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gltfpack: Switch from manual encodeExpShared to meshopt_encodeFilterExp

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This simplifies the code and keeps the output identical since the
encoding logic is the same.

Note that since the stride here is 12 bytes, we can't encode directly
from the source attribute data (we need to skip W), but we can encode
using aliased destination & source.
This commit is contained in:
Arseny Kapoulkine
2024-10-17 10:57:53 -07:00
parent 6f31640841
commit fe720e62d0
1 changed files with 7 additions and 36 deletions
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gltf/stream.cpp
+7 -36
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@@ -245,31 +245,6 @@ static void renormalizeWeights(uint8_t (&w)[4])
w[max] += uint8_t(255 - sum);
}
static void encodeExpShared(uint32_t v[3], const Attr& a, int bits)
{
// get exponents from all components
int ex, ey, ez;
frexp(a.f[0], &ex);
frexp(a.f[1], &ey);
frexp(a.f[2], &ez);
// use maximum exponent to encode values; this guarantees that mantissa is [-1, 1]
// note that we additionally scale the mantissa to make it a K-bit signed integer (K-1 bits for magnitude)
int exp = std::max(ex, std::max(ey, ez)) - (bits - 1);
// compute renormalized rounded mantissas for each component
int mx = int(ldexp(a.f[0], -exp) + (a.f[0] >= 0 ? 0.5f : -0.5f));
int my = int(ldexp(a.f[1], -exp) + (a.f[1] >= 0 ? 0.5f : -0.5f));
int mz = int(ldexp(a.f[2], -exp) + (a.f[2] >= 0 ? 0.5f : -0.5f));
int mmask = (1 << 24) - 1;
// encode exponent & mantissa into each resulting value
v[0] = (mx & mmask) | (unsigned(exp) << 24);
v[1] = (my & mmask) | (unsigned(exp) << 24);
v[2] = (mz & mmask) | (unsigned(exp) << 24);
}
static uint32_t encodeExpOne(float v, int bits, int min_exp = -100)
{
// extract exponent
@@ -839,23 +814,19 @@ StreamFormat writeKeyframeStream(std::string& bin, cgltf_animation_path_type typ
StreamFormat::Filter filter = settings.compressmore ? StreamFormat::Filter_Exp : StreamFormat::Filter_None;
int bits = (type == cgltf_animation_path_type_translation) ? settings.trn_bits : settings.scl_bits;
size_t offset = bin.size();
for (size_t i = 0; i < data.size(); ++i)
{
const Attr& a = data[i];
if (filter == StreamFormat::Filter_Exp)
{
uint32_t v[3];
encodeExpShared(v, a, bits);
bin.append(reinterpret_cast<const char*>(v), sizeof(v));
}
else
{
float v[3] = {a.f[0], a.f[1], a.f[2]};
bin.append(reinterpret_cast<const char*>(v), sizeof(v));
}
float v[3] = {a.f[0], a.f[1], a.f[2]};
bin.append(reinterpret_cast<const char*>(v), sizeof(v));
}
if (filter == StreamFormat::Filter_Exp)
meshopt_encodeFilterExp(&bin[offset], data.size(), 12, bits, reinterpret_cast<const float*>(&bin[offset]), meshopt_EncodeExpSharedVector);
StreamFormat format = {cgltf_type_vec3, cgltf_component_type_r_32f, false, 12, filter};
return format;
}