MuJoCo Web Viewer: add web client containing code that runs in the browser

PiperOrigin-RevId: 956698568
Change-Id: Ia4bebcb25b488d255994018da03e9115187b890c

python/mujoco/experimental/studio/web/state_payload.cc

@@ -46,6 +46,7 @@ void AppendStateBlock(std::vector<std::byte>& buffer, uint32_t tag,
 }
 
 // Serializes the render state (exactly kRenderStateSize bytes) into `ptr`.
+// Must copy the same fields in the same order as ParseRenderState.
 void SerializeRenderStateInto(std::byte* ptr, const mjvCamera& camera,
                               const mjvPerturb& perturb,
                               const mjvOption& vis_options, const mjOption& opt,
@@ -78,6 +79,32 @@ void SerializeRenderStateInto(std::byte* ptr, const mjvCamera& camera,
 
 }  // namespace
 
+// Parses a render state block produced by SerializeStatePayload.
+// Must copy the same fields in the same order as SerializeRenderStateInto.
+void ParseRenderState(const std::byte* data, RenderStateView* out) {
+  const std::byte* ptr = data;
+
+  memcpy(&out->camera, ptr, sizeof(mjvCamera));
+  ptr += sizeof(mjvCamera);
+
+  memcpy(&out->perturb, ptr, sizeof(mjvPerturb));
+  ptr += sizeof(mjvPerturb);
+
+  memcpy(&out->vis_options, ptr, sizeof(mjvOption));
+  ptr += sizeof(mjvOption);
+
+  memcpy(&out->opt, ptr, sizeof(mjOption));
+  ptr += sizeof(mjOption);
+
+  memcpy(&out->vis, ptr, sizeof(mjVisual));
+  ptr += sizeof(mjVisual);
+
+  memcpy(&out->stat, ptr, sizeof(mjStatistic));
+  ptr += sizeof(mjStatistic);
+
+  memcpy(out->render_flags, ptr, mjNRNDFLAG);
+}
+
 size_t MaxStatePayloadSize(size_t physics_bytes) {
   return sizeof(StatePayloadHeader) + 3 * sizeof(StateBlockHeader) +
          (sizeof(int32_t) + physics_bytes) + kRenderStateSize +