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cur.aabb_bottom = MAX(left.aabb_bottom, right.aabb_bottom);
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}
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treelines[i] = treeline;
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modified = true;
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}
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}
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}
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return modified;
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}
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TArray<int> LevelAABBTree::FindNodePath(unsigned int line, unsigned int node)
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{
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const AABBTreeNode &n = nodes[node];
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if (n.aabb_left > treelines[line].x || n.aabb_right < treelines[line].x ||
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n.aabb_top > treelines[line].y || n.aabb_bottom < treelines[line].y)
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{
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return {};
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}
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TArray<int> path;
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if (n.line_index == -1)
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{
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path = FindNodePath(line, n.left_node);
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if (path.Size() == 0)
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path = FindNodePath(line, n.right_node);
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if (path.Size())
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path.Push(node);
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}
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else if (n.line_index == (int)line)
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{
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path.Push(node);
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}
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return path;
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}
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double LevelAABBTree::RayTest(const DVector3 &ray_start, const DVector3 &ray_end)
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{
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// Precalculate some of the variables used by the ray/line intersection test
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DVector2 raydelta = ray_end - ray_start;
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double raydist2 = raydelta | raydelta;
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DVector2 raynormal = DVector2(raydelta.Y, -raydelta.X);
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double rayd = raynormal | ray_start;
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if (raydist2 < 1.0)
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return 1.0f;
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double hit_fraction = 1.0;
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// Walk the tree nodes
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int stack[32];
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int stack_pos = 1;
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stack[0] = nodes.Size() - 1; // root node is the last node in the list
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while (stack_pos > 0)
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{
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int node_index = stack[stack_pos - 1];
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if (!OverlapRayAABB(ray_start, ray_end, nodes[node_index]))
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{
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// If the ray doesn't overlap this node's AABB we're done for this subtree
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stack_pos--;
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}
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else if (nodes[node_index].line_index != -1) // isLeaf(node_index)
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{
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// We reached a leaf node. Do a ray/line intersection test to see if we hit the line.
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hit_fraction = MIN(IntersectRayLine(ray_start, ray_end, nodes[node_index].line_index, raydelta, rayd, raydist2), hit_fraction);
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stack_pos--;
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}
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else if (stack_pos == 32)
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{
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stack_pos--; // stack overflow - tree is too deep!
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}
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else
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{
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// The ray overlaps the node's AABB. Examine its child nodes.
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stack[stack_pos - 1] = nodes[node_index].left_node;
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stack[stack_pos] = nodes[node_index].right_node;
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stack_pos++;
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}
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}
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return hit_fraction;
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}
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bool LevelAABBTree::OverlapRayAABB(const DVector2 &ray_start2d, const DVector2 &ray_end2d, const AABBTreeNode &node)
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{
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// To do: simplify test to use a 2D test
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DVector3 ray_start = DVector3(ray_start2d, 0.0);
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DVector3 ray_end = DVector3(ray_end2d, 0.0);
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DVector3 aabb_min = DVector3(node.aabb_left, node.aabb_top, -1.0);
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DVector3 aabb_max = DVector3(node.aabb_right, node.aabb_bottom, 1.0);
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// Standard 3D ray/AABB overlapping test.
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// The details for the math here can be found in Real-Time Rendering, 3rd Edition.
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// We could use a 2D test here instead, which would probably simplify the math.
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DVector3 c = (ray_start + ray_end) * 0.5f;
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DVector3 w = ray_end - c;
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DVector3 h = (aabb_max - aabb_min) * 0.5f; // aabb.extents();
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c -= (aabb_max + aabb_min) * 0.5f; // aabb.center();
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DVector3 v = DVector3(fabs(w.X), fabs(w.Y), fabs(w.Z));
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if (fabs(c.X) > v.X + h.X || fabs(c.Y) > v.Y + h.Y || fabs(c.Z) > v.Z + h.Z)
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return false; // disjoint;
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if (fabs(c.Y * w.Z - c.Z * w.Y) > h.Y * v.Z + h.Z * v.Y ||
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fabs(c.X * w.Z - c.Z * w.X) > h.X * v.Z + h.Z * v.X ||
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fabs(c.X * w.Y - c.Y * w.X) > h.X * v.Y + h.Y * v.X)
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return false; // disjoint;
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return true; // overlap;
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}
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double LevelAABBTree::IntersectRayLine(const DVector2 &ray_start, const DVector2 &ray_end, int line_index, const DVector2 &raydelta, double rayd, double raydist2)
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{
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// Check if two line segments intersects (the ray and the line).
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// The math below does this by first finding the fractional hit for an infinitely long ray line.
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// If that hit is within the line segment (0 to 1 range) then it calculates the fractional hit for where the ray would hit.
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//
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// This algorithm is homemade - I would not be surprised if there's a much faster method out there.
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const double epsilon = 0.0000001;
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const AABBTreeLine &line = treelines[line_index];
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DVector2 raynormal = DVector2(raydelta.Y, -raydelta.X);
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DVector2 line_pos(line.x, line.y);
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DVector2 line_delta(line.dx, line.dy);
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double den = raynormal | line_delta;
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if (fabs(den) > epsilon)
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{
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double t_line = (rayd - (raynormal | line_pos)) / den;
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if (t_line >= 0.0 && t_line <= 1.0)
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{
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DVector2 linehitdelta = line_pos + line_delta * t_line - ray_start;
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double t = (raydelta | linehitdelta) / raydist2;
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return t > 0.0 ? t : 1.0;
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}
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}
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return 1.0;
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}
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int LevelAABBTree::GenerateTreeNode(int *lines, int num_lines, const FVector2 *centroids, int *work_buffer)
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{
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if (num_lines == 0)
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return -1;
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// Find bounding box and median of the lines
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FVector2 median = FVector2(0.0f, 0.0f);
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FVector2 aabb_min, aabb_max;
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auto &maplines = Level->lines;
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aabb_min.X = (float)maplines[mapLines[lines[0]]].v1->fX();
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aabb_min.Y = (float)maplines[mapLines[lines[0]]].v1->fY();
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aabb_max = aabb_min;
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for (int i = 0; i < num_lines; i++)
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{
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float x1 = (float)maplines[mapLines[lines[i]]].v1->fX();
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float y1 = (float)maplines[mapLines[lines[i]]].v1->fY();
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float x2 = (float)maplines[mapLines[lines[i]]].v2->fX();
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float y2 = (float)maplines[mapLines[lines[i]]].v2->fY();
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aabb_min.X = MIN(aabb_min.X, x1);
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aabb_min.X = MIN(aabb_min.X, x2);
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aabb_min.Y = MIN(aabb_min.Y, y1);
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aabb_min.Y = MIN(aabb_min.Y, y2);
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aabb_max.X = MAX(aabb_max.X, x1);
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aabb_max.X = MAX(aabb_max.X, x2);
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aabb_max.Y = MAX(aabb_max.Y, y1);
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aabb_max.Y = MAX(aabb_max.Y, y2);
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median += centroids[mapLines[lines[i]]];
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}
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median /= (float)num_lines;
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if (num_lines == 1) // Leaf node
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{
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nodes.Push(AABBTreeNode(aabb_min, aabb_max, lines[0]));
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return (int)nodes.Size() - 1;
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}
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// Find the longest axis
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float axis_lengths[2] =
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{
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aabb_max.X - aabb_min.X,
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aabb_max.Y - aabb_min.Y
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};
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int axis_order[2] = { 0, 1 };
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FVector2 axis_plane[2] = { FVector2(1.0f, 0.0f), FVector2(0.0f, 1.0f) };
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std::sort(axis_order, axis_order + 2, [&](int a, int b) { return axis_lengths[a] > axis_lengths[b]; });
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// Try sort at longest axis, then if that fails then the other one.
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// We place the sorted lines into work_buffer and then move the result back to the lines list when done.
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int left_count, right_count;
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for (int attempt = 0; attempt < 2; attempt++)
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{
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// Find the sort plane for axis
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FVector2 axis = axis_plane[axis_order[attempt]];
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FVector3 plane(axis, -(median | axis));
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// Sort lines into two based ib whether the line center is on the front or back side of a plane
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left_count = 0;
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right_count = 0;
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for (int i = 0; i < num_lines; i++)
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{
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int line_index = lines[i];
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float side = FVector3(centroids[mapLines[lines[i]]], 1.0f) | plane;
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if (side >= 0.0f)
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{
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work_buffer[left_count] = line_index;
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left_count++;
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}
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else
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{
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work_buffer[num_lines + right_count] = line_index;
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right_count++;
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}
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}
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if (left_count != 0 && right_count != 0)
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break;
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}
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// Check if something went wrong when sorting and do a random sort instead
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if (left_count == 0 || right_count == 0)
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{
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left_count = num_lines / 2;
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right_count = num_lines - left_count;
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}
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else
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{
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// Move result back into lines list:
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for (int i = 0; i < left_count; i++)
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lines[i] = work_buffer[i];
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for (int i = 0; i < right_count; i++)
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lines[i + left_count] = work_buffer[num_lines + i];
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}
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// Create child nodes:
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int left_index = -1;
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int right_index = -1;
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if (left_count > 0)
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left_index = GenerateTreeNode(lines, left_count, centroids, work_buffer);
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if (right_count > 0)
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right_index = GenerateTreeNode(lines + left_count, right_count, centroids, work_buffer);
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// Store resulting node and return its index
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nodes.Push(AABBTreeNode(aabb_min, aabb_max, left_index, right_index));
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return (int)nodes.Size() - 1;
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}
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}
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