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#include "StarCollisionGenerator.hpp"
namespace Star {
void CollisionGenerator::init(CollisionKindAccessor accessor) {
m_accessor = accessor;
}
List<CollisionBlock> CollisionGenerator::getBlocks(RectI const& region) const {
if (region.isNull())
return {};
List<CollisionBlock> list;
populateCollisionBuffer(region);
getBlocksMarchingSquares(list, region, CollisionKind::Dynamic);
getBlocksPlatforms(list, region, CollisionKind::Platform);
return list;
}
void CollisionGenerator::getBlocksPlatforms(List<CollisionBlock>& list, RectI const& region, CollisionKind kind) const {
int xMin = region.xMin();
int xMax = region.xMax();
int yMin = region.yMin();
int yMax = region.yMax();
for (int x = xMin; x < xMax; ++x) {
for (int y = yMin; y < yMax; ++y) {
if (collisionKind(x, y) == kind) {
auto addBlock = [&](PolyF::VertexList vertices) {
CollisionBlock block;
block.space = Vec2I(x, y);
block.kind = kind;
block.poly = PolyF(std::move(vertices));
block.polyBounds = block.poly.boundBox();
list.append(std::move(block));
};
// This was once simple and elegant and made sense but then I made it
// match the actual platform rendering more closely and now it's a big
// shitty pile of special cases again. RIP.
bool right = collisionKind(x + 1, y) == kind;
bool left = collisionKind(x - 1, y) == kind;
bool downRight = collisionKind(x + 1, y - 1) == kind && collisionKind(x + 1, y) != kind;
bool downLeft = collisionKind(x - 1, y - 1) == kind && collisionKind(x - 1, y) != kind;
bool upRight = collisionKind(x + 1, y + 1) == kind && !left && !right;
bool upLeft = collisionKind(x - 1, y + 1) == kind && !left && !right;
bool above = collisionKind(x, y + 1) == kind;
bool below = collisionKind(x, y - 1) == kind;
if (downRight && downLeft && upRight && upLeft) {
addBlock({Vec2F(x, y), Vec2F(x + 1, y + 1)});
addBlock({Vec2F(x + 1, y), Vec2F(x, y + 1)});
} else if (above && below) {
addBlock({Vec2F(x, y + 1), Vec2F(x + 1, y + 1)});
} else if (upLeft && downLeft && !upRight && !downRight) {
addBlock({Vec2F(x + 1, y), Vec2F(x, y + 1)});
} else if (upRight && downRight && !upLeft && !upRight) {
addBlock({Vec2F(x, y), Vec2F(x + 1, y + 1)});
} else if (upRight && downLeft) {
addBlock({Vec2F(x, y), Vec2F(x + 1, y + 1)});
// special case block for connecting flat platform above
if (above && collisionKind(x + 1, y + 1) == kind)
addBlock({Vec2F(x + 1, y + 1), Vec2F(x + 2, y + 2)});
} else if (upLeft && downRight) {
addBlock({Vec2F(x + 1, y), Vec2F(x, y + 1)});
// special case block for connecting flat platform above
if (above && collisionKind(x - 1, y + 1) == kind)
addBlock({Vec2F(x, y + 1), Vec2F(x - 1, y + 2)});
} else if (above && !downRight && !downLeft) {
addBlock({Vec2F(x, y + 1), Vec2F(x + 1, y + 1)});
} else if (upLeft && !upRight) {
addBlock({Vec2F(x + 1, y), Vec2F(x, y + 1)});
} else if (upRight && !upLeft) {
addBlock({Vec2F(x, y), Vec2F(x + 1, y + 1)});
} else if (downRight && (left || !below)) {
addBlock({Vec2F(x + 1, y), Vec2F(x, y + 1)});
} else if (downLeft && (right || !below)) {
addBlock({Vec2F(x, y), Vec2F(x + 1, y + 1)});
} else {
addBlock({Vec2F(x, y + 1), Vec2F(x + 1, y + 1)});
}
}
}
}
}
void CollisionGenerator::getBlocksMarchingSquares(List<CollisionBlock>& list, RectI const& region, CollisionKind kind) const {
// uses binary masking to assign each group of 4 tiles a value between 0 and 15
// with corners ul = 1, ur = 2, lr = 4, ll = 8
// points spaced at 0.5 around the edge of a 1x1 square, clockwise from bottom left,
// plus the center point for special cases
static Vec2F const msv[9] = {
Vec2F(0.5, 0.5),
Vec2F(0.5, 1.0),
Vec2F(0.5, 1.5),
Vec2F(1.0, 1.5),
Vec2F(1.5, 1.5),
Vec2F(1.5, 1.0),
Vec2F(1.5, 0.5),
Vec2F(1.0, 0.5),
Vec2F(1.0, 1.0)
};
// refers to vertex offset indices in msv, with 8 being no vertex
static unsigned const msp[22][6] = {
{9, 9, 9, 9, 9, 9},
{1, 2, 3, 9, 9, 9},
{3, 4, 5, 9, 9, 9},
{1, 2, 4, 5, 9, 9},
{7, 5, 6, 9, 9, 9},
{1, 2, 3, 5, 6, 7},
{7, 3, 4, 6, 9, 9},
{1, 2, 4, 6, 7, 9},
{0, 1, 7, 9, 9, 9},
{0, 2, 3, 7, 9, 9},
{0, 1, 3, 4, 5, 7},
{0, 2, 4, 5, 7, 9},
{0, 1, 5, 6, 9, 9},
{0, 2, 3, 5, 6, 9},
{0, 1, 3, 4, 6, 9},
{0, 2, 4, 6, 9, 9},
// special cases for squared off top corners
{5, 6, 7, 8, 9, 9}, // top left corner
{0, 1, 8, 7, 9, 9}, // top right corner
// special cases for hollowed out bottom corners
{0, 2, 3, 8, 9, 9}, // lower left corner part 1
{0, 8, 5, 6, 9, 9}, // lower left corner part 2
{0, 1, 8, 6, 9, 9}, // lower right corner part 1
{6, 8, 3, 4, 9, 9} // lower right corner part 2
};
auto addBlock = [&](int x, int y, uint8_t svi) {
CollisionBlock block;
block.space = Vec2I(x, y);
block.poly.clear();
for (auto i : msp[svi]) {
if (i == 9)
break;
block.poly.add(Vec2F(x, y) + msv[i]);
}
block.polyBounds = block.poly.boundBox();
block.kind = std::max({collisionKind(x, y), collisionKind(x + 1, y), collisionKind(x, y + 1), collisionKind(x + 1, y + 1)});
list.append(std::move(block));
};
int xMin = region.xMin();
int xMax = region.xMax();
int yMin = region.yMin();
int yMax = region.yMax();
for (int x = xMin; x < xMax; ++x) {
for (int y = yMin; y < yMax; ++y) {
uint8_t neighborMask = 0;
if (collisionKind(x, y + 1) >= kind)
neighborMask |= 1;
if (collisionKind(x + 1, y + 1) >= kind)
neighborMask |= 2;
if (collisionKind(x + 1, y) >= kind)
neighborMask |= 4;
if (collisionKind(x, y) >= kind)
neighborMask |= 8;
if (neighborMask == 4) {
if (collisionKind(x + 2, y) >= kind &&
collisionKind(x + 2, y + 1) < kind &&
collisionKind(x, y - 1) < kind) {
addBlock(x, y, 16);
continue;
}
} else if (neighborMask == 8) {
if (collisionKind(x - 1, y) >= kind &&
collisionKind(x - 1, y + 1) < kind &&
collisionKind(x + 1, y - 1) < kind) {
addBlock(x, y, 17);
continue;
}
} else if (neighborMask == 13) {
if (collisionKind(x, y + 2) >= kind &&
collisionKind(x + 1, y + 2) < kind &&
collisionKind(x + 2, y) >= kind) {
addBlock(x, y, 18);
addBlock(x, y, 19);
continue;
}
} else if (neighborMask == 14) {
if (collisionKind(x, y + 2) < kind &&
collisionKind(x + 1, y + 2) >= kind &&
collisionKind(x - 1, y) >= kind) {
addBlock(x, y, 20);
addBlock(x, y, 21);
continue;
}
}
if (neighborMask != 0)
addBlock(x, y, neighborMask);
}
}
}
void CollisionGenerator::populateCollisionBuffer(RectI const& region) const {
int xmin = region.xMin() - BlockInfluenceRadius;
int ymin = region.yMin() - BlockInfluenceRadius;
int xmax = region.xMax() + BlockInfluenceRadius;
int ymax = region.yMax() + BlockInfluenceRadius;
m_collisionBufferCorner = {xmin, ymin};
m_collisionBuffer.resize(xmax - xmin, ymax - ymin);
for (int x = xmin; x < xmax; ++x)
for (int y = ymin; y < ymax; ++y)
m_collisionBuffer(x - xmin, y - ymin) = m_accessor(x, y);
}
CollisionKind CollisionGenerator::collisionKind(int x, int y) const {
return m_collisionBuffer(x - m_collisionBufferCorner[0], y - m_collisionBufferCorner[1]);
}
}
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