CSE4020 - Computer Graphics - Lab Assignment 8 - Solved

1. Write down a Python program to draw a transformed triangle in a 3D space. 

A.     Set the window title to your student ID and the window size to (480,480).  

B.     Use the following code snippet:  

gCamAng = 0 

gComposedM = np.identity(4) 

 def render(M, camAng):     # enable depth test 

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)     glEnable(GL_DEPTH_TEST) 

 

    glLoadIdentity() 

 

    # use orthogonal projection      glOrtho(-1,1, -1,1, -1,1) 

 

    # rotate "camera" position to see this 3D space better      gluLookAt(.1*np.sin(camAng),.1, .1*np.cos(camAng), 0,0,0, 0,1,0) 

 

      # draw coordinate: x in red, y in green, z in blue     glBegin(GL_LINES)     glColor3ub(255, 0, 0)     glVertex3fv(np.array([0.,0.,0.]))     glVertex3fv(np.array([1.,0.,0.]))     glColor3ub(0, 255, 0)     glVertex3fv(np.array([0.,0.,0.]))     glVertex3fv(np.array([0.,1.,0.]))     glColor3ub(0, 0, 255)     glVertex3fv(np.array([0.,0.,0]))     glVertex3fv(np.array([0.,0.,1.]))     glEnd() 

 

    # draw triangle     glBegin(GL_TRIANGLES)     glColor3ub(255, 255, 255) 

    glVertex3fv((M @ np.array([.0,.5,0.,1.]))[:-1])     glVertex3fv((M @ np.array([.0,.0,0.,1.]))[:-1])     glVertex3fv((M @ np.array([.5,.0,0.,1.]))[:-1])     glEnd() 

 def key_callback(window, key, scancode, action, mods):     global gCamAng, gComposedM     if action==glfw.PRESS or action==glfw.REPEAT: 

         if key==glfw.KEY_1: 

            gCamAng += np.radians(-10)         elif key==glfw.KEY_3:             gCamAng += np.radians(10) 

 

 

C.     If you press or repeat a key, the triangle should be transformed as shown in the Table. Note that key 1 and 3 are already implemented in the above code snippet. 

Key Transformation 
 
Q        Translate by -0.1 in  x direction w.r.t global coordinate 
 
E        Translate by 0.1 in x direction w.r.t global coordinate 
 
A       Rotate about y axis by -10 degrees w.r.t local coordinate 
 
D       Rotate about y axis by +10 degrees w.r.t local coordinate 
 
W       Rotate about x axis by -10 degrees w.r.t local coordinate 
 
S        Rotate about x axis by +10 degrees w.r.t local coordinate 
 
 
1 
Rotate camera -10 degree 
 
3 
Rotate camera 10 degree 
 
 
 
 
D.     Transformations should be accumulated (composed with previous one). 

 

2. Write down a Python program to draw a hierarchical model of boxes. 

A.     Set the window title to your student ID and the window size to (480,480). 

B.     Start from the following code skeleton. 

import glfw 

from OpenGL.GL import * import numpy as np from OpenGL.GLU import * 

 def render():     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)     glEnable(GL_DEPTH_TEST) 

 

    glMatrixMode(GL_PROJECTION)     glLoadIdentity() 

    glOrtho(-2,2, -2,2, -1,1) 

 

    glMatrixMode(GL_MODELVIEW)     glLoadIdentity() 

     

    drawFrame() 

    t = glfw.get_time() 

 

# blue base transformation     glPushMatrix() 

    glTranslatef(np.sin(t), 0, 0) 

 

    # blue base drawing     glPushMatrix()     glScalef(.2, .2, .2)     glColor3ub(0, 0, 255)     drawBox()     glPopMatrix() 

 

    # red arm transformation     glPushMatrix() glRotatef(t*(180/np.pi), 0, 0, 1) 

    glTranslatef(.5, 0, .01) 

 

    # red arm drawing     glPushMatrix()     glScalef(.5, .1, .1)     glColor3ub(255, 0, 0)     drawBox()     glPopMatrix() 

 

    glPopMatrix()     glPopMatrix() 

 
def drawBox():     glBegin(GL_QUADS) 

    glVertex3fv(np.array([1,1,0.]))     glVertex3fv(np.array([-1,1,0.]))     glVertex3fv(np.array([-1,-1,0.]))     glVertex3fv(np.array([1,-1,0.]))     glEnd() 

 def drawFrame(): 

    # draw coordinate: x in red, y in green, z in blue     glBegin(GL_LINES)     glColor3ub(255, 0, 0) 

    glVertex3fv(np.array([0.,0.,0.]))     glVertex3fv(np.array([1.,0.,0.]))     glColor3ub(0, 255, 0) 

    glVertex3fv(np.array([0.,0.,0.]))     glVertex3fv(np.array([0.,1.,0.]))     glColor3ub(0, 0, 255) 

    glVertex3fv(np.array([0.,0.,0]))     glVertex3fv(np.array([0.,0.,1.]))     glEnd() 

 def main():     if not glfw.init():         return 

    window = glfw.create_window(480,480,'2017123456-lab6-1', None,None)     if not window:         glfw.terminate()         return 

    glfw.make_context_current(window)     glfw.swap_interval(1) 

     while not glfw.window_should_close(window):         glfw.poll_events()         render() 

        glfw.swap_buffers(window) 

 

    glfw.terminate() 

 if __name__ == "__main__":     main() 
C.     Add a green arm at the end of the red arm, and rotate the green arm about its local z axis. 

                i.       Render the green arm using drawBox(). 

D.     Also render local frames of the blue base, red arm, green arm using drawFrame(). 

E.     Expected result: Uploaded LabAssignment8-2.mp4