How do I render a matrix as a cube in OpenGL?

Question

I am trying to create a rubiks cube using openGL. Within the code for each individual piece, I want to draw a cube around x, y, z using a matrix. I am wondering how do I draw my cube once I have processed it using glMultMatrix? Thanks!

class Piece:

    def __init__(self, x, y, z, position):
        self.x = x
        self.y = y
        self.z = z
        self.matrix = position

    def draw(self, axis, slice, dir):

        glPushMatrix()

        glMultMatrixf(self.matrix)

        glBegin(GL_QUADS)

        #
        # What would go here to draw a cube based off of self.matrix?
        # 

        glEnd()

        glPopMatrix()

score 1 · Answer 1 · edited Apr 04 '20 at 19:14

You just render axis aligned cube centered by (0,0,0) so set of 4*6=24 glVertex calls with the combinations of +/-1.0 or any different size. You can extract the vertexes from this example (in newer api)

complete GL+GLSL+VAO/VBO C++ example

so the code would be (C++):

const GLfloat vao_pos[]=
    {
//  x    y    z     //ix
    -1.0,+1.0,-1.0, //0
    +1.0,+1.0,-1.0, //1
    +1.0,-1.0,-1.0, //2
    -1.0,-1.0,-1.0, //3

    -1.0,-1.0,+1.0, //4
    +1.0,-1.0,+1.0, //5
    +1.0,+1.0,+1.0, //6
    -1.0,+1.0,+1.0, //7
    };

const GLuint vao_ix[]=
    {
    0,1,2,3,
    4,5,6,7,
    3,2,5,4,
    2,1,6,5,
    1,0,7,6,
    0,3,4,7,
    };

glBegin(GL_QUADS);
for (int i=0;i<24;i++) glVertex3dv(vao_pos+3*vao_ix[i]);
glEnd();

or this:

const GLfloat vao_pos[]=
    {
//  x    y    z     //ix
    -1.0,+1.0,-1.0, //0
    +1.0,+1.0,-1.0, //1
    +1.0,-1.0,-1.0, //2
    -1.0,-1.0,-1.0, //3

    -1.0,-1.0,+1.0, //4
    +1.0,-1.0,+1.0, //5
    +1.0,+1.0,+1.0, //6
    -1.0,+1.0,+1.0, //7

    -1.0,-1.0,-1.0, //3
    +1.0,-1.0,-1.0, //2
    +1.0,-1.0,+1.0, //5
    -1.0,-1.0,+1.0, //4

    +1.0,-1.0,-1.0, //2
    +1.0,+1.0,-1.0, //1
    +1.0,+1.0,+1.0, //6
    +1.0,-1.0,+1.0, //5

    +1.0,+1.0,-1.0, //1
    -1.0,+1.0,-1.0, //0
    -1.0,+1.0,+1.0, //7
    +1.0,+1.0,+1.0, //6

    -1.0,+1.0,-1.0, //0
    -1.0,-1.0,-1.0, //3
    -1.0,-1.0,+1.0, //4
    -1.0,+1.0,+1.0, //7
    };

glBegin(GL_QUADS);
for (int i=0;i<24*3;i+=3) glVertex3dv(vao_pos+i);
glEnd();

so just port it to python (I do not code in python) its really just an array and a loop ... you can also hardcode the 24 glVertex calls without loop ....

score 0 · Answer 2 · answered Jun 22 '19 at 06:51

0

A rubik's cube can be organized by an 3 dimensional array of 3x3x3 cubes. It seems to be easy to rotate a slice of the cube, but note if on slice is rotated the positions of the cube change and have to be reorganized. Not only the position changes, also the orientation of the (rotated) single cubes changes.

Check out this answer by rabbid, https://stackoverflow.com/a/54953213/7977581

Its very descriptive. Also he explains it in Python.

answered Jun 22 '19 at 06:51

Shujath

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8
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This is link only answer so it should be rather a comment instead. Anyway beige should be aware of the linked QA as well as the other one (mine) [Quaternion rotation do not works as excepted](https://stackoverflow.com/a/39024016/2521214) as we commented him (me and Rabbid76) with those in his [previous question](https://stackoverflow.com/q/56640083/2521214). Anyway this question is not about rotations but the cube rendering itself in the old style api ... which the linked answer contains but its inside a more complex code and hard to extract for those who do not know what they are doing yet. – Spektre Jun 22 '19 at 07:32

How do I render a matrix as a cube in OpenGL?

2 Answers2