Parse 'Tf' field in MTL.

experimental/tinyobj_loader_opt.h

@@ -764,7 +764,8 @@ static void LoadMtl(std::map<std::string, int> *material_map,
     }
 
     // transmittance
-    if (token[0] == 'K' && token[1] == 't' && IS_SPACE((token[2]))) {
+    if ((token[0] == 'K' && token[1] == 't' && IS_SPACE((token[2]))) ||
+        (token[0] == 'T' && token[1] == 'f' && IS_SPACE((token[2])))) {
       token += 2;
       float r, g, b;
       parseFloat3(&r, &g, &b, &token);

models/issue-95.mtl

@@ -0,0 +1,5 @@
+newmtl default
+Ka 0 0 0
+Kd 0 0 0
+Ks 0 0 0
+Tf 0.1 0.2 0.3

models/issue-95.obj

@@ -0,0 +1,7 @@
+mtllib issue-92.mtl
+o Test
+v 1.864151 -1.219172 -5.532511
+v 0.575869 -0.666304 5.896140
+v 0.940448 1.000000 -1.971128
+usemtl default
+f 1 2 3

tests/tester.cc

@@ -367,6 +367,24 @@ TEST_CASE("trailing_whitespace_in_mtl", "[Issue92]") {
   REQUIRE(0 == materials[0].diffuse_texname.compare("tmp.png"));
 }
 
+TEST_CASE("transmittance_filter", "[Issue95]") {
+  tinyobj::attrib_t attrib;
+  std::vector<tinyobj::shape_t> shapes;
+  std::vector<tinyobj::material_t> materials;
+
+  std::string err;
+  bool ret = tinyobj::LoadObj(&attrib, &shapes, &materials, &err, "../models/issue-95.obj", gMtlBasePath);
+
+  if (!err.empty()) {
+    std::cerr << err << std::endl;
+  }
+  REQUIRE(true == ret);
+  REQUIRE(1 == materials.size());
+  REQUIRE(0.1 == Approx(materials[0].transmittance[0]));
+  REQUIRE(0.2 == Approx(materials[0].transmittance[1]));
+  REQUIRE(0.3 == Approx(materials[0].transmittance[2]));
+}
+
 #if 0
 int
 main(