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clusterizer: Extract neighbor triangle selection into a function
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This cleans up the code a little bit and makes it easier to extend the high
level algorithm. This change by itself doesn't change the clusterization
output.
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@zeux
zeux committed Nov 23, 2022
1 parent 5baa38e commit 7d03762
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Showing 2 changed files with 64 additions and 57 deletions.
2 changes: 1 addition & 1 deletion demo/main.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1213,7 +1213,7 @@ void processDev(const char* path)
if (!loadMesh(mesh, path))
return;

tessellationAdjacency(mesh);
meshlets(mesh, false);
}

int main(int argc, char** argv)
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119 changes: 63 additions & 56 deletions src/clusterizer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -283,6 +283,67 @@ static bool appendMeshlet(meshopt_Meshlet& meshlet, unsigned int a, unsigned int
return result;
}

static unsigned int getNeighborTriangle(const meshopt_Meshlet& meshlet, const Cone& meshlet_cone, unsigned int* meshlet_vertices, const unsigned int* indices, const TriangleAdjacency2& adjacency, const Cone* triangles, const unsigned int* live_triangles, const unsigned char* used, float meshlet_expected_radius, float cone_weight, unsigned int* out_extra)
{
unsigned int best_triangle = ~0u;
unsigned int best_extra = 5;
float best_score = FLT_MAX;

for (size_t i = 0; i < meshlet.vertex_count; ++i)
{
unsigned int index = meshlet_vertices[meshlet.vertex_offset + i];

unsigned int* neighbours = &adjacency.data[0] + adjacency.offsets[index];
size_t neighbours_size = adjacency.counts[index];

for (size_t j = 0; j < neighbours_size; ++j)
{
unsigned int triangle = neighbours[j];
unsigned int a = indices[triangle * 3 + 0], b = indices[triangle * 3 + 1], c = indices[triangle * 3 + 2];

unsigned int extra = (used[a] == 0xff) + (used[b] == 0xff) + (used[c] == 0xff);

// triangles that don't add new vertices to meshlets are max. priority
if (extra != 0)
{
// artificially increase the priority of dangling triangles as they're expensive to add to new meshlets
if (live_triangles[a] == 1 || live_triangles[b] == 1 || live_triangles[c] == 1)
extra = 0;

extra++;
}

// since topology-based priority is always more important than the score, we can skip scoring in some cases
if (extra > best_extra)
continue;

const Cone& tri_cone = triangles[triangle];

float distance2 =
(tri_cone.px - meshlet_cone.px) * (tri_cone.px - meshlet_cone.px) +
(tri_cone.py - meshlet_cone.py) * (tri_cone.py - meshlet_cone.py) +
(tri_cone.pz - meshlet_cone.pz) * (tri_cone.pz - meshlet_cone.pz);

float spread = tri_cone.nx * meshlet_cone.nx + tri_cone.ny * meshlet_cone.ny + tri_cone.nz * meshlet_cone.nz;

float score = getMeshletScore(distance2, spread, cone_weight, meshlet_expected_radius);

// note that topology-based priority is always more important than the score
// this helps maintain reasonable effectiveness of meshlet data and reduces scoring cost
if (extra < best_extra || score < best_score)
{
best_triangle = triangle;
best_extra = extra;
best_score = score;
}
}
}

*out_extra = best_extra;

return best_triangle;
}

struct KDNode
{
union
Expand Down Expand Up @@ -511,64 +572,10 @@ size_t meshopt_buildMeshlets(meshopt_Meshlet* meshlets, unsigned int* meshlet_ve

for (;;)
{
unsigned int best_triangle = ~0u;
unsigned int best_extra = 5;
float best_score = FLT_MAX;

Cone meshlet_cone = getMeshletCone(meshlet_cone_acc, meshlet.triangle_count);

for (size_t i = 0; i < meshlet.vertex_count; ++i)
{
unsigned int index = meshlet_vertices[meshlet.vertex_offset + i];

unsigned int* neighbours = &adjacency.data[0] + adjacency.offsets[index];
size_t neighbours_size = adjacency.counts[index];

for (size_t j = 0; j < neighbours_size; ++j)
{
unsigned int triangle = neighbours[j];
assert(!emitted_flags[triangle]);

unsigned int a = indices[triangle * 3 + 0], b = indices[triangle * 3 + 1], c = indices[triangle * 3 + 2];
assert(a < vertex_count && b < vertex_count && c < vertex_count);

unsigned int extra = (used[a] == 0xff) + (used[b] == 0xff) + (used[c] == 0xff);

// triangles that don't add new vertices to meshlets are max. priority
if (extra != 0)
{
// artificially increase the priority of dangling triangles as they're expensive to add to new meshlets
if (live_triangles[a] == 1 || live_triangles[b] == 1 || live_triangles[c] == 1)
extra = 0;

extra++;
}

// since topology-based priority is always more important than the score, we can skip scoring in some cases
if (extra > best_extra)
continue;

const Cone& tri_cone = triangles[triangle];

float distance2 =
(tri_cone.px - meshlet_cone.px) * (tri_cone.px - meshlet_cone.px) +
(tri_cone.py - meshlet_cone.py) * (tri_cone.py - meshlet_cone.py) +
(tri_cone.pz - meshlet_cone.pz) * (tri_cone.pz - meshlet_cone.pz);

float spread = tri_cone.nx * meshlet_cone.nx + tri_cone.ny * meshlet_cone.ny + tri_cone.nz * meshlet_cone.nz;

float score = getMeshletScore(distance2, spread, cone_weight, meshlet_expected_radius);

// note that topology-based priority is always more important than the score
// this helps maintain reasonable effectiveness of meshlet data and reduces scoring cost
if (extra < best_extra || score < best_score)
{
best_triangle = triangle;
best_extra = extra;
best_score = score;
}
}
}
unsigned int best_extra = 0;
unsigned int best_triangle = getNeighborTriangle(meshlet, meshlet_cone, meshlet_vertices, indices, adjacency, triangles, live_triangles, used, meshlet_expected_radius, cone_weight, &best_extra);

if (best_triangle == ~0u)
{
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