How to import 3D model file from memory as a file stream to assimp importer?

OpenGL OpenGL: Advanced Coding
1

Hello

if you have seen before, this is the how most of tutorials use the assimp lib to import a 3D model into the opengl context .

const aiScene* scene = importer.ReadFile(fileName, aiProcess_Triangulate | aiProcess_FlipUVs | aiProcess_GenSmoothNormals | aiProcess_JoinIdenticalVertices);

The ReadFile method accept a reference to the physical memory of the file .

const std::string& fileName

my question is how can i use the other method provided by assimp called :
ReadFilefrommemory .

is it possible to use this method to accept a filearray as input ?

thanks

2

Assimp::Importer::ReadFileFromMemory requires a pointer to the data. The data can be a char[], std::string, std::vector<uint8_t> or similar. Anything that holds raw data in contiguous memory and can provide a pointer to it (I have no idea what a “filearray” is). The pHint parameter should be the file extension; without this the library will have to deduce the format from the data, which typically requires that the format starts with some kind of signature.

3

thanks for your reply
by any chance is there any example that i can follow ?
any kind of code snippet

5

How can i define the size of the data coming to this method ?

   const aiScene* ReadFileFromMemory(
        const void* pBuffer,
        size_t pLength,
        unsigned int pFlags,
        const char* pHint = "");

as an example , what can be the correct input for pbuffer and pLength ?

it gives me the following error :

Model (my_file) failed get loaded: File is too small

Thanks

6

Reading from memory is for when you have already loaded some file directly into memory and you want the library to parse and understand it. The “correct input” would be a pointer to where that data starts and the number of bytes in it.

7

you are write .

i’m trying to write a simple c++ block of code , to import the file into a buffer and then pass the buffer to this method .
but i have difficulty to understand how to manage the c++ code .
can you provide me with some example or at least where i should look for an answer ?

for example i don’t understand the meaning of this error coming from assimp loader

Model (my_file) failed get loaded: File is too small

tnx

8

I don’t understand it either, because you didn’t provide the code/data that generated it. Without knowing what you did, the error message is without meaning.

Try posting the code you’re using.

9 
	std::ifstream file("Models/test.stl", std::ios::binary | std::ios::ate);

	if (!file.is_open()) 
	{
		std::cout << "file did not get open" << std::endl;
	}
	size_t fileSize = file.tellg();
	file.seekg(0);
	char* pBuffer = new char[fileSize];
	file.read(pBuffer, fileSize);

	file.close();

	// After everything is done.
	delete[] pBuffer;
10

and then i pass pBuffer and fileSize as the first 2 arguments of the ReadFileFromMemory

11

I have found the answer

put this function in your project’s main file:
project_name.cpp

string readFile(const string& fileName)
 {
     	ifstream ifs(fileName.c_str(), ios::in | ios::binary | ios::ate);

    	ifstream::pos_type fileSize = ifs.tellg();
    	ifs.seekg(0, ios::beg);

    	vector<char> bytes(fileSize);
    	ifs.read(bytes.data(), fileSize);

    	return string(bytes.data(), fileSize);
    }

in the same file , inside the main function make an object of the readFile function and give the model file as input to it
put the data and length of the buffer in 2 variables

 std::string my_file = readFile2("models/model_file.EXTENTION");
   const char* pbuffer = my_file.data();
    size_t  plenght =  my_file.length();

send these 2 variable as input into the LoadModel function as following

 void Model::LoadModel(const void* pbuffer, size_t plenght )
    {
    	Assimp::Importer importer;
    	const aiScene* scene = importer.ReadFileFromMemory(pbuffer, plenght , aiProcess_Triangulate | aiProcess_FlipUVs | aiProcess_GenSmoothNormals | aiProcess_JoinIdenticalVertices,"EXTENTION");

    	// use the read error mechanism 

    	if (!scene)
    	{
    		printf("Model (%s) failed get loaded: %s", "my_file" , importer.GetErrorString());
    		return;
    	}

    	LoadNode(scene->mRootNode, scene);

    	LoadMaterials(scene);
    }