mirror of
https://github.com/godotengine/godot.git
synced 2024-12-21 10:25:24 +08:00
e2cc0e484e
The Godot-specific patch is just a single line now; removing this patch will likely require adjusting Godot importer code to handle error limits better. This also adds new SIMPLIFY_ options; Godot is currently not using any of these but might use SIMPLIFY_PRUNE and SIMPLIFY_SPARSE in the future.
297 lines
7.6 KiB
C++
297 lines
7.6 KiB
C++
// This file is part of meshoptimizer library; see meshoptimizer.h for version/license details
|
|
#include "meshoptimizer.h"
|
|
|
|
#include <assert.h>
|
|
#include <limits.h>
|
|
#include <string.h>
|
|
|
|
// This work is based on:
|
|
// Francine Evans, Steven Skiena and Amitabh Varshney. Optimizing Triangle Strips for Fast Rendering. 1996
|
|
namespace meshopt
|
|
{
|
|
|
|
static unsigned int findStripFirst(const unsigned int buffer[][3], unsigned int buffer_size, const unsigned char* valence)
|
|
{
|
|
unsigned int index = 0;
|
|
unsigned int iv = ~0u;
|
|
|
|
for (size_t i = 0; i < buffer_size; ++i)
|
|
{
|
|
unsigned char va = valence[buffer[i][0]], vb = valence[buffer[i][1]], vc = valence[buffer[i][2]];
|
|
unsigned int v = (va < vb && va < vc) ? va : (vb < vc ? vb : vc);
|
|
|
|
if (v < iv)
|
|
{
|
|
index = unsigned(i);
|
|
iv = v;
|
|
}
|
|
}
|
|
|
|
return index;
|
|
}
|
|
|
|
static int findStripNext(const unsigned int buffer[][3], unsigned int buffer_size, unsigned int e0, unsigned int e1)
|
|
{
|
|
for (size_t i = 0; i < buffer_size; ++i)
|
|
{
|
|
unsigned int a = buffer[i][0], b = buffer[i][1], c = buffer[i][2];
|
|
|
|
if (e0 == a && e1 == b)
|
|
return (int(i) << 2) | 2;
|
|
else if (e0 == b && e1 == c)
|
|
return (int(i) << 2) | 0;
|
|
else if (e0 == c && e1 == a)
|
|
return (int(i) << 2) | 1;
|
|
}
|
|
|
|
return -1;
|
|
}
|
|
|
|
} // namespace meshopt
|
|
|
|
size_t meshopt_stripify(unsigned int* destination, const unsigned int* indices, size_t index_count, size_t vertex_count, unsigned int restart_index)
|
|
{
|
|
assert(destination != indices);
|
|
assert(index_count % 3 == 0);
|
|
|
|
using namespace meshopt;
|
|
|
|
meshopt_Allocator allocator;
|
|
|
|
const size_t buffer_capacity = 8;
|
|
|
|
unsigned int buffer[buffer_capacity][3] = {};
|
|
unsigned int buffer_size = 0;
|
|
|
|
size_t index_offset = 0;
|
|
|
|
unsigned int strip[2] = {};
|
|
unsigned int parity = 0;
|
|
|
|
size_t strip_size = 0;
|
|
|
|
// compute vertex valence; this is used to prioritize starting triangle for strips
|
|
// note: we use 8-bit counters for performance; for outlier vertices the valence is incorrect but that just affects the heuristic
|
|
unsigned char* valence = allocator.allocate<unsigned char>(vertex_count);
|
|
memset(valence, 0, vertex_count);
|
|
|
|
for (size_t i = 0; i < index_count; ++i)
|
|
{
|
|
unsigned int index = indices[i];
|
|
assert(index < vertex_count);
|
|
|
|
valence[index]++;
|
|
}
|
|
|
|
int next = -1;
|
|
|
|
while (buffer_size > 0 || index_offset < index_count)
|
|
{
|
|
assert(next < 0 || (size_t(next >> 2) < buffer_size && (next & 3) < 3));
|
|
|
|
// fill triangle buffer
|
|
while (buffer_size < buffer_capacity && index_offset < index_count)
|
|
{
|
|
buffer[buffer_size][0] = indices[index_offset + 0];
|
|
buffer[buffer_size][1] = indices[index_offset + 1];
|
|
buffer[buffer_size][2] = indices[index_offset + 2];
|
|
|
|
buffer_size++;
|
|
index_offset += 3;
|
|
}
|
|
|
|
assert(buffer_size > 0);
|
|
|
|
if (next >= 0)
|
|
{
|
|
unsigned int i = next >> 2;
|
|
unsigned int a = buffer[i][0], b = buffer[i][1], c = buffer[i][2];
|
|
unsigned int v = buffer[i][next & 3];
|
|
|
|
// ordered removal from the buffer
|
|
memmove(buffer[i], buffer[i + 1], (buffer_size - i - 1) * sizeof(buffer[0]));
|
|
buffer_size--;
|
|
|
|
// update vertex valences for strip start heuristic
|
|
valence[a]--;
|
|
valence[b]--;
|
|
valence[c]--;
|
|
|
|
// find next triangle (note that edge order flips on every iteration)
|
|
// in some cases we need to perform a swap to pick a different outgoing triangle edge
|
|
// for [a b c], the default strip edge is [b c], but we might want to use [a c]
|
|
int cont = findStripNext(buffer, buffer_size, parity ? strip[1] : v, parity ? v : strip[1]);
|
|
int swap = cont < 0 ? findStripNext(buffer, buffer_size, parity ? v : strip[0], parity ? strip[0] : v) : -1;
|
|
|
|
if (cont < 0 && swap >= 0)
|
|
{
|
|
// [a b c] => [a b a c]
|
|
destination[strip_size++] = strip[0];
|
|
destination[strip_size++] = v;
|
|
|
|
// next strip has same winding
|
|
// ? a b => b a v
|
|
strip[1] = v;
|
|
|
|
next = swap;
|
|
}
|
|
else
|
|
{
|
|
// emit the next vertex in the strip
|
|
destination[strip_size++] = v;
|
|
|
|
// next strip has flipped winding
|
|
strip[0] = strip[1];
|
|
strip[1] = v;
|
|
parity ^= 1;
|
|
|
|
next = cont;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
// if we didn't find anything, we need to find the next new triangle
|
|
// we use a heuristic to maximize the strip length
|
|
unsigned int i = findStripFirst(buffer, buffer_size, valence);
|
|
unsigned int a = buffer[i][0], b = buffer[i][1], c = buffer[i][2];
|
|
|
|
// ordered removal from the buffer
|
|
memmove(buffer[i], buffer[i + 1], (buffer_size - i - 1) * sizeof(buffer[0]));
|
|
buffer_size--;
|
|
|
|
// update vertex valences for strip start heuristic
|
|
valence[a]--;
|
|
valence[b]--;
|
|
valence[c]--;
|
|
|
|
// we need to pre-rotate the triangle so that we will find a match in the existing buffer on the next iteration
|
|
int ea = findStripNext(buffer, buffer_size, c, b);
|
|
int eb = findStripNext(buffer, buffer_size, a, c);
|
|
int ec = findStripNext(buffer, buffer_size, b, a);
|
|
|
|
// in some cases we can have several matching edges; since we can pick any edge, we pick the one with the smallest
|
|
// triangle index in the buffer. this reduces the effect of stripification on ACMR and additionally - for unclear
|
|
// reasons - slightly improves the stripification efficiency
|
|
int mine = INT_MAX;
|
|
mine = (ea >= 0 && mine > ea) ? ea : mine;
|
|
mine = (eb >= 0 && mine > eb) ? eb : mine;
|
|
mine = (ec >= 0 && mine > ec) ? ec : mine;
|
|
|
|
if (ea == mine)
|
|
{
|
|
// keep abc
|
|
next = ea;
|
|
}
|
|
else if (eb == mine)
|
|
{
|
|
// abc -> bca
|
|
unsigned int t = a;
|
|
a = b, b = c, c = t;
|
|
|
|
next = eb;
|
|
}
|
|
else if (ec == mine)
|
|
{
|
|
// abc -> cab
|
|
unsigned int t = c;
|
|
c = b, b = a, a = t;
|
|
|
|
next = ec;
|
|
}
|
|
|
|
if (restart_index)
|
|
{
|
|
if (strip_size)
|
|
destination[strip_size++] = restart_index;
|
|
|
|
destination[strip_size++] = a;
|
|
destination[strip_size++] = b;
|
|
destination[strip_size++] = c;
|
|
|
|
// new strip always starts with the same edge winding
|
|
strip[0] = b;
|
|
strip[1] = c;
|
|
parity = 1;
|
|
}
|
|
else
|
|
{
|
|
if (strip_size)
|
|
{
|
|
// connect last strip using degenerate triangles
|
|
destination[strip_size++] = strip[1];
|
|
destination[strip_size++] = a;
|
|
}
|
|
|
|
// note that we may need to flip the emitted triangle based on parity
|
|
// we always end up with outgoing edge "cb" in the end
|
|
unsigned int e0 = parity ? c : b;
|
|
unsigned int e1 = parity ? b : c;
|
|
|
|
destination[strip_size++] = a;
|
|
destination[strip_size++] = e0;
|
|
destination[strip_size++] = e1;
|
|
|
|
strip[0] = e0;
|
|
strip[1] = e1;
|
|
parity ^= 1;
|
|
}
|
|
}
|
|
}
|
|
|
|
return strip_size;
|
|
}
|
|
|
|
size_t meshopt_stripifyBound(size_t index_count)
|
|
{
|
|
assert(index_count % 3 == 0);
|
|
|
|
// worst case without restarts is 2 degenerate indices and 3 indices per triangle
|
|
// worst case with restarts is 1 restart index and 3 indices per triangle
|
|
return (index_count / 3) * 5;
|
|
}
|
|
|
|
size_t meshopt_unstripify(unsigned int* destination, const unsigned int* indices, size_t index_count, unsigned int restart_index)
|
|
{
|
|
assert(destination != indices);
|
|
|
|
size_t offset = 0;
|
|
size_t start = 0;
|
|
|
|
for (size_t i = 0; i < index_count; ++i)
|
|
{
|
|
if (restart_index && indices[i] == restart_index)
|
|
{
|
|
start = i + 1;
|
|
}
|
|
else if (i - start >= 2)
|
|
{
|
|
unsigned int a = indices[i - 2], b = indices[i - 1], c = indices[i];
|
|
|
|
// flip winding for odd triangles
|
|
if ((i - start) & 1)
|
|
{
|
|
unsigned int t = a;
|
|
a = b, b = t;
|
|
}
|
|
|
|
// although we use restart indices, strip swaps still produce degenerate triangles, so skip them
|
|
if (a != b && a != c && b != c)
|
|
{
|
|
destination[offset + 0] = a;
|
|
destination[offset + 1] = b;
|
|
destination[offset + 2] = c;
|
|
offset += 3;
|
|
}
|
|
}
|
|
}
|
|
|
|
return offset;
|
|
}
|
|
|
|
size_t meshopt_unstripifyBound(size_t index_count)
|
|
{
|
|
assert(index_count == 0 || index_count >= 3);
|
|
|
|
return (index_count == 0) ? 0 : (index_count - 2) * 3;
|
|
}
|