diff --git a/luprex/cpp/core/animqueue.cpp b/luprex/cpp/core/animqueue.cpp
index 15ecb585..55527692 100644
--- a/luprex/cpp/core/animqueue.cpp
+++ b/luprex/cpp/core/animqueue.cpp
@@ -55,19 +55,31 @@ static void parse_value(std::string_view vstr, AnimValue *v) {
 
 static AnimValue parse_anim_value(LuaCoreStack &LS, LuaSlot val, LuaSlot tmp) {
     AnimValue result;
-    if (LS.isboolean(val)) {
-        result.set_boolean(LS.ckboolean(val));
-    } else if (LS.isnumber(val)) {
-        result.set_number(LS.cknumber(val));
-    } else if (LS.isstring(val)) {
-        result.set_string(LS.ckstring(val));
-    } else if (LS.isxyz(val)) {
-        result.set_dxyz(LS.ckxyz(val));
-    } else if (LS.rawequal(val, LuaToken("auto"))) {
-        result.set_auto();
-    } else {
-        result.set_uninitialized();
+    auto tboolean = LS.tryboolean(val);
+    if (tboolean) {
+        result.set_boolean(*tboolean);
+        return result;
     }
+    auto tnumber = LS.trynumber(val);
+    if (tnumber) {
+        result.set_number(*tnumber);
+        return result;
+    }
+    auto tstring = LS.trystringview(val);
+    if (tstring) {
+        result.set_string(*tstring);
+        return result;
+    }
+    auto txyz = LS.tryxyz(val);
+    if (txyz) {
+        result.set_dxyz(*txyz);
+        return result;
+    }
+    if (LS.rawequal(val, LuaToken("auto"))) {
+        result.set_auto();
+        return result;
+    }
+    result.set_uninitialized();
     return result;
 }
 
diff --git a/luprex/cpp/core/luastack.cpp b/luprex/cpp/core/luastack.cpp
index b6a7e22b..f50a3338 100644
--- a/luprex/cpp/core/luastack.cpp
+++ b/luprex/cpp/core/luastack.cpp
@@ -96,95 +96,73 @@ void LuaCoreStack::argerr(const char *nm, const char *tp) const {
     luaL_error(L_, "'%s' should be %s", nm, tp);
 }
 
-bool LuaCoreStack::isinteger(LuaSlot s) const {
-    if (lua_type(L_, s) == LUA_TNUMBER) {
-        lua_Number result = lua_tonumber(L_, s);
-        if (lua_Integer(result) == result) return true;
+std::optional<bool> LuaCoreStack::tryboolean(LuaSlot s) const {
+    if (lua_type(L_, s) == LUA_TBOOLEAN) {
+        return lua_toboolean(L_, s);
     }
-    return false;
+    return std::nullopt;
 }
 
-bool LuaCoreStack::isint(LuaSlot s) const {
+std::optional<lua_Integer> LuaCoreStack::tryinteger(LuaSlot s) const {
     if (lua_type(L_, s) == LUA_TNUMBER) {
         lua_Number result = lua_tonumber(L_, s);
-        if (int(result) == result) return true;
-    }
-    return false;
-}
-
-bool LuaCoreStack::isxyz(LuaSlot s) const {
-    if (lua_istable(L_, s) && (lua_nkeys(L_, s) == 3)) {
-        int top = lua_gettop(L_);
-        lua_rawgeti(L_, s, 3);
-        lua_rawgeti(L_, s, 2);
-        lua_rawgeti(L_, s, 1);
-        if (lua_isnumber(L_, -1) && lua_isnumber(L_, -2) && lua_isnumber(L_, -3)) {
-            lua_settop(L_, top);
-            return true;
+        if (lua_Integer(result) == result) {
+            return lua_Integer(result);
         }
-        lua_settop(L_, top);
     }
-    return false;
+    return std::nullopt;
 }
 
-bool LuaCoreStack::ckboolean(LuaSlot s) const {
-    checkboolean(s, "value");
-    return lua_toboolean(L_, s) ? true:false;
-}
-
-lua_Integer LuaCoreStack::ckinteger(LuaSlot s) const {
-    checknumber(s, "value");
-    luaL_checktype(L_, s, LUA_TNUMBER);
-    lua_Number result = lua_tonumber(L_, s);
-    lua_Integer iresult(result);
-    if (iresult != result) {
-        luaL_error(L_, "not a valid integer");
-        return 0;
+std::optional<int> LuaCoreStack::tryint(LuaSlot s) const {
+    if (lua_type(L_, s) == LUA_TNUMBER) {
+        lua_Number result = lua_tonumber(L_, s);
+        if (int(result) == result) {
+            return int(result);
+        }
     }
-    return iresult;
+    return std::nullopt;
 }
 
-int LuaCoreStack::ckint(LuaSlot s) const {
-    checknumber(s, "value");
-    lua_Number result = lua_tonumber(L_, s);
-    int iresult(result);
-    if (iresult != result) {
-        luaL_error(L_, "not a valid int");
-        return 0;
+std::optional<lua_Number> LuaCoreStack::trynumber(LuaSlot s) const {
+    if (lua_type(L_, s) == LUA_TNUMBER) {
+        return lua_tonumber(L_, s);
     }
-    return iresult;
+    return std::nullopt;
 }
 
-lua_Number LuaCoreStack::cknumber(LuaSlot s) const {
-    checknumber(s, "value");
-    return lua_tonumber(L_, s);
+std::optional<eng::string> LuaCoreStack::trystring(LuaSlot s) const {
+    if (lua_type(L_, s) == LUA_TSTRING) {
+        size_t len;
+        const char *str = lua_tolstring(L_, s, &len);
+        return eng::string(str, len);
+    }
+    return std::nullopt;
 }
 
-eng::string LuaCoreStack::ckstring(LuaSlot s) const {
-    checkstring(s, "value");
-    size_t len;
-    const char *str = lua_tolstring(L_, s, &len);
-    return eng::string(str, len);
+std::optional<std::string_view> LuaCoreStack::trystringview(LuaSlot s) const {
+    if (lua_type(L_, s) == LUA_TSTRING) {
+        size_t len;
+        const char *str = lua_tolstring(L_, s, &len);
+        return std::string_view(str, len);
+    }
+    return std::nullopt;
 }
 
-std::string_view LuaCoreStack::ckstringview(LuaSlot s) const {
-    checkstring(s, "value");
-    size_t len;
-    const char *str = lua_tolstring(L_, s, &len);
-    return std::string_view(str, len);
+std::optional<lua_State*> LuaCoreStack::trythread(LuaSlot s) const {
+    if (lua_type(L_, s) == LUA_TTHREAD) {
+        return lua_tothread(L_, s);
+    }
+    return std::nullopt;
 }
 
-lua_State *LuaCoreStack::ckthread(LuaSlot s) const {
-    checkthread(s, "value");
-    return lua_tothread(L_, s);
+std::optional<LuaToken> LuaCoreStack::trytoken(LuaSlot s) const {
+    if (lua_type(L_, s) == LUA_TLIGHTUSERDATA) {
+        return LuaToken(lua_touserdata(L_, s));
+    }
+    return std::nullopt;
 }
 
-LuaToken LuaCoreStack::cktoken(LuaSlot s) const {
-    checktoken(s, "value");
-    return LuaToken(lua_touserdata(L_, s));
-}
-
-util::DXYZ LuaCoreStack::ckxyz(LuaSlot s) const {
+std::optional<util::DXYZ> LuaCoreStack::tryxyz(LuaSlot s) const {
     if (lua_istable(L_, s) && (lua_nkeys(L_, s) == 3)) {
         int top = lua_gettop(L_);
         lua_rawgeti(L_, s, 3);
@@ -200,10 +178,106 @@ util::DXYZ LuaCoreStack::ckxyz(LuaSlot s) const {
         }
         lua_settop(L_, top);
     }
-    argerr("argument", "vector");
-    return util::DXYZ();
+    return std::nullopt;
 }
 
+bool LuaCoreStack::trytable(LuaSlot s) const {
+    return lua_istable(L_, s);
+}
+
+bool LuaCoreStack::trynil(LuaSlot s) const {
+    return lua_isnil(L_, s);
+}
+
+bool LuaCoreStack::tryfunction(LuaSlot s) const {
+    return lua_isfunction(L_, s);
+}
+
+bool LuaCoreStack::trycfunction(LuaSlot s) const {
+    return lua_iscfunction(L_, s);
+}
+
+bool LuaCoreStack::trytangible(LuaSlot s) const {
+    return (lua_istable(L_, s) && gettabletype(s) == LUA_TT_TANGIBLE);
+}
+
+
+
+bool LuaCoreStack::ckboolean(LuaSlot s, const char *argname) const {
+    auto result = tryboolean(s);
+    if (!result) argerr(argname, "boolean");
+    return *result;
+}
+
+lua_Integer LuaCoreStack::ckinteger(LuaSlot s, const char *argname) const {
+    auto result = tryinteger(s);
+    if (!result) argerr(argname, "integer");
+    return *result;
+}
+
+int LuaCoreStack::ckint(LuaSlot s, const char *argname) const {
+    auto result = tryint(s);
+    if (!result) argerr(argname, "int");
+    return *result;
+}
+
+lua_Number LuaCoreStack::cknumber(LuaSlot s, const char *argname) const {
+    auto result = trynumber(s);
+    if (!result) argerr(argname, "number");
+    return *result;
+}
+
+eng::string LuaCoreStack::ckstring(LuaSlot s, const char *argname) const {
+    auto result = trystring(s);
+    if (!result) argerr(argname, "string");
+    return *result;
+}
+
+std::string_view LuaCoreStack::ckstringview(LuaSlot s, const char *argname) const {
+    auto result = trystringview(s);
+    if (!result) argerr(argname, "string");
+    return *result;
+}
+
+lua_State * LuaCoreStack::ckthread(LuaSlot s, const char *argname) const {
+    auto result = trythread(s);
+    if (!result) argerr(argname, "thread");
+    return *result;
+}
+
+LuaToken LuaCoreStack::cktoken(LuaSlot s, const char *argname) const {
+    auto result = trytoken(s);
+    if (!result) argerr(argname, "token");
+    return *result;
+}
+
+util::DXYZ LuaCoreStack::ckxyz(LuaSlot s, const char *argname) const {
+    auto result = tryxyz(s);
+    if (!result) argerr(argname, "xyz");
+    return *result;
+}
+
+void LuaCoreStack::cktable(LuaSlot s, const char *argname) const {
+    if (!trytable(s)) argerr(argname, "table");
+}
+
+void LuaCoreStack::cknil(LuaSlot s, const char *argname) const {
+    if (!trynil(s)) argerr(argname, "nil");
+}
+
+void LuaCoreStack::ckfunction(LuaSlot s, const char *argname) const {
+    if (!tryfunction(s)) argerr(argname, "function");
+}
+
+void LuaCoreStack::ckcfunction(LuaSlot s, const char *argname) const {
+    if (!trycfunction(s)) argerr(argname, "c-function");
+}
+
+void LuaCoreStack::cktangible(LuaSlot s, const char *argname) const {
+    if (!trytangible(s)) argerr(argname, "tangible");
+}
+
+
 void LuaCoreStack::clearmetatable(LuaSlot tab) const {
     lua_pushnil(L_);
     lua_setmetatable(L_, tab);
diff --git a/luprex/cpp/core/luastack.hpp b/luprex/cpp/core/luastack.hpp
index 5cf11a4f..b2d0bd06 100644
--- a/luprex/cpp/core/luastack.hpp
+++ b/luprex/cpp/core/luastack.hpp
@@ -149,6 +149,7 @@
 #include <cstring>
 #include <type_traits>
 #include <cassert>
+#include <optional>
 
 #include "lua.h"
 #include "lauxlib.h"
@@ -354,7 +355,6 @@ private:
     }
 
     void argerr(const char *arg, const char *tp) const;
-
 public:
     LuaCoreStack(lua_State *L) : L_(L) {}
     
@@ -368,43 +368,69 @@ public:
 
     int type(LuaSlot s) const { return lua_type(L_, s); }
     void checktype(LuaSlot s, int type) const { luaL_checktype(L_, s, type); }
+    
+    // These functions try to turn a Lua value into a C++ value.
+    // If the lua value doesn't match the desired type, then these return
+    // false or an empty optional.  The ones that return bool only verify
+    // the value's type, they don't actually fetch the value.
+    
+    std::optional<bool>             tryboolean(LuaSlot s) const;
+    std::optional<lua_Integer>      tryinteger(LuaSlot s) const;
+    std::optional<int>              tryint(LuaSlot s) const;
+    std::optional<lua_Number>       trynumber(LuaSlot s) const;
+    std::optional<eng::string>      trystring(LuaSlot s) const;
+    std::optional<std::string_view> trystringview(LuaSlot s) const;
+    std::optional<lua_State*>       trythread(LuaSlot s) const;
+    std::optional<LuaToken>         trytoken(LuaSlot s) const;
+    std::optional<util::DXYZ>       tryxyz(LuaSlot s) const;
+    bool                            trytable(LuaSlot s) const;
+    bool                            trynil(LuaSlot s) const;
+    bool                            tryfunction(LuaSlot s) const;
+    bool                            trycfunction(LuaSlot s) const;
+    bool                            trytangible(LuaSlot s) const;
+    
+    // These functions turn a Lua value into a C++ value.
+    // If the lua value doesn't match the desired type,
+    // then these throw a lua error.  The argname is used
+    // for making a nice error message.
 
-    bool istable(LuaSlot s) const { return lua_type(L_, s) == LUA_TTABLE; }
-    bool isstring(LuaSlot s) const { return lua_type(L_, s) == LUA_TSTRING; }
-    bool isnumber(LuaSlot s) const { return lua_type(L_, s) == LUA_TNUMBER; }
-    bool isinteger(LuaSlot s) const;
-    bool isint(LuaSlot s) const;
-    bool isthread(LuaSlot s) const { return lua_type(L_, s) == LUA_TTHREAD; }
-    bool isfunction(LuaSlot s) const { return lua_type(L_, s) == LUA_TFUNCTION; }
-    bool iscfunction(LuaSlot s) const { return lua_iscfunction(L_, s) != 0; }
+    bool             ckboolean(LuaSlot s, const char *argname = "value") const;
+    lua_Integer      ckinteger(LuaSlot s, const char *argname = "value") const;
+    int              ckint(LuaSlot s, const char *argname = "value") const;
+    lua_Number       cknumber(LuaSlot s, const char *argname = "value") const;
+    eng::string      ckstring(LuaSlot s, const char *argname = "value") const;
+    std::string_view ckstringview(LuaSlot s, const char *argname = "value") const;
+    lua_State *      ckthread(LuaSlot s, const char *argname = "value") const;
+    LuaToken         cktoken(LuaSlot s, const char *argname = "value") const;
+    util::DXYZ       ckxyz(LuaSlot s, const char *argname = "value") const;
+    void             cktable(LuaSlot s, const char *argname = "value") const;
+    void             cknil(LuaSlot s, const char *argname = "value") const;
+    void             ckfunction(LuaSlot s, const char *argname = "value") const;
+    void             ckcfunction(LuaSlot s, const char *argname = "value") const;
+    void             cktangible(LuaSlot s, const char *argname = "value") const;
+    
+    // These functions check if a value can be converted
+    // to a C++ value.  They don't actually return the C++ value.
+    // It is more efficient to use the 'try' or 'ck' functions above if
+    // you also want the value itself.
+    
     bool isboolean(LuaSlot s) const { return lua_type(L_, s) == LUA_TBOOLEAN; }
-    bool isnil(LuaSlot s) const { return lua_type(L_, s) == LUA_TNIL; }
+    bool isinteger(LuaSlot s) const { return bool(tryinteger(s)); }
+    bool isint(LuaSlot s) const { return bool(tryint(s)); }
+    bool isnumber(LuaSlot s) const { return lua_type(L_, s) == LUA_TNUMBER; }
+    bool isstring(LuaSlot s) const { return lua_type(L_, s) == LUA_TSTRING; }
+    bool isstringview(LuaSlot s) const { return lua_type(L_, s) == LUA_TSTRING; }
+    bool isthread(LuaSlot s) const { return lua_type(L_, s) == LUA_TTHREAD; }
     bool istoken(LuaSlot s) const { return lua_islightuserdata(L_, s) != 0; }
-    bool isxyz(LuaSlot s) const;
+    bool isxyz(LuaSlot s) const { return bool(tryxyz(s)); }
+    bool istable(LuaSlot s) const { return lua_type(L_, s) == LUA_TTABLE; }
+    bool isnil(LuaSlot s) const { return lua_type(L_, s) == LUA_TNIL; }
+    bool isfunction(LuaSlot s) const { return lua_isfunction(L_, s); }
+    bool iscfunction(LuaSlot s) const { return lua_iscfunction(L_, s) != 0; }
+    bool istangible(LuaSlot s) const { return trytangible(s); }
+
+
 
-    void checktable(LuaSlot s, const char *n) const { if (!istable(s)) argerr(n, "table"); }
-    void checkstring(LuaSlot s, const char *n) const { if (!isstring(s)) argerr(n, "string"); }
-    void checknumber(LuaSlot s, const char *n) const { if (!isnumber(s)) argerr(n, "number"); }
-    void checkinteger(LuaSlot s, const char *n) const { if (!isinteger(s)) argerr(n, "integer"); }
-    void checkint(LuaSlot s, const char *n) const { if (!isint(s)) argerr(n, "int"); }
-    void checkthread(LuaSlot s, const char *n) const { if (!isthread(s)) argerr(n, "thread"); }
-    void checkfunction(LuaSlot s, const char *n) const { if (!isfunction(s)) argerr(n, "function"); }
-    void checkcfunction(LuaSlot s, const char *n) const { if (!iscfunction(s)) argerr(n, "cfunction"); }
-    void checkboolean(LuaSlot s, const char *n) const { if (!isboolean(s)) argerr(n, "boolean"); }
-    void checknil(LuaSlot s, const char *n) const { if (!isnil(s)) argerr(n, "nil"); }
-    void checktoken(LuaSlot s, const char *n) const { if (!istoken(s)) argerr(n, "token"); }
-    void checkxyz(LuaSlot s, const char *n) const { if (!isxyz(s)) argerr(n, "xyz"); }
-    
-    bool ckboolean(LuaSlot s) const;
-    lua_Integer ckinteger(LuaSlot s) const;
-    int ckint(LuaSlot s) const;
-    lua_Number cknumber(LuaSlot s) const;
-    eng::string ckstring(LuaSlot s) const;
-    std::string_view ckstringview(LuaSlot s) const;
-    lua_State *ckthread(LuaSlot s) const;
-    LuaToken cktoken(LuaSlot s) const;
-    util::DXYZ ckxyz(LuaSlot s) const;
-    
     void clearmetatable(LuaSlot tab) const;
     void setmetatable(LuaSlot tab, LuaSlot mt) const;
     bool getmetatable(LuaSlot mt, LuaSlot tab) const;
diff --git a/luprex/cpp/core/planemap.cpp b/luprex/cpp/core/planemap.cpp
index e9a6dcce..fb6ebb46 100644
--- a/luprex/cpp/core/planemap.cpp
+++ b/luprex/cpp/core/planemap.cpp
@@ -835,34 +835,35 @@ void PlaneScan::configure(LuaKeywordParser &kp) {
     bool have_near = false;
 
     if (kp.parse(val, "plane")) {
-        LS.checkstring(val, "plane");
-        plane_ = LS.ckstring(val);
+        plane_ = LS.ckstring(val, "plane");
         have_plane = true;
     }
 
     if (kp.parse(val, "center")) {
-        LS.checkxyz(val, "center");
-        util::DXYZ xyz = LS.ckxyz(val);
+        util::DXYZ xyz = LS.ckxyz(val, "center");
         center_ = xyz;
         have_center = true;
     }
 
     if (kp.parse(val, "radius")) {
-        if (LS.isnumber(val)) {
-            radius_.x = LS.cknumber(val);
-            radius_.y = radius_.z = radius_.x;
+        auto simple = LS.trynumber(val);
+        if (simple) {
+            radius_ = *simple;
             have_radius = true;
         } else {
-            LS.checkxyz(val, "radius");
-            util::DXYZ xyz = LS.ckxyz(val);
-            radius_ = xyz;
-            have_radius = true;
+            auto full = LS.tryxyz(val);
+            if (full) {
+                radius_ = *full;
+                have_radius = true;
+            }
+        }
+        if (!have_radius) {
+            luaL_error(L, "scan configuration: 'radius' must be a vector or number");
         }
     }
 
     if (kp.parse(val, "shape")) {
-        LS.checkstring(val, "shape");
-        eng::string shape = LS.ckstring(val);
+        eng::string shape = LS.ckstring(val, "shape");
         if (shape == "box") {
             shape_ = BOX;
         } else if (shape == "sphere") {
@@ -893,19 +894,17 @@ void PlaneScan::configure(LuaKeywordParser &kp) {
     }
 
     if (kp.parse(val, "include")) {
-        LS.checkboolean(val, "include");
         if (!have_near) {
             luaL_error(L, "scan configuration: 'include' specified without 'near'");
         }
-        include_near_ = LS.ckboolean(val);
+        include_near_ = LS.ckboolean(val, "include");
     }
 
     if (kp.parse(val, "wholeplane")) {
-        LS.checkstring(val, "wholeplane");
         if (have_plane || have_center || have_radius || have_shape) {
             luaL_error(L, "scan configuration: do not specify plane, center, shape, or radius with 'wholeplane'");
         }
-        plane_ = LS.ckstring(val);
+        plane_ = LS.ckstring(val, "wholeplane");
         set_whole_plane();
         have_plane = true;
         have_center = true;
diff --git a/luprex/cpp/core/table.cpp b/luprex/cpp/core/table.cpp
index cb5f9d19..e162c1f6 100644
--- a/luprex/cpp/core/table.cpp
+++ b/luprex/cpp/core/table.cpp
@@ -8,7 +8,7 @@
 // Does not thoroughly verify the vector.  Returns the size
 // of the vector.
 static int check_vector_quick(LuaCoreStack &LS, LuaSlot vector, LuaSlot tmp) {
-    LS.checktable(vector, "vector");
+    LS.cktable(vector, "vector");
     int nkeys = LS.nkeys(vector);
     if (nkeys > 0) {
         LS.rawget(tmp, vector, nkeys);
@@ -26,8 +26,8 @@ static int check_vector_quick(LuaCoreStack &LS, LuaSlot vector, LuaSlot tmp) {
 bool table_equal(LuaCoreStack &LS, LuaSlot t1, LuaSlot t2) {
     lua_State *L = LS.state();
     int top = lua_gettop(L);
-    LS.checktable(t1, "table1");
-    LS.checktable(t2, "table2");
+    LS.cktable(t1, "table1");
+    LS.cktable(t2, "table2");
     int nkeys1 = lua_nkeys(L, t1.index());
     int nkeys2 = lua_nkeys(L, t2.index());
     if (nkeys1 != nkeys2) return false;
@@ -262,7 +262,7 @@ LuaDefine(table_clear, "table,metaflag",
     LuaArg tab, clearmeta;
     LuaVar metatable, metafield;
     LuaDefStack LS(L, tab, clearmeta, metatable, metafield);
-    LS.checktable(tab, "table");
+    LS.cktable(tab, "table");
     if (LS.ckboolean(clearmeta)) {
         LS.getmetatable(metatable, tab);
         if (LS.istable(metatable)) {
@@ -557,9 +557,11 @@ LuaDefine(deque_size, "deque", "return the number of items in the deque") {
     LuaArg deque;
     LuaRet size;
     LuaDefStack LS(L, deque, size);
-    LS.checktable(deque, "deque");
+    LS.cktable(deque, "deque");
     LS.rawget(size, deque, DEQUE_FILL);
-    LS.checknumber(size, "deque size");
+    if (!LS.tryinteger(size)) {
+        luaL_error(L, "deque has been corrupted");
+    }
     return LS.result();
 }
 
diff --git a/luprex/cpp/core/world-accessor.cpp b/luprex/cpp/core/world-accessor.cpp
index 238a2caf..cc7cf082 100644
--- a/luprex/cpp/core/world-accessor.cpp
+++ b/luprex/cpp/core/world-accessor.cpp
@@ -444,7 +444,7 @@ LuaDefine(tangible_find, "config",
     "|circular area."
     "|"
     "|It is also valid to use math.huge (infinity) as a radius.  For"
-    "|example, you could use shape='cylinder' and radiusz=math.huge"
+    "|example, you could use shape='cylinder' and radius.z=math.huge"
     "|to scan an infinitely tall cylinder."
     "|"
     "|If you are making a 2D game, it works fine to set all object Z"
diff --git a/luprex/cpp/core/world-difftab.cpp b/luprex/cpp/core/world-difftab.cpp
index b571b717..ae9e29ae 100644
--- a/luprex/cpp/core/world-difftab.cpp
+++ b/luprex/cpp/core/world-difftab.cpp
@@ -447,10 +447,10 @@ LuaDefine(table_diffcompare, "mtnmap,mtab,stnmap,stab", "for unit testing only")
     LuaVar tthread;
     LuaDefStack MLS(L, mtnmap, mtab, mstnmap, mstab, dbgstring, tthread);
     // Check the arguments.
-    MLS.checktable(mtnmap, "mtnmap");
-    MLS.checktable(mstnmap, "mstnmap");
-    MLS.checktable(mtab, "mtab");
-    MLS.checktable(mstab, "mstab");
+    MLS.cktable(mtnmap, "mtnmap");
+    MLS.cktable(mstnmap, "mstnmap");
+    MLS.cktable(mtab, "mtab");
+    MLS.cktable(mstab, "mstab");
 
     // Create a temporary thread to be the 'synch model'.  We'll use the
     // existing thread as the 'master model'.  Move two tables to the synch thread.
@@ -477,9 +477,9 @@ LuaDefine(table_diffapply, "mtnmap,mtab,mstab", "for unit testing only") {
     LuaVar tthread, tangibles, mntmap, key, val;
     LuaDefStack MLS(L, mtnmap, mtab, mstab, eql, eqlstr, rtab, tthread, tangibles, mntmap, key, val);
     // Check the arguments.
-    MLS.checktable(mtnmap, "mtnmap");
-    MLS.checktable(mtab, "mtab");
-    MLS.checktable(mstab, "mstab");
+    MLS.cktable(mtnmap, "mtnmap");
+    MLS.cktable(mtab, "mtab");
+    MLS.cktable(mstab, "mstab");
 
     // Get the tangibles map.
     MLS.rawget(tangibles, LuaRegistry, "tangibles");
diff --git a/luprex/lua/uglyglobals.lua b/luprex/lua/uglyglobals.lua
index 5ff8c19d..94e408eb 100644
--- a/luprex/lua/uglyglobals.lua
+++ b/luprex/lua/uglyglobals.lua
@@ -1,10 +1,10 @@
 makeclass('ug')
 
 function ug.the()
-  return tangible.scan('globals',0,0,0,true)[1]
+  return tangible.find{plane="globals", center={0,0,0}, radius=1}[1]
   end
 
-lis=tangible.scan('globals',0,0,0,true)
+lis=tangible.find{plane="globals", center={0,0,0}, radius=1}
 if #lis==0 then
   local ugid=tangible.build{class='ug', animstate={xyz={0,0,0}, plane='globals'}}
   print("The global table is "..tangible.id(ugid))
@@ -42,8 +42,8 @@ function tabcat(t1,t2)
 
 -- Example: multistart(function(t) return tangible.id(t)%3==0 end,function() print("Tangible "..tangible.id(tangible.place()).." here") end)
 function multistart(fil,closure)
-  local lis=tangible.scan('nowhere',0,0,100,false)
-  tabcat(lis,tangible.scan('main',0,0,100,true))
+  local lis=tangible.find{plane="nowhere", center={0,0,100}, radius=1}
+  tabcat(lis,tangible.find{plane="main", center={0,0,100}, radius=1})
   local filter=type(fil)=='function' and fil or function(t) return isa(t,fil) end
   for _,t in ipairs(lis) do if filter(t) then tangible.start(t,closure) end end
   end