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Diffstat (limited to 'src/mbgl/algorithm/update_tile_masks.hpp')
| -rw-r--r-- | src/mbgl/algorithm/update_tile_masks.hpp | 128 |
1 files changed, 128 insertions, 0 deletions
diff --git a/src/mbgl/algorithm/update_tile_masks.hpp b/src/mbgl/algorithm/update_tile_masks.hpp new file mode 100644 index 0000000000..a7840cd163 --- /dev/null +++ b/src/mbgl/algorithm/update_tile_masks.hpp @@ -0,0 +1,128 @@ +#pragma once + +#include <mbgl/renderer/tile_mask.hpp> + +#include <vector> +#include <functional> +#include <algorithm> + +namespace mbgl { +namespace algorithm { + +namespace { + +template <typename Renderable> +void computeTileMasks( + const CanonicalTileID& root, + const UnwrappedTileID ref, + typename std::vector<std::reference_wrapper<Renderable>>::const_iterator it, + const typename std::vector<std::reference_wrapper<Renderable>>::const_iterator end, + TileMask& mask) { + // If the reference or any of its children is found in the list, we need to recurse. + for (; it != end; ++it) { + auto& renderable = it->get(); + if (!renderable.used) { + continue; + } + if (ref == renderable.id) { + // The current tile is masked out, so we don't need to add them to the mask set. + return; + } else if (renderable.id.isChildOf(ref)) { + // There's at least one child tile that is masked out, so recursively descend. + for (const auto& child : ref.children()) { + computeTileMasks<Renderable>(root, child, it, end, mask); + } + return; + } + } + + // We couldn't find a child, so it's definitely a masked part. + // Compute the difference between the root tile ID and the reference tile ID, since TileMask + // elements are always relative (see below for explanation). + const uint8_t diffZ = ref.canonical.z - root.z; + mask.emplace(diffZ, ref.canonical.x - (root.x << diffZ), ref.canonical.y - (root.y << diffZ)); +} + +} // namespace + +// Updates the TileMasks for all renderables. Renderables are objects that have an UnwrappedTileID +// property indicating where they should be rendered on the screen. A TileMask describes all regions +// within that tile that are *not* covered by other Renderables. +// Example: Renderables in our list are 2/1/3, 3/3/6, and 4/5/13. The schematic for creating the +// TileMask for 2/1/3 looks like this: +// +// ┌────────┬────────┬─────────────────┐ +// │ │ │#################│ +// │ 4/4/12 │ 4/5/12 │#################│ +// │ │ │#################│ +// ├──────3/2/6──────┤#####3/3/6#######│ +// │ │########│#################│ +// │ 4/4/13 │#4/5/13#│#################│ +// │ │########│#################│ +// ├────────┴──────2/1/3───────────────┤ +// │ │ │ +// │ │ │ +// │ │ │ +// │ 3/2/7 │ 3/3/7 │ +// │ │ │ +// │ │ │ +// │ │ │ +// └─────────────────┴─────────────────┘ +// +// The TileMask for 2/1/3 thus consists of the tiles 4/4/12, 4/5/12, 4/4/13, 3/2/7, and 3/3/7, +// but it does *not* include 4/5/13, and 3/3/6, since these are other Renderables. +// A TileMask always contains TileIDs *relative* to the tile it is generated for, so 2/1/3 is +// "subtracted" from these TileIDs. The final TileMask for 2/1/3 will thus be: +// +// ┌────────┬────────┬─────────────────┐ +// │ │ │#################│ +// │ 2/0/0 │ 2/1/0 │#################│ +// │ │ │#################│ +// ├────────┼────────┤#################│ +// │ │########│#################│ +// │ 2/0/1 │########│#################│ +// │ │########│#################│ +// ├────────┴────────┼─────────────────┤ +// │ │ │ +// │ │ │ +// │ │ │ +// │ 1/0/1 │ 1/1/1 │ +// │ │ │ +// │ │ │ +// │ │ │ +// └─────────────────┴─────────────────┘ +// +// Only other Renderables that are *children* of the Renderable we are generating the mask for will +// be considered. For example, adding a Renderable with TileID 4/8/13 won't affect the TileMask for +// 2/1/3, since it is not a descendant of it. +template <typename Renderable> +void updateTileMasks(std::vector<std::reference_wrapper<Renderable>> renderables) { + std::sort(renderables.begin(), renderables.end(), + [](const Renderable& a, const Renderable& b) { return a.id < b.id; }); + + TileMask mask; + const auto end = renderables.end(); + for (auto it = renderables.begin(); it != end; it++) { + auto& renderable = it->get(); + if (!renderable.used) { + continue; + } + // Try to add all remaining ids as children. We sorted the tile list + // by z earlier, so all preceding items cannot be children of the current + // tile. We also compute the lower bound of the next wrap, because items of the next wrap + // can never be children of the current wrap. + auto child_it = std::next(it); + const auto children_end = std::lower_bound( + child_it, end, + UnwrappedTileID{ static_cast<int16_t>(renderable.id.wrap + 1), { 0, 0, 0 } }, + [](auto& a, auto& b) { return a.get().id < b; }); + + mask.clear(); + computeTileMasks<Renderable>(renderable.id.canonical, renderable.id, child_it, children_end, + mask); + renderable.setMask(std::move(mask)); + } +} + +} // namespace algorithm +} // namespace mbgl |