how to use multiple vbos

OpenGL OpenGL: Basic Coding
1

Hello, i’m new to OpenGL and i wanted to draw multiple objects. (VC++)
i use opengl 3.3 and all tutorials and code found online is deprecated.
how can i draw multiple objects? need i to use multiple vbos or multiple vaos?
and how can i do it?
sorry for my english, it’s not my native language;
p.s. i’ve put my code as attachment.[ATTACH]947[/ATTACH]

2

Depends largely on your project, but if you’re going to draw two very different looking objects, say a cube and a plane, then using two different vaos is a good idea.

What you need to do is bind a vao (say vao_cube), then bind the cube vbo and everything. Once done, you bind the other vao (vao_plane), an bind ITS plane vbo.

Now when drawing, you bind a vao and draw, bind the next vao and draw that. The vao stores the vbo and vertex attributes and stuff in it. So everytime you bind a vao, think of it as setting some drawing settings before doing the draw.

3

[QUOTE=Velator;1265004]Depends largely on your project, but if you’re going to draw two very different looking objects, say a cube and a plane, then using two different vaos is a good idea.

What you need to do is bind a vao (say vao_cube), then bind the cube vbo and everything. Once done, you bind the other vao (vao_plane), an bind ITS plane vbo.

Now when drawing, you bind a vao and draw, bind the next vao and draw that. The vao stores the vbo and vertex attributes and stuff in it. So everytime you bind a vao, think of it as setting some drawing settings before doing the draw.[/QUOTE]

thanks but can you say me what i do wrong in my code?
i can’t get it to work![ATTACH]950[/ATTACH]

4

Well, I can’t really go through all of that right now. But I noticed you used glBindVertexArray(vao) twice, even though you only have one vao. And I don’t see the vertex array for the floor.

What you need to do is something like this:


glGenVertexArrays(1, &vaoCube);
glGenVertexArrays(1, &vaoPlane);
glGenBuffers(1, &vboCube);
glGenBuffers(1, &vboPlane);

//here we set things up for the cube vao
//the vao will store the vbo with it and every time you bind it and call glDrawArrays, it will use the vbo associated with the bound vao.
glBindVertexArray(vaoCube);

glBindBuffer(GL_ARRAY_BUFFER, vboCube);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices_Cube), vertices_Cube, GL_STATIC_DRAW); //using the vertices_Cube vertex array

//shader vertex attribs and stuff here


//now settings things up for the plane vao
glBindVertexArray(vaoPlane);

glBindBuffer(GL_ARRAY_BUFFER, vboPlane);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices_plane), vertices_plane, GL_STATIC_DRAW); //using the vertices_plane vertex array

//shader vertex attribs and stuff here


//NOW when you want to draw the cube and the plane, you bind its vao first

while(drawloo)
{
//clear and stuff

glBindVertexArray(vaoCube); //bind the cube vao
glDrawArrays(...); //will use vboCube

glBindVertexArray(vaoPlane); //bind the cube vao
glDrawArrays(...);//will use vboPlane

//other stuff
}
5

i need to create a shader for every vao???
p.s. it still don’t display the second vao.

here my modified code:
init:


// Create Vertex Array Object
	glGenVertexArrays(1, &vao);
	glGenVertexArrays(1, &vao2);

	// Create a Vertex Buffer Object and copy the vertex data to it
	glGenBuffers(1, &vbo);
	glGenBuffers(1, &vbo2);

	glBindVertexArray(vao);

	GLfloat vertices[] = { ..... };
        
        glBindBuffer(GL_ARRAY_BUFFER, vbo);
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

        glBindVertexArray(vao);


	GLfloat vertices2[] = { ......};
        
	glBindBuffer(GL_ARRAY_BUFFER, vbo2);
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices2), vertices2, GL_STATIC_DRAW);

loop:


                // Draw cube
		glBindVertexArray(vao);
		glDrawArrays(GL_TRIANGLES, 0, 36);

		glBindVertexArray(vao2);
		glDrawArrays(GL_TRIANGLES, 0, 6);
6

[QUOTE=snowyCoder;1265024]i need to create a shader for every vao???
[/QUOTE]

No you can use the same shader to perform multiple draw calls for data in different VAOs

7

so why it doesn’t work?

8

In the setup part of your code you bind “vao” twice: glBindVertexArray(vao) instead of “vao2”.

9

fixed it but still does not work :frowning:
it doesn’t buffer the first vertices

10

Well, nobody knows the code and shaders you are using now. Difficult to help that way, maybe post all relevant parts of the code.
I don’t see that you enabled attributes for both Vaos. Did you actually call glVertexAttribPointer and glEnableVertexAttribArray?

11

[QUOTE=Betrayal;1265030]Well, nobody knows the code and shaders you are using now. Difficult to help that way, maybe post all relevant parts of the code.
I don’t see that you enabled attributes for both Vaos. Did you actually call glVertexAttribPointer and glEnableVertexAttribArray?[/QUOTE]

i used glVertexAttribPointer on uniforms, but i don’t know what glEnableVertexAttribArray does.
anyway this ([ATTACH]953[/ATTACH]) is my full code,
the things in game loop are for rotating objects, don’t care about that.
thanks to everyone is answering, you’re really helping me a lot!