The --ids option now re-orders faces by charts and dumps a JSON file.

.gitignore

@@ -2,3 +2,4 @@ build
 *.png
 *.obj
 *.bin
+*.json

CMakeLists.txt

@@ -16,9 +16,9 @@ add_subdirectory(thekla)
 add_subdirectory(vendor/poshlib)
 
 if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
-    set(CMAKE_CXX_FLAGS "-fopenmp -std=c++11")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fopenmp -std=c++11")
 else()
-    set(CMAKE_CXX_FLAGS "-std=c++11")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
 endif()
 
 add_definitions(

aobaker.cpp

@@ -95,6 +95,11 @@ int aobaker_bake(
     printf("Atlas mesh has %d verts\n", output_mesh->vertex_count);
     printf("Atlas mesh has %d triangles\n", output_mesh->index_count / 3);
 
+    // Reorder faces according to their respective charts.
+    if (chartinfo) {
+        atlas_reorder_faces(output_mesh, "chartids.json");
+    }
+
     // Transform the data produced by the Thekla library.
     float* coordsdata = 0;
     float* normsdata = 0;

cmdline.c

@@ -16,7 +16,7 @@ int main(int argc, const char **argv)
     flag_int(&sizehint, "sizehint", "Controls resolution of atlas");
     flag_int(&nsamples, "nsamples", "Quality of ambient occlusion");
     flag_bool(&gbuffer, "gbuffer", "Generate diagnostic images");
-    flag_bool(&chartinfo, "ids", "Add a chart id to the alpha channel");
+    flag_bool(&chartinfo, "ids", "Group faces by charts, add alpha channel");
     flag_parse(argc, argv, "v" AOBAKER_VERSION, 1);
     char const* inmesh = flagset_singleton()->argv[0];
     return aobaker_bake(inmesh, outmesh, atlas, sizehint, nsamples, gbuffer,

thekla/thekla/thekla_atlas.cpp

@@ -1,18 +1,17 @@
-
 #include "thekla_atlas.h"
 
 #include <cfloat>
 #include <cstdio>
+#include <vector>
+#include <map>
 
 #include "nvmesh/halfedge/Edge.h"
 #include "nvmesh/halfedge/Mesh.h"
 #include "nvmesh/halfedge/Face.h"
 #include "nvmesh/halfedge/Vertex.h"
 #include "nvmesh/param/Atlas.h"
 #include "nvmesh/raster/Raster.h"
-
 #include "nvmath/Vector.inl"
-
 #include "nvcore/Array.inl"
 
 #define STB_IMAGE_WRITE_IMPLEMENTATION
@@ -21,7 +20,6 @@
 using namespace Thekla;
 using namespace nv;
 
-
 inline Atlas_Output_Mesh * set_error(Atlas_Error * error, Atlas_Error code) {
     if (error) *error = code;
     return NULL;
@@ -309,6 +307,44 @@ static bool idSolidCallback(
     return true;
 }
 
+void Thekla::atlas_reorder_faces(Atlas_Output_Mesh * atlas_mesh, const char* outputfile)
+{
+    printf("Writing %s...\n", outputfile);
+    std::map<int, std::vector<int> > chart_to_faces;
+    std::map<int, std::vector<int> >::const_iterator chart_iter;
+    int nfaces = atlas_mesh->index_count / 3;
+    for (int nface = 0; nface < nfaces; nface++) {
+        int a = atlas_mesh->index_array[nface * 3];
+        Atlas_Output_Vertex& v = atlas_mesh->vertex_array[a];
+        chart_to_faces[v.chart_index].push_back(nface);
+    }
+    FILE* json = fopen(outputfile, "wt");
+    putc('[', json);
+    chart_iter = chart_to_faces.begin();
+    int* indices = new int[nfaces * 3], *pindex = indices;
+    while (chart_iter != chart_to_faces.end()) {
+        const std::vector<int>& faces = chart_iter->second;
+        for (size_t i = 0; i < faces.size(); i++) {
+            int nface = faces[i];
+            int a = atlas_mesh->index_array[nface * 3];
+            int b = atlas_mesh->index_array[nface * 3 + 1];
+            int c = atlas_mesh->index_array[nface * 3 + 2];
+            *pindex++ = a;
+            *pindex++ = b;
+            *pindex++ = c;
+        }
+        fprintf(json, "%d", (int) faces.size());
+        if (++chart_iter != chart_to_faces.end()) {
+            fputc(',', json);
+        }
+    }
+    putc(']', json);
+    putc('\n', json);
+    fclose(json);
+    delete[] atlas_mesh->index_array;
+    atlas_mesh->index_array = indices;
+}
+
 void Thekla::atlas_dump(
     const Atlas_Output_Mesh * atlas_mesh,
     const Atlas_Input_Mesh * obj_mesh,

thekla/thekla/thekla_atlas.h

@@ -99,6 +99,8 @@ Atlas_Output_Mesh * atlas_generate(
     const Atlas_Options * options,
     Atlas_Error * error);
 
+void atlas_reorder_faces(Atlas_Output_Mesh * atlas_mesh, const char* outputfile);
+
 void atlas_dump(
     const Atlas_Output_Mesh * atlas_mesh,
     const Atlas_Input_Mesh * object_mesh,