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# Why are my cubes randomly rotating a few seconds into animation?

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### #1JoryRFerrell  Members   -  Reputation: 143

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Posted 15 February 2013 - 04:47 PM




Why are my cubes randomly rotating near the end of their animation? Also, why is the flat, stationary plane drawing with one edge"bending" into the origin?


SCREEN_SIZE = (800, 600)

import sys

from OpenGL.GL import *
from OpenGL.GLU import *

import pygame
from pygame.locals import *

from gameobjects.matrix44 import *
from gameobjects.vector3 import *
import random

def resize(width, height):

glViewport(0, 0, width, height)
glMatrixMode(GL_PROJECTION)
gluPerspective(90.0, float(width)/height, 0.1, 10000.0)
glMatrixMode(GL_MODELVIEW)

def init():

glEnable(GL_DEPTH_TEST)

glClearColor(1.0, 1.0, 1.0, 1.0)

glEnable(GL_COLOR_MATERIAL)

glEnable(GL_LIGHTING)
glEnable(GL_LIGHT0)
glLight(GL_LIGHT0, GL_POSITION,  (10, 10, 10, 0))

class ground(object):
def __init__(self):
self.position = (0.0, 0.0, 0.0)
self.color = tuple([random.uniform(0.0,1.5), random.uniform(0.0,1.5) , random.uniform(0.0,1.5)])

def render(self):
glColor(0.0, 1.0, 1.0)

glNormal(0.0, 0.0, 1.0)
glVertex3f(1.000000, 0.000000, 1.000000)
glVertex3f(-1.000000, 0.000000, 1.000000)
glVertex3f(1.000000, 0.000000, -1.000000)
glVertex3f(-1.000000, 0.000000, -1.0000000)

glEnd()

class Cube_Projectile(object):

def __init__(self, position):

self.position = (0.0, 0.0, 0.0)
self.color = tuple([random.uniform(0.0,1.0), random.uniform(0.0,1.0) , random.uniform(0.0,1.0)])
self.life = 1000

def render(self):

if self.life > 0:

glColor(self.color)

# Adjust all the vertices so that the cube is at self.position
# vertices = [tuple(Vector3(v) + self.position) for v in self.vertices]

# Draw all 6 faces of the cube

self.life -= 1

glTranslatef(self.position[0], self.position[1], self.position[2])
glRotate(30, 1, 1, 0)

glNormal3f(1.000000, 0.000000, 0.000000)
glVertex3f(-2.000000, -2.000000, -2.000000)
glVertex3f(-2.000000, -2.000000, 2.000000)
glVertex3f(-2.000000, 2.000000, 2.000000)
glVertex3f(-2.000000, 2.000000, -2.000000)

glNormal3f(0.000000, 0.000000, 1.000000)
glVertex3f(-2.000000, 2.000000, -2.000000)
glVertex3f(2.000000, 2.000000, -2.000000)
glVertex3f(2.000000, -2.000000, -2.000000)
glVertex3f(-2.000000, -2.000000, -2.000000)

glNormal3f(-1.000000, 0.000000, -0.000000)
glVertex3f(2.000000, 2.000000, -2.000000)
glVertex3f(2.000000, 2.000000, 2.000000)
glVertex3f(2.000000, -2.000000, 2.000000)
glVertex3f(2.000000, -2.000000, -2.000000)

glNormal3f(0.000000, 0.000000, -1.000000)
glVertex3f(-2.000000, -2.000000, 2.000000)
glVertex3f(2.000000, -2.000000, 2.000000)
glVertex3f(2.000000, 2.000000, 2.000000)
glVertex3f(-2.000000, 2.000000, 2.000000)

glNormal3f(0.000000, -1.000000, 0.000000)
glVertex3f(-2.000000, -2.000000, 2.000000)
glVertex3f(-2.000000, -2.000000, -2.000000)
glVertex3f(2.000000, -2.000000, -2.000000)
glVertex3f(2.000000, -2.000000, 2.000000)

glNormal3f(0.000000, 1.000000, 0.000000)
glVertex3f(2.000000, 2.000000, 2.000000)
glVertex3f(2.000000, 2.000000, -2.000000)
glVertex3f(-2.000000, 2.000000, -2.000000)
glVertex3f(-2.000000, 2.000000, 2.000000)

glEnd()

glRotate(-30, -1, -1, 0)
glTranslatef(-self.position[0], -self.position[1], -self.position[2])

def run():

pygame.init()
screen = pygame.display.set_mode(SCREEN_SIZE, HWSURFACE|OPENGL|DOUBLEBUF)

resize(*SCREEN_SIZE)
init()

clock = pygame.time.Clock()

glMaterial(GL_FRONT, GL_AMBIENT, (0.1, 0.1, 0.1, 1.0))
glMaterial(GL_FRONT, GL_DIFFUSE, (1.0, 1.0, 1.0, 1.0))

# Camera transform matrix
camera_matrix = Matrix44()
camera_matrix.translate = (10.0, 2.0, 20.0)

# Initialize speeds and directions
rotation_direction = Vector3()
movement_direction = Vector3()
movement_speed = 5.0

objects_Render = []
ground_1 = ground()
objects_Render.append(ground_1)

mouse_pos = pygame.mouse.get_pos()

while True:

for event in pygame.event.get():
if event.type == QUIT:
return
if event.type == KEYUP and event.key == K_ESCAPE:
return

# Clear the screen, and z-buffer

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

time_passed = clock.tick()

time_passed_seconds = time_passed / 1000.

pressed = pygame.key.get_pressed()

# Reset rotation and movement directions

rotation_direction.set(0.0, 0.0, 0.0)

movement_direction.set(0.0, 0.0, 0.0)

# Modify direction vectors for key presses
if pressed[K_LEFT]:
rotation_direction.y = +1.0
elif pressed[K_RIGHT]:
rotation_direction.y = -1.0
if pressed[K_UP]:
rotation_direction.x = +1.0
elif pressed[K_DOWN]:
rotation_direction.x = -1.0
if pressed[K_d]:
rotation_direction.z = -1.0
elif pressed[K_a]:
rotation_direction.z = +1.0
if pressed[K_w]:
movement_direction.z = -5.0
elif pressed[K_s]:
movement_direction.z = +5.0

if pygame.mouse.get_pressed()[0]:
print pygame.mouse.get_pressed()[0]
new_mouse_pos = pygame.mouse.get_pos()

if new_mouse_pos != mouse_pos:

# rotation_direction.z = (float(new_mouse_pos[0]) - (mouse_pos[0]))/2.0
if new_mouse_pos > mouse_pos:
rotation_direction.z = ((1.0*new_mouse_pos[0]) - (1.0*mouse_pos[0]))/360

elif new_mouse_pos < mouse_pos:
rotation_direction.z = -((1.0*mouse_pos[0]) - (1.0*new_mouse_pos[0]))/360

if new_mouse_pos[0] > mouse_pos[0]:
rotation_direction.x = SCREEN_SIZE[1]/60.0 * .1

elif new_mouse_pos[0] > mouse_pos[0]:
rotation_direction.x = SCREEN_SIZE[1]/60.0 * -.1

mouse_pos = new_mouse_pos

mouse_pos = (0, 1)

if pressed[K_n]:

# Beginning of objects_Render.append()
objects_Render.append(Cube_Projectile((0.0,0.0,0.0))) # End of objects_Render.append()

# Calculate rotation matrix and multiply by camera matrix
rotation = rotation_direction * rotation_speed * time_passed_seconds
rotation_matrix = Matrix44.xyz_rotation(*rotation)
camera_matrix *= rotation_matrix

# Calcluate movment and add it to camera matrix translate
movement = heading * movement_direction.z * movement_speed
camera_matrix.translate += movement * time_passed_seconds

# Upload the inverse camera matrix to OpenGL

# Light must be transformed as well
glLight(GL_LIGHT0, GL_POSITION,  (0, 1.5, 1, 7))

print event.type

for obj in objects_Render:

"""
print "Object: ", objects_Render.index(obj)
print "Object Position: ", obj.position, "\n"
"""

tup = []
tup.append(obj.position[0] + random.uniform(-0.70,0.50))
tup.append(obj.position[1] + random.uniform(-0.70,0.50))
tup.append(obj.position[2] + random.uniform(-0.70,0.50))
obj.position = tuple(tup)

obj.render()

# Show the screen
pygame.display.flip()

run()


### #2__SKYe  Members   -  Reputation: 860

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Posted 16 February 2013 - 07:39 PM

First, when you draw you call



glRotatef(30, 1, 1, 0)


And after drawing you call:



glRotatef(-30, -1, -1, 0)


. To reverse the rotation, you only need to change the sign of the degrees, not the axis, so it should be:



glRotatef(-30, 1, 1, 0);


To avoid this (and to make it easier), instead of doing this:



glTranslatef(self.position[0], self.position[1], self.position[2])
glRotate(30, 1, 1, 0)

... draw ...

glRotate(-30, 1, 1, 0)
glTranslatef(-self.position[0], -self.position[1], -self.position[2])


do



glPushMatrix();
glTranslatef(self.position[0], self.position[1], self.position[2])
glRotate(30, 1, 1, 0)

... draw ...

glPopMatrix();


This way, between glPushMatrix() and glPopMatrix(), you can do whatever transformations you want, that it won't affect the previous matrix.

I don't know if this is exactly your problem, but when you draw the cubes, you're translating them first and then rotating.

In this case, the farther away the cube is from the origin, the longer will be the rotation, because it will be rotating around the axis and not around itself.

Again, i don't know if this is intentional or not, if it is then forget it.

I don't really know Python, but this seems to be a problem with OpenGL, so i hope it helps.

Also, unless the OpenGL spec is different for Python, shouldn't the glRotate() call be glRotatef() (or glRotated() if your using doubles)?

Edited by __SKYe, 16 February 2013 - 07:43 PM.

### #3Bacterius  Crossbones+   -  Reputation: 7047

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Posted 17 February 2013 - 01:27 AM

Also, unless the OpenGL spec is different for Python, shouldn't the glRotate() call be glRotatef() (or glRotated() if your using doubles)?

Python doesn't really make a distinction between float and double, being dynamically typed, so I'd assume it chooses the proper function under the hood and casts as needed. Having glRotatef and glRotated exposed wouldn't be pythonic

Edited by Bacterius, 17 February 2013 - 01:27 AM.

"The best comment is a deleted comment."

### #4JoryRFerrell  Members   -  Reputation: 143

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Posted 17 February 2013 - 03:28 PM

First, when you draw you call



glRotatef(30, 1, 1, 0)


And after drawing you call:



glRotatef(-30, -1, -1, 0)


. To reverse the rotation, you only need to change the sign of the degrees, not the axis, so it should be:



glRotatef(-30, 1, 1, 0);


To avoid this (and to make it easier), instead of doing this:



glTranslatef(self.position[0], self.position[1], self.position[2])
glRotate(30, 1, 1, 0)

... draw ...

glRotate(-30, 1, 1, 0)
glTranslatef(-self.position[0], -self.position[1], -self.position[2])


do



glPushMatrix();
glTranslatef(self.position[0], self.position[1], self.position[2])
glRotate(30, 1, 1, 0)

... draw ...

glPopMatrix();


This way, between glPushMatrix() and glPopMatrix(), you can do whatever transformations you want, that it won't affect the previous matrix.

I don't know if this is exactly your problem, but when you draw the cubes, you're translating them first and then rotating.

In this case, the farther away the cube is from the origin, the longer will be the rotation, because it will be rotating around the axis and not around itself.

Again, i don't know if this is intentional or not, if it is then forget it.

I don't really know Python, but this seems to be a problem with OpenGL, so i hope it helps.

Also, unless the OpenGL spec is different for Python, shouldn't the glRotate() call be glRotatef() (or glRotated() if your using doubles)?

Cool beans. You answered my question and you helped me a lot with the info on Push and Pop funcs. I had read about them but I didn't really pay attention. Patience is not my strong suit. As for calling rotation before translation, it wasn't intentional, but I didn't really care. I have read in the bookmthat provided a large part of this code, that you should rotate before translation because trans affects rotation, but for now, I was just worried about fooling around with rots. As for the diff between rotatef and rotated,

I have noticed no I'll effect's in the program.

### #5JoryRFerrell  Members   -  Reputation: 143

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Posted 17 February 2013 - 03:33 PM

Also, as for the ground_1 object rendering weirdly....I screwed up the order of the verts. Instead of writing them in the order they appeared in the face, I simply wrote each verts in the order they appeared in list of all verts. The result was that the last 2 verts are actually supposed to be switched, but I failed to do so. So IT WAS rendering properly, just not how I expected it to.

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