How to Rotate a object3D in PyOpenGL?

Question

I am trying to rotate one object in the X-axis, but I don't get.

I have a class Object 3D it's:

class Object3D():
   implements( IRenderizable )

   def __init__(self, parameters={} ):
     self.parameters = parameters
     self.ID= Engine().addObject3D()
     self.parent = None
     self.childrens =[]
     self.position = (parameters.get('POSITION') is None ) is True and  Vector4()     or parameters.get('POSITION')
     self.rotation = (parameters.get('ROTATION') is None ) is True and  Quaternion() or parameters.get('ROTATION')
     self.direction = Vector4()
     self.scale = Vector3(1,1,1)
     self.matrix = Matrix4()
     self.matrixLocal = Matrix4()
     self.matrixWorld = Matrix4()
     self.matrixRotationWorld = Matrix4()
     self.up = Vector3(0,1,0 )
     self.parameters =parameters
     self.rotationAngle= 10.
     self.currentMatrix = None
     self.initCurrentMatrix()


def initCurrentMatrix(self):
    glPushMatrix()
    glLoadIdentity()
    self.currentMatrix = glGetDoublev(GL_MODELVIEW_MATRIX)
    glPopMatrix()
    return 

def setID(self, Id ):
    self.ID = Id

def moveTo( self, x,y,z ):
    v=Vector4(x,y,z)
    #self.position.addSelf( self.rotation.rotateVector(v)  )
    self.position.addSelf( v )
    glPushMatrix()
    glLoadIdentity()
    glTranslatef( float(self.position.x),float(self.position.y),float(self.position.z) )
    self.currentMatrix =  glGetDoublev(GL_MODELVIEW_MATRIX)
    glPopMatrix()
    return self

def render(self):
    pass

In this chunk of code you see how to implements the rotation:

def rotateX(self, angle=2 ):
    glPushMatrix()
    glRotated( angle, 0,1,0)
    glPopMatrix()
    return self

when Vector4, Vector3 , Quaternion, Matrix4 are my own classes.

what this my mistake? and How to make a Rotation?

score 4 · Answer 1 · edited Jan 16 '13 at 14:43

I don't know, whether it helps, but the general workflow for moving or rotating an object is like the following:

draw static stuff
push actual matrix on stack (glPushMatrix)
load identity matrix (initial matrix) (glLoadIdentity)
use your own matrix and load and set it as the actual matrix
transform the actual matrix via glRotate / gl....
save the actual matrix as your own matrix
draw your object
pop matrix from stack (glPopMatrix)
draw rest of the static stuff

In step 5/6 you have updated your transformation matrix. This is necessary, because glRotate is like a makro for multiply an rotation matrix onto the actual transformation matrix. If you always load the identity matrix and then do an glRotate then it transforms the identity matrix by only the given degree --> your object will be drawn rotated by this degree and then never do something else - i guess, this is your fault...

if you use the 9 steps above, the matrix for your object will be multiplied by the rotation matrix and the result is used for the next multiply in the next iteration step.

I hope, this will help in general understanding =)

score 2 · Answer 2 · answered Dec 12 '12 at 22:08

2

In your rotate func, it should be degrees not angle:

glRotatef(degrees, 0, 0, -1)

Does that work?

answered Dec 12 '12 at 22:08

Uchiha Madara

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1
5

score 0 · Answer 3 · answered Nov 04 '12 at 01:24

0

what this my mistake?

You mistake OpenGL for a math library, which it is not. Do not use OpenGL for doing math on matrices you keep around in some variable. Actually, don't use OpenGL matrix functions at all. They're part of the fixed function pipeline and have been removed from later versions of OpenGL.

answered Nov 04 '12 at 01:24

datenwolf

159,371
13
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So, how to make a rotation without PyOpenGL? – Cristian Nov 04 '12 at 18:43
In 3D graphics transformations are represented as 4×4 matrices. A rotation can be expressed as such a matrix. Each of your objects would carry a transformation matrix, that describes its position in the world. Changes to that matrix are expressed by multiplying the matrix describing that change onto it. When drawing the object you first calculate the composition matrix of view transform (sort of your camera) and the object's transform matrix and pass that as a uniform to the vertex shader. Together with the projection matrix (sort of the lens of the camera) this defines the full transformation – datenwolf Nov 04 '12 at 20:00

How to Rotate a object3D in PyOpenGL?

3 Answers3