OpenGL first person camera rotation and translation

Question

I'm trying to write a simple maze game, without using any deprecated OpenGL API (i.e. no immediate mode). I'm using one Vertex Buffer Object for each tile I have in my maze, which is essentially a combination of four Vertexs:

class Vertex {
public:
    GLfloat x, y, z; // coords
    GLfloat tx, ty;  // texture coords

    Vertex();
};

and are stored in VBOs like this:

void initVBO()
{
    Vertex vertices[4];
    vertices[0].x = -0.5;
    vertices[0].y = -0.5;
    vertices[0].z = 0.0;
    vertices[0].tx = 0.0;
    vertices[0].ty = 1.0;
    vertices[1].x = -0.5;
    vertices[1].y = 0.5;
    vertices[1].z = 0.0;
    vertices[1].tx = 0.0;
    vertices[1].ty = 0.0;
    vertices[2].x = 0.5;
    vertices[2].y = 0.5;
    vertices[2].z = 0.0;
    vertices[2].tx = 1.0;
    vertices[2].ty = 0.0;
    vertices[3].x = 0.5;
    vertices[3].y = -0.5;
    vertices[3].z = 0.0;
    vertices[3].tx = 1.0;
    vertices[3].ty = 1.0;

    glGenBuffers(1, &vbo);
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(Vertex)*4, &vertices[0].x, GL_STATIC_DRAW);

    ushort indices[4];
    indices[0] = 0;
    indices[1] = 1;
    indices[2] = 2;
    indices[3] = 3;

    glGenBuffers(1, &ibo);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(ushort) * 4, indices, GL_STATIC_DRAW);
}

Now, I'm stuck on the camera movement. In a previous version of my project, I used glRotatef and glTranslatef to translate and rotate the scene and then I rendered every tile using glBegin()/glEnd() mode. But these two functions are now deprecated, and I didn't find any tutorial about creating a camera in a context using only VBOs. Which is the correct way to proceed? Should I loop between every tile modifying the position of the vertices according to the new camera position?

Are you using the fixed-function pipeline? Also, there is no concept of a camera in OpenGL. You multiply each vertex with a model-view-projection matrix (where the view matrix is the one you are interested in). You do that in your vertex shader (you can also use the matrix stack if you are allowed to use the fixed function pipeline). And this question may be better suited for gamedev.stackexchange.com — Samaursa
@Samaursa As I said, I'm not using the fixed-function pipeline, because from what I've read, it is deprecated. In my render method, I basically bind my VBOs and use the glDrawElements() method to render them. Besides, also the glPopMatrix() and glPushMatrix() methods are deprecated, so I don't really know where to start from. — Pietro Lorefice
See my answer (updated with several edits - apologize for that, I forgot to add one of the sections) — Samaursa
"I'm using one Vertex Buffer Object for each tile I have in my maze" Stop doing that. You shouldn't make tiny buffer objects like that. Put all the tiles in one buffer. — Nicol Bolas

datenwolf datenwolf · Accepted Answer · 2012-01-22T18:09:51

But these two functions are now deprecated, and I didn't find any tutorial about creating a camera in a context using only VBOs.

VBOs have nothing to do with this.

Immediate mode and the matrix stack are two different pairs of shoes. VBOs deal with getting geometry data to the renderer, the matrix stack deals with getting the transformation there. It's only geometry data that's affected by VBOs.

As for your question: You calculate the matrices yourself and pass them to the shader by uniform. It's also important to understand the OpenGL's matrix function never have been GPU accelerated (except for one single machine, SGI's Onyx), so this didn't even offer some performance gain. Actually using OpenGL's matrix stack had a negative impact on overall performance, due to carrying out redundant operations, that have to be done somewhere else in the program as well.

For a simple matrix math library look at my linmath.h http://github.com/datenwolf/linmath.h

OpenGL first person camera rotation and translation

3 Answers