Computer Graphics-Lab Assignment 5 Solved

1.     Write down a Python program to draw a transformed triangle and its local frame in a 3D space. A. Set the window title to your student ID and the window size to (480,480). 

B.     Use the following drawFrame() and drawTriangle() to draw the frame and triangle: 

def drawFrame():
 
    glBegin(GL_LINES)
 
    glColor3ub(255, 0, 0)
 
    glVertex2fv(np.array([0.,0.]))     glVertex2fv(np.array([1.,0.]))
    glColor3ub(0, 255, 0)
 
    glVertex2fv(np.array([0.,0.]))     glVertex2fv(np.array([0.,1.]))
    glEnd()
 
 
 
 
 
 
 

def drawTriangle():
 
    glBegin(GL_TRIANGLES)
 
    glVertex2fv(np.array([0.,.5]))     glVertex2fv(np.array([0.,0.]))     glVertex2fv(np.array([.5,0.]))
    glEnd()
 
 
 
 
 
 
C.     First draw an untransformed white triangle and a global frame. 

D.     Then draw a transformed blue triangle and its local frame. The triangle should be first rotated by 30 degrees and then translated by (0.6, 0, 0) w.r.t. the global frame. E. Expected result:  

               i.          

F. Files to submit: A Python source file (Name the file whatever you want (in English). Extension should be .py) 

 

2.     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 (we'll see details later)     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)     glEnable(GL_DEPTH_TEST) 

 

    glLoadIdentity() 

 

    # use orthogonal projection (we'll see details later)     glOrtho(-1,1, -1,1, -1,1) 

 

    # rotate "camera" position to see this 3D space better (we'll see details later) 

    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). 

i. You’ll need two global variables to store current accumulated transformation and current camera angle.