Fix animation processing interpolation bug, crash on no merc material (…

…#3794)

Fixes the issue with animations doing a full 180 degree rotation and
disappearing. The quaternions in the GLB export "flip", and when
interpolating animation frames in between a flip, we got bogus
quaternions.

Fixes #3786

Also fix a crash in `goalc` when using merc models without any
materials.

Co-authored-by: water111 <[email protected]>

goalc/build_actor/common/MercExtract.cpp

@@ -97,7 +97,6 @@ void extract(const std::string& name,
   out.new_model.max_draws = 0;
 
   auto process_normal_draw = [&](tfrag3::MercEffect& eff, int mat_idx, const tfrag3::MercDraw& d_) {
-    const auto& mat = model.materials[mat_idx];
     eff.all_draws.push_back(d_);
     auto& draw = eff.all_draws.back();
     draw.mode = gltf_util::make_default_draw_mode();
@@ -107,6 +106,8 @@ void extract(const std::string& name,
       draw.tree_tex_id = 0;
       return;
     }
+    const auto& mat = model.materials[mat_idx];
+
     int tex_idx = mat.pbrMetallicRoughness.baseColorTexture.index;
     if (tex_idx == -1) {
       lg::warn("Material {} has no texture, using default texture.", mat.name);
@@ -172,8 +173,8 @@ void extract(const std::string& name,
   };
 
   for (const auto& [mat_idx, d_] : draw_by_material) {
-    const auto& mat = model.materials[mat_idx];
-    if (!gltf_util::material_has_envmap(mat) || !gltf_util::envmap_is_valid(mat)) {
+    if (mat_idx < 0 || !gltf_util::material_has_envmap(model.materials[mat_idx]) ||
+        !gltf_util::envmap_is_valid(model.materials[mat_idx])) {
       process_normal_draw(e, mat_idx, d_);
     } else {
       envmap_eff.has_envmap = true;

goalc/build_actor/common/animation_processing.cpp

@@ -21,7 +21,8 @@ int find_max_joint(const tinygltf::Animation& anim, const std::map<int, int>& no
 template <typename T>
 std::vector<T> compute_keyframes(const std::vector<float>& times,
                                  const std::vector<T>& values,
-                                 float framerate) {
+                                 float framerate,
+                                 bool quaternion_interp) {
   std::vector<T> ret;
   ASSERT(!times.empty());
   ASSERT(times.size() == values.size());
@@ -36,8 +37,15 @@ std::vector<T> compute_keyframes(const std::vector<float>& times,
     }
 
     const float fraction = (t - times.at(i)) / (times.at(i + 1) - times.at(i));
-    ret.push_back(values.at(i) * (1.f - fraction) + values.at(i + 1) * fraction);
-    // lg::info("{} + {:.3f}, {}", i, fraction, ret.back().to_string_aligned());
+    if (quaternion_interp) {
+      float multiplier = 1;
+      if (values.at(i).dot(values.at(i + 1)) < 0) {
+        multiplier = -1;
+      }
+      ret.push_back(values.at(i) * (1.f - fraction) + values.at(i + 1) * fraction * multiplier);
+    } else {
+      ret.push_back(values.at(i) * (1.f - fraction) + values.at(i + 1) * fraction);
+    }
     t += 1.f / framerate;
   }
   return ret;
@@ -47,12 +55,13 @@ template <int n>
 std::vector<math::Vector<float, n>> extract_keyframed_gltf_vecn(
     const tinygltf::Model& model,
     const tinygltf::AnimationSampler& sampler,
-    float framerate) {
+    float framerate,
+    bool quaternion_interp) {
   std::vector<float> times = gltf_util::extract_floats(model, sampler.input);
   std::vector<math::Vector<float, n>> values =
       gltf_util::extract_vec<float, n>(model, sampler.output, TINYGLTF_COMPONENT_TYPE_FLOAT);
   ASSERT(times.size() == values.size());
-  return compute_keyframes(times, values, framerate);
+  return compute_keyframes(times, values, framerate, quaternion_interp);
 }
 }  // namespace
 
@@ -75,13 +84,13 @@ UncompressedJointAnim extract_anim_from_gltf(const tinygltf::Model& model,
     const auto& sampler = anim.samplers.at(channel.sampler);
     if (channel.target_path == "translation") {
       out.joints.at(channel_joint).trans_frames =
-          extract_keyframed_gltf_vecn<3>(model, sampler, framerate);
+          extract_keyframed_gltf_vecn<3>(model, sampler, framerate, false);
     } else if (channel.target_path == "rotation") {
       out.joints.at(channel_joint).quat_frames =
-          extract_keyframed_gltf_vecn<4>(model, sampler, framerate);
+          extract_keyframed_gltf_vecn<4>(model, sampler, framerate, true);
     } else if (channel.target_path == "scale") {
       out.joints.at(channel_joint).scale_frames =
-          extract_keyframed_gltf_vecn<3>(model, sampler, framerate);
+          extract_keyframed_gltf_vecn<3>(model, sampler, framerate, false);
     } else {
       lg::die("unknown target_path {}", channel.target_path);
     }