OpenGL compute shaders: How do I bind an ssbo for output?

OpenGL
1

I have been looking everywhere and there isn’t anything that clearly says how to do this. I have found things for input buffers, for read write buffers, but nothing useful about output buffers. I think that I know how to get the data back. I need clear instructions and so far I haven’t found any.

void ModelBind::load(vector<nessVertex> vertices)
{
	this->vertices = vertices;	
}

void ModelBind::bind()
{
	if (first) {

		//this is the starting stuff so I guess it doesn't have to be done again

		//this is my input ssbo
		glGenBuffers(1, &buffer);
		glBindBuffer(GL_SHADER_STORAGE_BUFFER, buffer);  
		glBufferData(GL_SHADER_STORAGE_BUFFER, vertices.size() * sizeof(nessVertex), &vertices[0], GL_STATIC_DRAW);		// Bind to binding point 0 for SSBO
		glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 0, buffer);
		glBindBuffer(GL_SHADER_STORAGE_BUFFER, 0);

		//this is supposed to be my output ssbo
		glGenBuffers(1, &outputBuffer);
		glBindBuffer(GL_SHADER_STORAGE_BUFFER, outputBuffer);
		glBufferData(GL_SHADER_STORAGE_BUFFER, vertices.size() * sizeof(glm::vec3), nullptr, GL_DYNAMIC_DRAW);
		glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 1, outputBuffer);
		outData.resize(vertices.size());
		first = false;
	}
	else {
		//Dynamic write
		//glBindBuffer(GL_SHADER_STORAGE_BUFFER, buffer);
		//glBufferSubData(GL_SHADER_STORAGE_BUFFER, 0, vertices.size() * sizeof(nessVertex), vertices.data());

		// so this is just to bind the buffers because the input should be in memory right?
		glBindBuffer(GL_SHADER_STORAGE_BUFFER, buffer);

		glBindBuffer(GL_SHADER_STORAGE_BUFFER, outputBuffer);
		//glBufferData(GL_SHADER_STORAGE_BUFFER, vertices.size() * sizeof(glm::vec3), nullptr, GL_STREAM_COPY);	
		
	}
}

void ModelBind::retreive()
{
	glBindBuffer(GL_SHADER_STORAGE_BUFFER, outputBuffer);
	GLvoid* p = glMapBuffer(GL_SHADER_STORAGE_BUFFER, GL_WRITE_ONLY);
	
	memcpy(p, &outData[0], vertices.size() * sizeof(glm::vec3));
	glUnmapBuffer(GL_SHADER_STORAGE_BUFFER);
	
}
2

You need to use glBindBufferBase and/or glBindBufferRange with a target of GL_SHADER_STORAGE_BUFFER to bind to a specific binding point.

You can set the binding point of a buffer variable in the shader using a layout(binding=...) qualifier, or in the client after the program has been linked using glShaderStorageBlockBinding.