AmbientCG Web API

[Josh]

AmbientCG has about 3000 PBR materials and a simple REST web API.

List categories:
https://ambientcg.com/api/v2/categories_json

List files in category:
https://ambientcg.com/api/v2/full_json?include=imageData,downloadData&category=PavingStones

These URLs can be loaded with FetchURL. There is a JSON parsing library included in the Scripts/System folder, dkjson.lua. This is used by the debugger. I have not used it myself for anything.

More docs here:
https://docs.ambientcg.com/api/v2/

[Josh]

Example:

local json = require 'System/dkjson'

local s = FetchUrl("https://ambientcg.com/api/v2/categories_json")

local t = json.decode(s)

if type(t) == "table" then
    local n
    for n = 1, #t do
        if (type(t[n]) == "table") then
            if type(t[n]["categoryName"]) == "string" then
                Print(t[n]["categoryName"])
            end
        end
    end
end

Download and extract:

DownloadFile("https://ambientcg.com/get?file=PavingStones137_1K-JPG.zip", GetPath(PATH_DESKTOP).."/test.zip" )
local pak = LoadPackage(GetPath(PATH_DESKTOP).."/test.zip")
if pak then
    local dir = pak:LoadDir("")
    local n
    for n = 1, #dir do
        if pak:FileType(dir[n]) == 1 then
            pak:ExtractFile(dir[n], GetPath(PATH_DESKTOP).."/"..dir[n])
        end
    end
    pak:Close()
end

 

[klepto2]

Hi, 

I have tried various JSON parsers for lua. And they are all slow as hell (at least if the json string is a larger one). In my API -Module for Polyhaven i have integrated a function which converts the nlohman:json object into a lua table and this is magnitudes faster than any lua json library. Also the usage is very easy and lua like.

void jsonToLua(const nlohmann::json& json, lua_State* L) {
    switch (json.type()) {
    case nlohmann::json::value_t::null:
        lua_pushnil(L);
        break;
    case nlohmann::json::value_t::boolean:
        lua_pushboolean(L, json.get<bool>());
        break;
    case nlohmann::json::value_t::number_integer:
        lua_pushinteger(L, json.get<int>());
        break;
    case nlohmann::json::value_t::number_unsigned:
        lua_pushinteger(L, json.get<unsigned>());
        break;
    case nlohmann::json::value_t::number_float:
        lua_pushnumber(L, json.get<double>());
        break;
    case nlohmann::json::value_t::string:
        lua_pushstring(L, json.get<std::string>().c_str());
        break;
    case nlohmann::json::value_t::array:
        lua_newtable(L);
        for (size_t i = 0; i < json.size(); ++i) {
            lua_pushinteger(L, i + 1); // Lua arrays are 1-indexed
            jsonToLua(json[i], L);
            lua_settable(L, -3);
        }
        break;
    case nlohmann::json::value_t::object:
        lua_newtable(L);
        for (auto it = json.begin(); it != json.end(); ++it) {
            lua_pushstring(L, it.key().c_str());
            jsonToLua(it.value(), L);
            lua_settable(L, -3);
        }
        break;
    default:
        // Handle other types if needed
        break;
    }
}

int lua_JsonToLua(lua_State* L)
{
    std::string jsonString;

    if (lua_isstring(L, -1))
    {
        jsonString = lua_tostring(L, -1);
    }

    auto json = nlohmann::json::parse(jsonString);
    jsonToLua(json, L);

    return 1;
}

extern "C"
{
    __declspec(dllexport) int luaopen_PolyHavenApiClient(lua_State* L) {
        // Load the DLL and create an instance of PolyHavenApiClient

        lua_newtable(L);
        int sz = lua_gettop(L);
        lua_pushcfunction(L, lua_JsonToLua);   lua_setfield(L, -2, "JsonToLua");

        lua_settop(L, sz);

        return 1;
    }
}

With this you can do something like this:

local assets = extension.api.getAssets(type,cat) --just a sample api call i use to retrieve the json data
local assetTable = extension.json.JsonToLua(assets) -- convert json string to lua table

Print(assetTable.bark_brown_01.name)

--or iterating sorted by keys

function pairsByKeys (t, f)
    local a = {}
    for n in pairs(t) do table.insert(a, n) end
    table.sort(a, f)
    local i = 0      -- iterator variable
    local iter = function ()   -- iterator function
      i = i + 1
      if a[i] == nil then return nil
      else return a[i], t[a[i]]
      end
    end
    return iter
end

for key,data in pairsByKeys(extension.currentAssets ) do
  Print(key.." Displayname: "..data.name)
  --Prints in this case eg: "bark_brown_01 Displayname: Bark Brown 01
end
  

 

[Josh]

Updated example that uses LoadTable() instead of the Lua JSON parser:

local s = FetchUrl("https://ambientcg.com/api/v2/categories_json")

local t = LoadTable(s)

if type(t) == "table" then
    local n
    for n = 1, #t do
        if (type(t[n]) == "table") then
            if type(t[n]["categoryName"]) == "string" then
                Print(t[n]["categoryName"])
            end
        end
    end
end

 

[Josh]

The Lua debugger is actually using Lua socket, not libcurl. A couple of things to note:

• Curl (curl.exe) is now included standard on WIndows 10 and 11.
• Having libcurl.dll in the application's root directory will cause the Steam build to crash, presumably because the Steamworks API is using a different version of the DLL: https://steamcommunity.com/groups/steamworks/discussions/0/6699728899096777474/