godot/thirdparty/meshoptimizer/indexcodec.cpp
K. S. Ernest (iFire) Lee 59b61a1f64 Scale error in mesh optimizer so it uses absolute scale.
Switch to simplify sloppy for another try.

Update to meshoptimizer e3f53f66e7a35b9b8764bee478589d79e34fa698.
2021-01-11 06:07:54 -08:00

675 lines
20 KiB
C++

// This file is part of meshoptimizer library; see meshoptimizer.h for version/license details
#include "meshoptimizer.h"
#include <assert.h>
#include <string.h>
// This work is based on:
// Fabian Giesen. Simple lossless index buffer compression & follow-up. 2013
// Conor Stokes. Vertex Cache Optimised Index Buffer Compression. 2014
namespace meshopt
{
const unsigned char kIndexHeader = 0xe0;
const unsigned char kSequenceHeader = 0xd0;
static int gEncodeIndexVersion = 0;
typedef unsigned int VertexFifo[16];
typedef unsigned int EdgeFifo[16][2];
static const unsigned int kTriangleIndexOrder[3][3] = {
{0, 1, 2},
{1, 2, 0},
{2, 0, 1},
};
static const unsigned char kCodeAuxEncodingTable[16] = {
0x00, 0x76, 0x87, 0x56, 0x67, 0x78, 0xa9, 0x86, 0x65, 0x89, 0x68, 0x98, 0x01, 0x69,
0, 0, // last two entries aren't used for encoding
};
static int rotateTriangle(unsigned int a, unsigned int b, unsigned int c, unsigned int next)
{
(void)a;
return (b == next) ? 1 : (c == next) ? 2 : 0;
}
static int getEdgeFifo(EdgeFifo fifo, unsigned int a, unsigned int b, unsigned int c, size_t offset)
{
for (int i = 0; i < 16; ++i)
{
size_t index = (offset - 1 - i) & 15;
unsigned int e0 = fifo[index][0];
unsigned int e1 = fifo[index][1];
if (e0 == a && e1 == b)
return (i << 2) | 0;
if (e0 == b && e1 == c)
return (i << 2) | 1;
if (e0 == c && e1 == a)
return (i << 2) | 2;
}
return -1;
}
static void pushEdgeFifo(EdgeFifo fifo, unsigned int a, unsigned int b, size_t& offset)
{
fifo[offset][0] = a;
fifo[offset][1] = b;
offset = (offset + 1) & 15;
}
static int getVertexFifo(VertexFifo fifo, unsigned int v, size_t offset)
{
for (int i = 0; i < 16; ++i)
{
size_t index = (offset - 1 - i) & 15;
if (fifo[index] == v)
return i;
}
return -1;
}
static void pushVertexFifo(VertexFifo fifo, unsigned int v, size_t& offset, int cond = 1)
{
fifo[offset] = v;
offset = (offset + cond) & 15;
}
static void encodeVByte(unsigned char*& data, unsigned int v)
{
// encode 32-bit value in up to 5 7-bit groups
do
{
*data++ = (v & 127) | (v > 127 ? 128 : 0);
v >>= 7;
} while (v);
}
static unsigned int decodeVByte(const unsigned char*& data)
{
unsigned char lead = *data++;
// fast path: single byte
if (lead < 128)
return lead;
// slow path: up to 4 extra bytes
// note that this loop always terminates, which is important for malformed data
unsigned int result = lead & 127;
unsigned int shift = 7;
for (int i = 0; i < 4; ++i)
{
unsigned char group = *data++;
result |= unsigned(group & 127) << shift;
shift += 7;
if (group < 128)
break;
}
return result;
}
static void encodeIndex(unsigned char*& data, unsigned int index, unsigned int last)
{
unsigned int d = index - last;
unsigned int v = (d << 1) ^ (int(d) >> 31);
encodeVByte(data, v);
}
static unsigned int decodeIndex(const unsigned char*& data, unsigned int last)
{
unsigned int v = decodeVByte(data);
unsigned int d = (v >> 1) ^ -int(v & 1);
return last + d;
}
static int getCodeAuxIndex(unsigned char v, const unsigned char* table)
{
for (int i = 0; i < 16; ++i)
if (table[i] == v)
return i;
return -1;
}
static void writeTriangle(void* destination, size_t offset, size_t index_size, unsigned int a, unsigned int b, unsigned int c)
{
if (index_size == 2)
{
static_cast<unsigned short*>(destination)[offset + 0] = (unsigned short)(a);
static_cast<unsigned short*>(destination)[offset + 1] = (unsigned short)(b);
static_cast<unsigned short*>(destination)[offset + 2] = (unsigned short)(c);
}
else
{
static_cast<unsigned int*>(destination)[offset + 0] = a;
static_cast<unsigned int*>(destination)[offset + 1] = b;
static_cast<unsigned int*>(destination)[offset + 2] = c;
}
}
} // namespace meshopt
size_t meshopt_encodeIndexBuffer(unsigned char* buffer, size_t buffer_size, const unsigned int* indices, size_t index_count)
{
using namespace meshopt;
assert(index_count % 3 == 0);
// the minimum valid encoding is header, 1 byte per triangle and a 16-byte codeaux table
if (buffer_size < 1 + index_count / 3 + 16)
return 0;
int version = gEncodeIndexVersion;
buffer[0] = (unsigned char)(kIndexHeader | version);
EdgeFifo edgefifo;
memset(edgefifo, -1, sizeof(edgefifo));
VertexFifo vertexfifo;
memset(vertexfifo, -1, sizeof(vertexfifo));
size_t edgefifooffset = 0;
size_t vertexfifooffset = 0;
unsigned int next = 0;
unsigned int last = 0;
unsigned char* code = buffer + 1;
unsigned char* data = code + index_count / 3;
unsigned char* data_safe_end = buffer + buffer_size - 16;
int fecmax = version >= 1 ? 13 : 15;
// use static encoding table; it's possible to pack the result and then build an optimal table and repack
// for now we keep it simple and use the table that has been generated based on symbol frequency on a training mesh set
const unsigned char* codeaux_table = kCodeAuxEncodingTable;
for (size_t i = 0; i < index_count; i += 3)
{
// make sure we have enough space to write a triangle
// each triangle writes at most 16 bytes: 1b for codeaux and 5b for each free index
// after this we can be sure we can write without extra bounds checks
if (data > data_safe_end)
return 0;
int fer = getEdgeFifo(edgefifo, indices[i + 0], indices[i + 1], indices[i + 2], edgefifooffset);
if (fer >= 0 && (fer >> 2) < 15)
{
const unsigned int* order = kTriangleIndexOrder[fer & 3];
unsigned int a = indices[i + order[0]], b = indices[i + order[1]], c = indices[i + order[2]];
// encode edge index and vertex fifo index, next or free index
int fe = fer >> 2;
int fc = getVertexFifo(vertexfifo, c, vertexfifooffset);
int fec = (fc >= 1 && fc < fecmax) ? fc : (c == next) ? (next++, 0) : 15;
if (fec == 15 && version >= 1)
{
// encode last-1 and last+1 to optimize strip-like sequences
if (c + 1 == last)
fec = 13, last = c;
if (c == last + 1)
fec = 14, last = c;
}
*code++ = (unsigned char)((fe << 4) | fec);
// note that we need to update the last index since free indices are delta-encoded
if (fec == 15)
encodeIndex(data, c, last), last = c;
// we only need to push third vertex since first two are likely already in the vertex fifo
if (fec == 0 || fec >= fecmax)
pushVertexFifo(vertexfifo, c, vertexfifooffset);
// we only need to push two new edges to edge fifo since the third one is already there
pushEdgeFifo(edgefifo, c, b, edgefifooffset);
pushEdgeFifo(edgefifo, a, c, edgefifooffset);
}
else
{
int rotation = rotateTriangle(indices[i + 0], indices[i + 1], indices[i + 2], next);
const unsigned int* order = kTriangleIndexOrder[rotation];
unsigned int a = indices[i + order[0]], b = indices[i + order[1]], c = indices[i + order[2]];
// if a/b/c are 0/1/2, we emit a reset code
bool reset = false;
if (a == 0 && b == 1 && c == 2 && next > 0 && version >= 1)
{
reset = true;
next = 0;
// reset vertex fifo to make sure we don't accidentally reference vertices from that in the future
// this makes sure next continues to get incremented instead of being stuck
memset(vertexfifo, -1, sizeof(vertexfifo));
}
int fb = getVertexFifo(vertexfifo, b, vertexfifooffset);
int fc = getVertexFifo(vertexfifo, c, vertexfifooffset);
// after rotation, a is almost always equal to next, so we don't waste bits on FIFO encoding for a
int fea = (a == next) ? (next++, 0) : 15;
int feb = (fb >= 0 && fb < 14) ? (fb + 1) : (b == next) ? (next++, 0) : 15;
int fec = (fc >= 0 && fc < 14) ? (fc + 1) : (c == next) ? (next++, 0) : 15;
// we encode feb & fec in 4 bits using a table if possible, and as a full byte otherwise
unsigned char codeaux = (unsigned char)((feb << 4) | fec);
int codeauxindex = getCodeAuxIndex(codeaux, codeaux_table);
// <14 encodes an index into codeaux table, 14 encodes fea=0, 15 encodes fea=15
if (fea == 0 && codeauxindex >= 0 && codeauxindex < 14 && !reset)
{
*code++ = (unsigned char)((15 << 4) | codeauxindex);
}
else
{
*code++ = (unsigned char)((15 << 4) | 14 | fea);
*data++ = codeaux;
}
// note that we need to update the last index since free indices are delta-encoded
if (fea == 15)
encodeIndex(data, a, last), last = a;
if (feb == 15)
encodeIndex(data, b, last), last = b;
if (fec == 15)
encodeIndex(data, c, last), last = c;
// only push vertices that weren't already in fifo
if (fea == 0 || fea == 15)
pushVertexFifo(vertexfifo, a, vertexfifooffset);
if (feb == 0 || feb == 15)
pushVertexFifo(vertexfifo, b, vertexfifooffset);
if (fec == 0 || fec == 15)
pushVertexFifo(vertexfifo, c, vertexfifooffset);
// all three edges aren't in the fifo; pushing all of them is important so that we can match them for later triangles
pushEdgeFifo(edgefifo, b, a, edgefifooffset);
pushEdgeFifo(edgefifo, c, b, edgefifooffset);
pushEdgeFifo(edgefifo, a, c, edgefifooffset);
}
}
// make sure we have enough space to write codeaux table
if (data > data_safe_end)
return 0;
// add codeaux encoding table to the end of the stream; this is used for decoding codeaux *and* as padding
// we need padding for decoding to be able to assume that each triangle is encoded as <= 16 bytes of extra data
// this is enough space for aux byte + 5 bytes per varint index which is the absolute worst case for any input
for (size_t i = 0; i < 16; ++i)
{
// decoder assumes that table entries never refer to separately encoded indices
assert((codeaux_table[i] & 0xf) != 0xf && (codeaux_table[i] >> 4) != 0xf);
*data++ = codeaux_table[i];
}
// since we encode restarts as codeaux without a table reference, we need to make sure 00 is encoded as a table reference
assert(codeaux_table[0] == 0);
assert(data >= buffer + index_count / 3 + 16);
assert(data <= buffer + buffer_size);
return data - buffer;
}
size_t meshopt_encodeIndexBufferBound(size_t index_count, size_t vertex_count)
{
assert(index_count % 3 == 0);
// compute number of bits required for each index
unsigned int vertex_bits = 1;
while (vertex_bits < 32 && vertex_count > size_t(1) << vertex_bits)
vertex_bits++;
// worst-case encoding is 2 header bytes + 3 varint-7 encoded index deltas
unsigned int vertex_groups = (vertex_bits + 1 + 6) / 7;
return 1 + (index_count / 3) * (2 + 3 * vertex_groups) + 16;
}
void meshopt_encodeIndexVersion(int version)
{
assert(unsigned(version) <= 1);
meshopt::gEncodeIndexVersion = version;
}
int meshopt_decodeIndexBuffer(void* destination, size_t index_count, size_t index_size, const unsigned char* buffer, size_t buffer_size)
{
using namespace meshopt;
assert(index_count % 3 == 0);
assert(index_size == 2 || index_size == 4);
// the minimum valid encoding is header, 1 byte per triangle and a 16-byte codeaux table
if (buffer_size < 1 + index_count / 3 + 16)
return -2;
if ((buffer[0] & 0xf0) != kIndexHeader)
return -1;
int version = buffer[0] & 0x0f;
if (version > 1)
return -1;
EdgeFifo edgefifo;
memset(edgefifo, -1, sizeof(edgefifo));
VertexFifo vertexfifo;
memset(vertexfifo, -1, sizeof(vertexfifo));
size_t edgefifooffset = 0;
size_t vertexfifooffset = 0;
unsigned int next = 0;
unsigned int last = 0;
int fecmax = version >= 1 ? 13 : 15;
// since we store 16-byte codeaux table at the end, triangle data has to begin before data_safe_end
const unsigned char* code = buffer + 1;
const unsigned char* data = code + index_count / 3;
const unsigned char* data_safe_end = buffer + buffer_size - 16;
const unsigned char* codeaux_table = data_safe_end;
for (size_t i = 0; i < index_count; i += 3)
{
// make sure we have enough data to read for a triangle
// each triangle reads at most 16 bytes of data: 1b for codeaux and 5b for each free index
// after this we can be sure we can read without extra bounds checks
if (data > data_safe_end)
return -2;
unsigned char codetri = *code++;
if (codetri < 0xf0)
{
int fe = codetri >> 4;
// fifo reads are wrapped around 16 entry buffer
unsigned int a = edgefifo[(edgefifooffset - 1 - fe) & 15][0];
unsigned int b = edgefifo[(edgefifooffset - 1 - fe) & 15][1];
int fec = codetri & 15;
// note: this is the most common path in the entire decoder
// inside this if we try to stay branchless (by using cmov/etc.) since these aren't predictable
if (fec < fecmax)
{
// fifo reads are wrapped around 16 entry buffer
unsigned int cf = vertexfifo[(vertexfifooffset - 1 - fec) & 15];
unsigned int c = (fec == 0) ? next : cf;
int fec0 = fec == 0;
next += fec0;
// output triangle
writeTriangle(destination, i, index_size, a, b, c);
// push vertex/edge fifo must match the encoding step *exactly* otherwise the data will not be decoded correctly
pushVertexFifo(vertexfifo, c, vertexfifooffset, fec0);
pushEdgeFifo(edgefifo, c, b, edgefifooffset);
pushEdgeFifo(edgefifo, a, c, edgefifooffset);
}
else
{
unsigned int c = 0;
// fec - (fec ^ 3) decodes 13, 14 into -1, 1
// note that we need to update the last index since free indices are delta-encoded
last = c = (fec != 15) ? last + (fec - (fec ^ 3)) : decodeIndex(data, last);
// output triangle
writeTriangle(destination, i, index_size, a, b, c);
// push vertex/edge fifo must match the encoding step *exactly* otherwise the data will not be decoded correctly
pushVertexFifo(vertexfifo, c, vertexfifooffset);
pushEdgeFifo(edgefifo, c, b, edgefifooffset);
pushEdgeFifo(edgefifo, a, c, edgefifooffset);
}
}
else
{
// fast path: read codeaux from the table
if (codetri < 0xfe)
{
unsigned char codeaux = codeaux_table[codetri & 15];
// note: table can't contain feb/fec=15
int feb = codeaux >> 4;
int fec = codeaux & 15;
// fifo reads are wrapped around 16 entry buffer
// also note that we increment next for all three vertices before decoding indices - this matches encoder behavior
unsigned int a = next++;
unsigned int bf = vertexfifo[(vertexfifooffset - feb) & 15];
unsigned int b = (feb == 0) ? next : bf;
int feb0 = feb == 0;
next += feb0;
unsigned int cf = vertexfifo[(vertexfifooffset - fec) & 15];
unsigned int c = (fec == 0) ? next : cf;
int fec0 = fec == 0;
next += fec0;
// output triangle
writeTriangle(destination, i, index_size, a, b, c);
// push vertex/edge fifo must match the encoding step *exactly* otherwise the data will not be decoded correctly
pushVertexFifo(vertexfifo, a, vertexfifooffset);
pushVertexFifo(vertexfifo, b, vertexfifooffset, feb0);
pushVertexFifo(vertexfifo, c, vertexfifooffset, fec0);
pushEdgeFifo(edgefifo, b, a, edgefifooffset);
pushEdgeFifo(edgefifo, c, b, edgefifooffset);
pushEdgeFifo(edgefifo, a, c, edgefifooffset);
}
else
{
// slow path: read a full byte for codeaux instead of using a table lookup
unsigned char codeaux = *data++;
int fea = codetri == 0xfe ? 0 : 15;
int feb = codeaux >> 4;
int fec = codeaux & 15;
// reset: codeaux is 0 but encoded as not-a-table
if (codeaux == 0)
next = 0;
// fifo reads are wrapped around 16 entry buffer
// also note that we increment next for all three vertices before decoding indices - this matches encoder behavior
unsigned int a = (fea == 0) ? next++ : 0;
unsigned int b = (feb == 0) ? next++ : vertexfifo[(vertexfifooffset - feb) & 15];
unsigned int c = (fec == 0) ? next++ : vertexfifo[(vertexfifooffset - fec) & 15];
// note that we need to update the last index since free indices are delta-encoded
if (fea == 15)
last = a = decodeIndex(data, last);
if (feb == 15)
last = b = decodeIndex(data, last);
if (fec == 15)
last = c = decodeIndex(data, last);
// output triangle
writeTriangle(destination, i, index_size, a, b, c);
// push vertex/edge fifo must match the encoding step *exactly* otherwise the data will not be decoded correctly
pushVertexFifo(vertexfifo, a, vertexfifooffset);
pushVertexFifo(vertexfifo, b, vertexfifooffset, (feb == 0) | (feb == 15));
pushVertexFifo(vertexfifo, c, vertexfifooffset, (fec == 0) | (fec == 15));
pushEdgeFifo(edgefifo, b, a, edgefifooffset);
pushEdgeFifo(edgefifo, c, b, edgefifooffset);
pushEdgeFifo(edgefifo, a, c, edgefifooffset);
}
}
}
// we should've read all data bytes and stopped at the boundary between data and codeaux table
if (data != data_safe_end)
return -3;
return 0;
}
size_t meshopt_encodeIndexSequence(unsigned char* buffer, size_t buffer_size, const unsigned int* indices, size_t index_count)
{
using namespace meshopt;
// the minimum valid encoding is header, 1 byte per index and a 4-byte tail
if (buffer_size < 1 + index_count + 4)
return 0;
int version = gEncodeIndexVersion;
buffer[0] = (unsigned char)(kSequenceHeader | version);
unsigned int last[2] = {};
unsigned int current = 0;
unsigned char* data = buffer + 1;
unsigned char* data_safe_end = buffer + buffer_size - 4;
for (size_t i = 0; i < index_count; ++i)
{
// make sure we have enough data to write
// each index writes at most 5 bytes of data; there's a 4 byte tail after data_safe_end
// after this we can be sure we can write without extra bounds checks
if (data >= data_safe_end)
return 0;
unsigned int index = indices[i];
// this is a heuristic that switches between baselines when the delta grows too large
// we want the encoded delta to fit into one byte (7 bits), but 2 bits are used for sign and baseline index
// for now we immediately switch the baseline when delta grows too large - this can be adjusted arbitrarily
int cd = int(index - last[current]);
current ^= ((cd < 0 ? -cd : cd) >= 30);
// encode delta from the last index
unsigned int d = index - last[current];
unsigned int v = (d << 1) ^ (int(d) >> 31);
// note: low bit encodes the index of the last baseline which will be used for reconstruction
encodeVByte(data, (v << 1) | current);
// update last for the next iteration that uses it
last[current] = index;
}
// make sure we have enough space to write tail
if (data > data_safe_end)
return 0;
for (int k = 0; k < 4; ++k)
*data++ = 0;
return data - buffer;
}
size_t meshopt_encodeIndexSequenceBound(size_t index_count, size_t vertex_count)
{
// compute number of bits required for each index
unsigned int vertex_bits = 1;
while (vertex_bits < 32 && vertex_count > size_t(1) << vertex_bits)
vertex_bits++;
// worst-case encoding is 1 varint-7 encoded index delta for a K bit value and an extra bit
unsigned int vertex_groups = (vertex_bits + 1 + 1 + 6) / 7;
return 1 + index_count * vertex_groups + 4;
}
int meshopt_decodeIndexSequence(void* destination, size_t index_count, size_t index_size, const unsigned char* buffer, size_t buffer_size)
{
using namespace meshopt;
// the minimum valid encoding is header, 1 byte per index and a 4-byte tail
if (buffer_size < 1 + index_count + 4)
return -2;
if ((buffer[0] & 0xf0) != kSequenceHeader)
return -1;
int version = buffer[0] & 0x0f;
if (version > 1)
return -1;
const unsigned char* data = buffer + 1;
const unsigned char* data_safe_end = buffer + buffer_size - 4;
unsigned int last[2] = {};
for (size_t i = 0; i < index_count; ++i)
{
// make sure we have enough data to read
// each index reads at most 5 bytes of data; there's a 4 byte tail after data_safe_end
// after this we can be sure we can read without extra bounds checks
if (data >= data_safe_end)
return -2;
unsigned int v = decodeVByte(data);
// decode the index of the last baseline
unsigned int current = v & 1;
v >>= 1;
// reconstruct index as a delta
unsigned int d = (v >> 1) ^ -int(v & 1);
unsigned int index = last[current] + d;
// update last for the next iteration that uses it
last[current] = index;
if (index_size == 2)
{
static_cast<unsigned short*>(destination)[i] = (unsigned short)(index);
}
else
{
static_cast<unsigned int*>(destination)[i] = index;
}
}
// we should've read all data bytes and stopped at the boundary between data and tail
if (data != data_safe_end)
return -3;
return 0;
}