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@ -73,10 +73,6 @@ void btHeightfieldTerrainShape::initialize(
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m_useZigzagSubdivision = false;
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m_upAxis = upAxis;
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m_localScaling.setValue(btScalar(1.), btScalar(1.), btScalar(1.));
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m_vboundsGrid = NULL;
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m_vboundsChunkSize = 0;
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m_vboundsGridWidth = 0;
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m_vboundsGridLength = 0;
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// determine min/max axis-aligned bounding box (aabb) values
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switch (m_upAxis)
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@ -112,7 +108,6 @@ void btHeightfieldTerrainShape::initialize(
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btHeightfieldTerrainShape::~btHeightfieldTerrainShape()
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{
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clearAccelerator();
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}
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void btHeightfieldTerrainShape::getAabb(const btTransform& t, btVector3& aabbMin, btVector3& aabbMax) const
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@ -328,8 +323,6 @@ void btHeightfieldTerrainShape::processAllTriangles(btTriangleCallback* callback
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}
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}
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// TODO If m_vboundsGrid is available, use it to determine if we really need to process this area
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for (int j = startJ; j < endJ; j++)
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{
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for (int x = startX; x < endX; x++)
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@ -380,416 +373,3 @@ const btVector3& btHeightfieldTerrainShape::getLocalScaling() const
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{
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return m_localScaling;
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}
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struct GridRaycastState
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{
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int x; // Next quad coords
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int z;
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int prev_x; // Previous quad coords
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int prev_z;
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btScalar param; // Exit param for previous quad
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btScalar prevParam; // Enter param for previous quad
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btScalar maxDistanceFlat;
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btScalar maxDistance3d;
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};
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// TODO Does it really need to take 3D vectors?
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/// Iterates through a virtual 2D grid of unit-sized square cells,
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/// and executes an action on each cell intersecting the given segment, ordered from begin to end.
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/// Initially inspired by http://www.cse.yorku.ca/~amana/research/grid.pdf
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template <typename Action_T>
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void gridRaycast(Action_T &quadAction, const btVector3 &beginPos, const btVector3 &endPos)
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{
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GridRaycastState rs;
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rs.maxDistance3d = beginPos.distance(endPos);
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if (rs.maxDistance3d < 0.0001)
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// Consider the ray is too small to hit anything
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return;
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btScalar rayDirectionFlatX = endPos[0] - beginPos[0];
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btScalar rayDirectionFlatZ = endPos[2] - beginPos[2];
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rs.maxDistanceFlat = btSqrt(rayDirectionFlatX * rayDirectionFlatX + rayDirectionFlatZ * rayDirectionFlatZ);
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if(rs.maxDistanceFlat < 0.0001)
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{
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// Consider the ray vertical
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rayDirectionFlatX = 0;
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rayDirectionFlatZ = 0;
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}
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else
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{
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rayDirectionFlatX /= rs.maxDistanceFlat;
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rayDirectionFlatZ /= rs.maxDistanceFlat;
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}
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const int xiStep = rayDirectionFlatX > 0 ? 1 : rayDirectionFlatX < 0 ? -1 : 0;
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const int ziStep = rayDirectionFlatZ > 0 ? 1 : rayDirectionFlatZ < 0 ? -1 : 0;
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const float infinite = 9999999;
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const btScalar paramDeltaX = xiStep != 0 ? 1.f / btFabs(rayDirectionFlatX) : infinite;
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const btScalar paramDeltaZ = ziStep != 0 ? 1.f / btFabs(rayDirectionFlatZ) : infinite;
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// pos = param * dir
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btScalar paramCrossX; // At which value of `param` we will cross a x-axis lane?
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btScalar paramCrossZ; // At which value of `param` we will cross a z-axis lane?
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// paramCrossX and paramCrossZ are initialized as being the first cross
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// X initialization
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if (xiStep != 0)
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{
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if (xiStep == 1)
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paramCrossX = (ceil(beginPos[0]) - beginPos[0]) * paramDeltaX;
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else
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paramCrossX = (beginPos[0] - floor(beginPos[0])) * paramDeltaX;
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}
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else
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paramCrossX = infinite; // Will never cross on X
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// Z initialization
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if (ziStep != 0)
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{
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if (ziStep == 1)
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paramCrossZ = (ceil(beginPos[2]) - beginPos[2]) * paramDeltaZ;
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else
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paramCrossZ = (beginPos[2] - floor(beginPos[2])) * paramDeltaZ;
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}
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else
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paramCrossZ = infinite; // Will never cross on Z
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rs.x = static_cast<int>(floor(beginPos[0]));
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rs.z = static_cast<int>(floor(beginPos[2]));
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// Workaround cases where the ray starts at an integer position
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if (paramCrossX == 0.0)
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{
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paramCrossX += paramDeltaX;
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// If going backwards, we should ignore the position we would get by the above flooring,
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// because the ray is not heading in that direction
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if (xiStep == -1)
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rs.x -= 1;
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}
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if (paramCrossZ == 0.0)
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{
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paramCrossZ += paramDeltaZ;
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if (ziStep == -1)
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rs.z -= 1;
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}
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rs.prev_x = rs.x;
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rs.prev_z = rs.z;
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rs.param = 0;
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while (true)
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{
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rs.prev_x = rs.x;
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rs.prev_z = rs.z;
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rs.prevParam = rs.param;
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if (paramCrossX < paramCrossZ)
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{
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// X lane
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rs.x += xiStep;
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// Assign before advancing the param,
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// to be in sync with the initialization step
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rs.param = paramCrossX;
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paramCrossX += paramDeltaX;
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}
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else
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{
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// Z lane
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rs.z += ziStep;
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rs.param = paramCrossZ;
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paramCrossZ += paramDeltaZ;
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}
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if (rs.param > rs.maxDistanceFlat)
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{
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rs.param = rs.maxDistanceFlat;
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quadAction(rs);
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break;
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}
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else
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quadAction(rs);
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}
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}
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struct ProcessTrianglesAction
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{
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const btHeightfieldTerrainShape *shape;
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bool flipQuadEdges;
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bool useDiamondSubdivision;
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int width;
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int length;
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btTriangleCallback* callback;
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void exec(int x, int z) const
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{
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if(x < 0 || z < 0 || x >= width || z >= length)
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return;
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btVector3 vertices[3];
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// Check quad
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if (flipQuadEdges || (useDiamondSubdivision && (((z + x) & 1) > 0)))
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{
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// First triangle
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shape->getVertex(x, z, vertices[0]);
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shape->getVertex(x + 1, z, vertices[1]);
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shape->getVertex(x + 1, z + 1, vertices[2]);
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callback->processTriangle(vertices, x, z);
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// Second triangle
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shape->getVertex(x, z, vertices[0]);
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shape->getVertex(x + 1, z + 1, vertices[1]);
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shape->getVertex(x, z + 1, vertices[2]);
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callback->processTriangle(vertices, x, z);
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}
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else
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{
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// First triangle
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shape->getVertex(x, z, vertices[0]);
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shape->getVertex(x, z + 1, vertices[1]);
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shape->getVertex(x + 1, z, vertices[2]);
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callback->processTriangle(vertices, x, z);
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// Second triangle
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shape->getVertex(x + 1, z, vertices[0]);
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shape->getVertex(x, z + 1, vertices[1]);
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shape->getVertex(x + 1, z + 1, vertices[2]);
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callback->processTriangle(vertices, x, z);
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}
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}
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void operator ()(const GridRaycastState &bs) const
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{
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exec(bs.prev_x, bs.prev_z);
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}
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};
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struct ProcessVBoundsAction
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{
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const btHeightfieldTerrainShape::Range *vbounds;
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int width;
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int length;
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int chunkSize;
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btVector3 rayBegin;
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btVector3 rayEnd;
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btVector3 rayDir;
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ProcessTrianglesAction processTriangles;
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void operator ()(const GridRaycastState &rs) const
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{
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int x = rs.prev_x;
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int z = rs.prev_z;
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if(x < 0 || z < 0 || x >= width || z >= length)
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return;
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const btHeightfieldTerrainShape::Range chunk = vbounds[x + z * width];
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btVector3 enterPos;
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btVector3 exitPos;
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if (rs.maxDistanceFlat > 0.0001)
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{
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btScalar flatTo3d = chunkSize * rs.maxDistance3d / rs.maxDistanceFlat;
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btScalar enterParam3d = rs.prevParam * flatTo3d;
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btScalar exitParam3d = rs.param * flatTo3d;
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enterPos = rayBegin + rayDir * enterParam3d;
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exitPos = rayBegin + rayDir * exitParam3d;
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// We did enter the flat projection of the AABB,
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// but we have to check if we intersect it on the vertical axis
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if (enterPos[1] > chunk.max && exitPos[1] > chunk.max)
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return;
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if (enterPos[1] < chunk.min && exitPos[1] < chunk.min)
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return;
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}
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else
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{
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// Consider the ray vertical
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// (though we shouldn't reach this often because there is an early check up-front)
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enterPos = rayBegin;
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exitPos = rayEnd;
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}
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gridRaycast(processTriangles, enterPos, exitPos);
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// Note: it could be possible to have more than one grid at different levels,
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// to do this there would be a branch using a pointer to another ProcessVBoundsAction
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}
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};
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// TODO How do I interrupt the ray when there is a hit? `callback` does not return any result
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/// Performs a raycast using a hierarchical Bresenham algorithm.
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/// Does not allocate any memory by itself.
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void btHeightfieldTerrainShape::performRaycast(btTriangleCallback* callback, const btVector3& raySource, const btVector3& rayTarget) const
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{
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// Transform to cell-local
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btVector3 beginPos = raySource / m_localScaling;
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btVector3 endPos = rayTarget / m_localScaling;
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beginPos += m_localOrigin;
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endPos += m_localOrigin;
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ProcessTrianglesAction processTriangles;
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processTriangles.shape = this;
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processTriangles.flipQuadEdges = m_flipQuadEdges;
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processTriangles.useDiamondSubdivision = m_useDiamondSubdivision;
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processTriangles.callback = callback;
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processTriangles.width = m_heightStickWidth - 1;
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processTriangles.length = m_heightStickLength - 1;
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// TODO Transform vectors to account for m_upAxis
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int iBeginX = static_cast<int>(floor(beginPos[0]));
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int iBeginZ = static_cast<int>(floor(beginPos[2]));
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int iEndX = static_cast<int>(floor(endPos[0]));
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int iEndZ = static_cast<int>(floor(endPos[2]));
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if (iBeginX == iEndX && iBeginZ == iEndZ)
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{
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// The ray will never cross quads within the plane,
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// so directly process triangles within one quad
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// (typically, vertical rays should end up here)
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processTriangles.exec(iBeginX, iEndZ);
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return;
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}
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if (m_vboundsGrid == NULL)
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{
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// Process all quads intersecting the flat projection of the ray
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gridRaycast(processTriangles, beginPos, endPos);
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}
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else
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{
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btVector3 rayDiff = endPos - beginPos;
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btScalar flatDistance2 = rayDiff[0] * rayDiff[0] + rayDiff[2] * rayDiff[2];
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if (flatDistance2 < m_vboundsChunkSize * m_vboundsChunkSize)
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{
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// Don't use chunks, the ray is too short in the plane
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gridRaycast(processTriangles, beginPos, endPos);
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}
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ProcessVBoundsAction processVBounds;
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processVBounds.width = m_vboundsGridWidth;
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processVBounds.length = m_vboundsGridLength;
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processVBounds.vbounds = m_vboundsGrid;
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processVBounds.rayBegin = beginPos;
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processVBounds.rayEnd = endPos;
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processVBounds.rayDir = rayDiff.normalized();
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processVBounds.processTriangles = processTriangles;
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processVBounds.chunkSize = m_vboundsChunkSize;
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// The ray is long, run raycast on a higher-level grid
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gridRaycast(processVBounds, beginPos / m_vboundsChunkSize, endPos / m_vboundsChunkSize);
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}
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}
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/// Builds a grid data structure storing the min and max heights of the terrain in chunks.
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/// if chunkSize is zero, that accelerator is removed.
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/// If you modify the heights, you need to rebuild this accelerator.
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void btHeightfieldTerrainShape::buildAccelerator(int chunkSize)
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|
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{
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if (chunkSize <= 0)
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{
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|
clearAccelerator();
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return;
|
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}
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m_vboundsChunkSize = chunkSize;
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int nChunksX = m_heightStickWidth / chunkSize;
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int nChunksZ = m_heightStickLength / chunkSize;
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if (m_heightStickWidth % chunkSize > 0)
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++nChunksX; // In case terrain size isn't dividable by chunk size
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|
|
if (m_heightStickLength % chunkSize > 0)
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|
|
++nChunksZ;
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|
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|
|
if(m_vboundsGridWidth != nChunksX || m_vboundsGridLength != nChunksZ)
|
|
|
|
|
{
|
|
|
|
|
clearAccelerator();
|
|
|
|
|
m_vboundsGridWidth = nChunksX;
|
|
|
|
|
m_vboundsGridLength = nChunksZ;
|
|
|
|
|
}
|
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|
|
|
|
|
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|
|
if (nChunksX == 0 || nChunksZ == 0)
|
|
|
|
|
return;
|
|
|
|
|
|
|
|
|
|
// TODO What is the recommended way to allocate this?
|
|
|
|
|
// This data structure is only reallocated if the required size changed
|
|
|
|
|
if (m_vboundsGrid == NULL)
|
|
|
|
|
m_vboundsGrid = new Range[nChunksX * nChunksZ];
|
|
|
|
|
|
|
|
|
|
// Compute min and max height for all chunks
|
|
|
|
|
for (int cz = 0; cz < nChunksZ; ++cz)
|
|
|
|
|
{
|
|
|
|
|
int z0 = cz * chunkSize;
|
|
|
|
|
|
|
|
|
|
for (int cx = 0; cx < nChunksX; ++cx)
|
|
|
|
|
{
|
|
|
|
|
int x0 = cx * chunkSize;
|
|
|
|
|
|
|
|
|
|
Range r;
|
|
|
|
|
|
|
|
|
|
r.min = getRawHeightFieldValue(x0, z0);
|
|
|
|
|
r.max = r.min;
|
|
|
|
|
|
|
|
|
|
// Compute min and max height for this chunk.
|
|
|
|
|
// We have to include one extra cell to account for neighbors.
|
|
|
|
|
// Here is why:
|
|
|
|
|
// Say we have a flat terrain, and a plateau that fits a chunk perfectly.
|
|
|
|
|
//
|
|
|
|
|
// Left Right
|
|
|
|
|
// 0---0---0---1---1---1
|
|
|
|
|
// | | | | | |
|
|
|
|
|
// 0---0---0---1---1---1
|
|
|
|
|
// | | | | | |
|
|
|
|
|
// 0---0---0---1---1---1
|
|
|
|
|
// x
|
|
|
|
|
//
|
|
|
|
|
// If the AABB for the Left chunk did not share vertices with the Right,
|
|
|
|
|
// then we would fail collision tests at x due to a gap.
|
|
|
|
|
//
|
|
|
|
|
for (int z = z0; z < z0 + chunkSize + 1; ++z)
|
|
|
|
|
{
|
|
|
|
|
if (z >= m_heightStickLength)
|
|
|
|
|
continue;
|
|
|
|
|
|
|
|
|
|
for (int x = x0; x < x0 + chunkSize + 1; ++x)
|
|
|
|
|
{
|
|
|
|
|
if (x >= m_heightStickWidth)
|
|
|
|
|
continue;
|
|
|
|
|
|
|
|
|
|
btScalar height = getRawHeightFieldValue(x, z);
|
|
|
|
|
|
|
|
|
|
if (height < r.min)
|
|
|
|
|
r.min = height;
|
|
|
|
|
else if (height > r.max)
|
|
|
|
|
r.max = height;
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
m_vboundsGrid[cx + cz * nChunksX] = r;
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
void btHeightfieldTerrainShape::clearAccelerator()
|
|
|
|
|
{
|
|
|
|
|
if (m_vboundsGrid)
|
|
|
|
|
{
|
|
|
|
|
// TODO What is the recommended way to deallocate this?
|
|
|
|
|
delete[] m_vboundsGrid;
|
|
|
|
|
m_vboundsGrid = 0;
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Rémi Verschelde