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#include "ChunkMeshing.hpp"
namespace MC::World::Generation::ChunkMeshing {
Chunk::BlockData get_block_wrapping(const Chunk& chunk, const ChunkNeighbors& neighbors, Vector<3, I32> pos) {
const Chunk* chunk_to_ask;
auto overflow = [](I32& c, I32 max) -> I8 {
if (c < 0) { c += max; return -1; }
if (c >= max) { c -= max; return 1; }
return 0;
};
auto xo = overflow(pos.x(), Chunk::Width);
auto yo = overflow(pos.y(), Chunk::Height);
auto zo = overflow(pos.z(), Chunk::Width);
// Blocks above and below a chunk are always Air.
if (yo != 0) return {};
if (xo == 1 && zo == 1) { chunk_to_ask = neighbors.south_east; }
else if (xo == 1 && zo == -1) { chunk_to_ask = neighbors.north_east; }
else if (xo == -1 && zo == 1) { chunk_to_ask = neighbors.south_west; }
else if (xo == -1 && zo == -1) { chunk_to_ask = neighbors.north_west; }
else if (xo == 1) { chunk_to_ask = neighbors.east; }
else if (xo == -1) { chunk_to_ask = neighbors.west; }
else if (zo == 1) { chunk_to_ask = neighbors.south; }
else if (zo == -1) { chunk_to_ask = neighbors.north; }
else { chunk_to_ask = &chunk; }
return chunk_to_ask->get(pos.x(), pos.y(), pos.z());
}
std::array<Vector<2, F32>, 4> face_tex_coords(BlockType type, BlockSide side) {
U8 atlas_width = 4;
U8 atlas_height = 4;
Real width_step = 1.0f / atlas_width;
Real height_step = 1.0f / atlas_height;
auto block_coords = [=](U8 x, U8 y) -> std::array<Vector<2, F32>, 4> {
auto t = y * height_step;
auto l = x * width_step;
auto b = t + height_step;
auto r = l + width_step;
// This is horrible and it was better before I restructured the vertex order...
// In the last version the front and back side pairs had the same structure in different winding,
// so a back_side check wasn't needed...
// Note: BlockSide::Front counts as a back side, because OpenGL has an inverted Z-axis compared to us.
Bool back_side = side == BlockSide::Front || side == BlockSide::Bottom || side == BlockSide::Left;
if (back_side) {
return {{{l, t}, {l, b}, {r, b}, {r, t}}};
}
return {{{r, t}, {l, t}, {l, b}, {r, b}}};
};
switch (type) {
case BlockType::Dirt:
return block_coords(1, 0);
case BlockType::Grass:
switch (side) {
case BlockSide::Front:
case BlockSide::Back:
case BlockSide::Left:
case BlockSide::Right:
return block_coords(2, 0);
case BlockSide::Bottom:
return block_coords(1, 0);
case BlockSide::Top:
return block_coords(0, 0);
}
case BlockType::Stone:
return block_coords(3, 0);
case BlockType::Sand:
return block_coords(1, 1);
case BlockType::Water:
return block_coords(0, 1);
case BlockType::Snow:
switch (side) {
case BlockSide::Front:
case BlockSide::Back:
case BlockSide::Left:
case BlockSide::Right:
return block_coords(3, 1);
case BlockSide::Bottom:
return block_coords(1, 0);
case BlockSide::Top:
return block_coords(2, 1);
}
case BlockType::Wood:
switch (side) {
case BlockSide::Front:
case BlockSide::Back:
case BlockSide::Right:
case BlockSide::Left:
return block_coords(0, 2);
case BlockSide::Bottom:
case BlockSide::Top:
return block_coords(1, 2);
}
case BlockType::Leaves:
return block_coords(2, 2);
case BlockType::Air:
return {};
}
}
std::array<Vector<3, F32>, 4> face_normals(BlockSide side) {
auto is_side = [=](BlockSide s) -> Real { return s == side; };
Vector<3, F32> normal = {
is_side(BlockSide::Right) - is_side(BlockSide::Left),
is_side(BlockSide::Top) - is_side(BlockSide::Bottom),
is_side(BlockSide::Front) - is_side(BlockSide::Back),
};
return {normal, normal, normal, normal};
}
std::array<F32, 4> face_ao_values(Chunk& chunk, const ChunkNeighbors& neighbors, U32 x, U32 y, U32 z, BlockSide side) {
std::array<Vector<3, I32>, 8> offsets{};
// Given a block position, these offsets can be added to it to get the 8 blocks necessary to calculate AO.
// There are 4 corners and 4 sides, corners are visually distinguished by the lack of spaces and
// but you can recognize them by the fact that they have no 0 offsets.
// Note: Is there a way to compute these? I tried but I couldn't... If the vertex windings ever change again I don't want to hardcode these...
auto nowhere = Vector<3, I32>::max();
switch (side) {
case BlockSide::Front:
offsets = {{{0, 1, 1}, {-1,1,1}, {-1, 0, 1}, {-1,-1,1}, {0, -1, 1}, {1,-1,1}, {1, 0, 1}, {1,1,1}}};
break;
case BlockSide::Back:
offsets = {{{-1, 0, -1}, {-1,1,-1}, {0, 1, -1}, {1,1,-1}, {1, 0, -1}, {1,-1,-1}, {0, -1, -1}, {-1,-1,-1}}};
break;
case BlockSide::Top:
offsets = {{{-1, 1, 0}, {-1,1,1}, {0, 1, 1}, {1,1,1}, {1, 1, 0}, {1,1,-1}, {0, 1, -1}, {-1,1,-1}}};
break;
case BlockSide::Bottom:
offsets = {{{0, -1, 1}, {-1,-1,1}, {-1, -1, 0}, {-1,-1,-1}, {0, -1, -1}, {1,-1,-1}, {1, -1, 0}, {1,-1,1}}};
break;
case BlockSide::Right:
offsets = {{{1, 0, -1}, {1,1,-1}, {1, 1, 0}, {1,1,1}, {1, 0, 1}, {1,-1,1}, {1, -1, 0}, {1,-1,-1}}};
break;
case BlockSide::Left:
offsets = {{{-1, 1, 0}, {-1,1,-1}, {-1, 0, -1}, {-1,-1,-1}, {-1, -1, 0}, {-1,-1,1}, {-1, 0, 1}, {-1,1,1}}};
break;
}
std::array<F32, 4> vertex_ao{};
UInt offset_index = 0;
for (UInt vertex = 0; vertex < 4; vertex++) {
auto a = offsets[offset_index];
auto b = offsets[++offset_index]; // corner
auto c = offsets[++offset_index % 8];
auto block_a = get_block_wrapping(chunk, neighbors, {x + a.x(), y + a.y(), z + a.z()});
auto block_b = get_block_wrapping(chunk, neighbors, {x + b.x(), y + b.y(), z + b.z()});
auto block_c = get_block_wrapping(chunk, neighbors, {x + c.x(), y + c.y(), z + c.z()});
F32 occlusion_a = block_a.empty() ? 0 : 1;
F32 occlusion_b = block_b.empty() ? 0 : 1;
F32 occlusion_c = block_c.empty() ? 0 : 1;
if (occlusion_a + occlusion_c == 2.0f) {
vertex_ao[vertex] = 1.0f;
} else {
vertex_ao[vertex] = (occlusion_a + occlusion_b + occlusion_c) / 3;
}
}
return vertex_ao;
}
Bool is_face_visible(Chunk& chunk, const ChunkNeighbors& neighbors, U32 x, U32 y, U32 z, BlockSide side) {
Vector<3, I32> offset{};
switch (side) {
case BlockSide::Front:
offset[2] = 1;
break;
case BlockSide::Back:
offset[2] = -1;
break;
case BlockSide::Top:
offset[1] = 1;
break;
case BlockSide::Bottom:
offset[1] = -1;
break;
case BlockSide::Right:
offset[0] = 1;
break;
case BlockSide::Left:
offset[0] = -1;
break;
}
Vector<3, I32> neighbor_pos{
x + offset.x(), y + offset.y(), z + offset.z(),
};
auto [neighbor] = get_block_wrapping(chunk, neighbors, neighbor_pos);
return neighbor.is_transparent();
}
GFX::Mesh create_mesh_for_chunk(Chunk& chunk, const ChunkNeighbors& neighbors) {
std::vector<Vector<3, F32>> positions{};
std::vector<Vector<3, F32>> normals{};
std::vector<Vector<2, F32>> tex_coords{};
std::vector<F32> ambient_occlusion_values{};
std::vector<U32> indices{};
for (Int x = 0; x < Chunk::Width; x++) {
for (Int y = 0; y < Chunk::Height; y++) {
for (Int z = 0; z < Chunk::Width; z++) {
auto block = chunk.get(x, y, z);
if (block.empty())
continue;
for (auto side: BlockSide::all()) {
if (!is_face_visible(chunk, neighbors, x, y, z, side))
continue;
auto side_positions = side.face();
auto side_normals = face_normals(side);
auto side_tex_coords = face_tex_coords(block.type, side);
auto side_ao = face_ao_values(chunk, neighbors, x, y, z, side);
for (auto& position : side_positions) {
position = position + Vector<3, F32>{x, y, z};
}
U32 s = positions.size();
positions.insert(positions.end(), side_positions.begin(), side_positions.end());
normals.insert(normals.end(), side_normals.begin(), side_normals.end());
tex_coords.insert(tex_coords.end(), side_tex_coords.begin(), side_tex_coords.end());
ambient_occlusion_values.insert(ambient_occlusion_values.end(), side_ao.begin(), side_ao.end());
indices.insert(indices.end(), {s + 0, s + 1, s + 2, s + 2, s + 3, s + 0 });
}
}
}
}
return {
{positions, normals, tex_coords, ambient_occlusion_values},
indices,
};
}
}
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