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gltfpack: Implement support for constant tracks
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These can be compressed into a single input/output value, which is very
valuable for position/scale tracks and occasional constant rotationt
tracks.
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@zeux
zeux committed Jun 2, 2019
1 parent 3c4bc87 commit c819b60
Showing 1 changed file with 101 additions and 15 deletions.
116 changes: 101 additions & 15 deletions tools/gltfpack.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -836,7 +836,7 @@ std::string to_string(size_t v)
std::string to_string(float v)
{
char buf[512];
sprintf(buf, "%.7g", v);
sprintf(buf, "%.9g", v);
return buf;
}

Expand Down Expand Up @@ -1218,6 +1218,40 @@ void writeAccessor(std::string& json, size_t view, cgltf_type type, cgltf_compon
json += "}";
}

bool isTrackConstant(const cgltf_animation_sampler& sampler, cgltf_animation_path_type type)
{
const float tolerance_generic = 1e-4f;
const float tolerance_rotation = 1e-3f;

Attr first = {};
cgltf_accessor_read_float(sampler.output, 0, first.f, 4);

for (size_t i = 1; i < sampler.output->count; ++i)
{
Attr attr = {};
cgltf_accessor_read_float(sampler.output, i, attr.f, 4);

if (type == cgltf_animation_path_type_rotation)
{
float error = 1.f - fabsf(first.f[0] * attr.f[0] + first.f[1] * attr.f[1] + first.f[2] * attr.f[2] + first.f[3] * attr.f[3]);

if (error > tolerance_rotation)
return false;
}
else
{
float error = 0;
for (int k = 0; k < 4; ++k)
error += fabsf(attr.f[0] - first.f[0]);

if (error > tolerance_generic)
return false;
}
}

return true;
}

void resampleKeyframes(std::vector<Attr>& data, const cgltf_animation_sampler& sampler, cgltf_animation_path_type type, int frames, float mint, int freq)
{
assert(sampler.interpolation == cgltf_interpolation_type_linear);
Expand Down Expand Up @@ -1727,21 +1761,51 @@ bool process(Scene& scene, const Settings& settings, std::string& json, std::str
std::string json_samplers;
std::string json_channels;

float mint = 0, maxt = 0;
std::vector<const cgltf_animation_channel*> tracks;

for (size_t j = 0; j < animation.channels_count; ++j)
{
const cgltf_animation_channel& channel = animation.channels[j];
const cgltf_animation_sampler& sampler = *channel.sampler;

if (!channel.target_node || !node_keep[channel.target_node - data->nodes])
continue;

if (channel.target_path != cgltf_animation_path_type_translation && channel.target_path != cgltf_animation_path_type_rotation && channel.target_path != cgltf_animation_path_type_scale)
continue;

if (sampler.interpolation != cgltf_interpolation_type_linear)
continue;

tracks.push_back(&channel);
}

if (tracks.empty())
continue;

float mint = 0, maxt = 0;
bool needs_time = false;
bool needs_pose = false;

for (size_t j = 0; j < tracks.size(); ++j)
{
const cgltf_animation_channel& channel = *tracks[j];
const cgltf_animation_sampler& sampler = *channel.sampler;

mint = std::min(mint, sampler.input->min[0]);
maxt = std::max(maxt, sampler.input->max[0]);

bool tc = isTrackConstant(sampler, channel.target_path);

needs_time = needs_time || !tc;
needs_pose = needs_pose || tc;
}

int frames = std::max(1, int((maxt - mint) * settings.anim_freq + 0.5f));

size_t time_view = view_offset;

if (needs_time)
{
std::vector<float> time(frames);

Expand All @@ -1757,29 +1821,51 @@ bool process(Scene& scene, const Settings& settings, std::string& json, std::str
bytes_time += bin.size() - bin_offset;

comma(json_accessors);
writeAccessor(json_accessors, view_offset, cgltf_type_scalar, p, false, frames);
writeAccessor(json_accessors, view_offset, cgltf_type_scalar, p, false, frames, &time.front(), &time.back());

view_offset++;
}

size_t track_offset = 0;
size_t pose_view = view_offset;

for (size_t j = 0; j < animation.channels_count; ++j)
if (needs_pose)
{
const cgltf_animation_channel& channel = animation.channels[j];
const cgltf_animation_sampler& sampler = *channel.sampler;
std::vector<float> pose(1, mint);

if (!channel.target_node || !node_keep[channel.target_node - data->nodes])
continue;
size_t bin_offset = bin.size();
cgltf_component_type p = writeTimeStream(bin, pose);

if (channel.target_path != cgltf_animation_path_type_translation && channel.target_path != cgltf_animation_path_type_rotation && channel.target_path != cgltf_animation_path_type_scale)
continue;
comma(json_buffer_views);
writeBufferView(json_buffer_views, cgltf_buffer_view_type_invalid, 1, 4, bin_offset, bin.size() - bin_offset, false);

if (sampler.interpolation != cgltf_interpolation_type_linear)
continue;
bytes_time += bin.size() - bin_offset;

comma(json_accessors);
writeAccessor(json_accessors, view_offset, cgltf_type_scalar, p, false, 1, &pose.front(), &pose.back());

view_offset++;
}

size_t track_offset = 0;

for (size_t j = 0; j < tracks.size(); ++j)
{
const cgltf_animation_channel& channel = *tracks[j];
const cgltf_animation_sampler& sampler = *channel.sampler;

bool tc = isTrackConstant(sampler, channel.target_path);

std::vector<Attr> track;
resampleKeyframes(track, sampler, channel.target_path, frames, mint, settings.anim_freq);
if (tc)
{
Attr pose = {};
cgltf_accessor_read_float(sampler.output, 0, pose.f, 4);
track.push_back(pose);
}
else
{
resampleKeyframes(track, sampler, channel.target_path, frames, mint, settings.anim_freq);
}

size_t bin_offset = bin.size();
std::pair<std::pair<cgltf_component_type, cgltf_type>, size_t> p = writeKeyframeStream(bin, channel.target_path, track);
Expand All @@ -1798,7 +1884,7 @@ bool process(Scene& scene, const Settings& settings, std::string& json, std::str

comma(json_samplers);
json_samplers += "{\"input\":";
json_samplers += to_string(time_view);
json_samplers += to_string(tc ? pose_view : time_view);
json_samplers += ",\"output\":";
json_samplers += to_string(data_view);
json_samplers += "}";
Expand Down

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