CS293: Java Graphics with JOGL, Solutions

Transcription

1 UNIVERSITY OF SURREY c B.Sc. Undergraduate Programmes in Computing B.Sc. Undergraduate Programmes in Mathematical Studies Level HE2 Examination CS293: Java Graphics with JOGL, s Time allowed: 2 hours Spring Semester 2007 Answer THREE out of FOUR questions. All questions have equal weight and there are 33 marks for each question.

2 CS/2293/13/SS06 Page 1 The following list of JOGL methods and fields may or may not prove useful in the exam questions. In this list we have stuck with the conventions for object names that were used in the labs. GL gl = drawable.getgl() GLU glu = new GLU() GLUT glut = new GLUT() glshademodel glloadidentity glviewport(x,y,h,w) glu.glulookat (camerax, cameray, cameraz, lookatx, lookaty, lookatz, upx, upy, upz) glutwireteapot glmatrixmode gluperspective glbegin glvertex3f gltranslatef glrotated glpushmatrix glpopmatrix GL.GL PROJECTION GL.GL MODELVIEW glmaterialfv GL.GL SPECULAR GL.GL SHININESS gllightfv glenable SEE NEXT PAGE

3 CS/2293/13/SS06 Page 2 1. (a) Consider the following JOGL code snipet: public void init(glautodrawable drawable) { /* missing code here */ Modify this method so that it sets the clear colour to black and sets the shading model to flat [5 marks] public void init(glautodrawable drawable) { GL gl = drawable.getgl(); // gl.glclearcolor(0.0f, 0.0f, 0.0f, 0.0f); gl.glshademodel(gl.gl_flat); (b) Consider the following JOGL code snipet: public void reshape(glautodrawable drawable, int x, int y, int width, int height) { GL gl = drawable.getgl( ); GLU glu = new GLU(); Modify this code snipet so that it correctly defines the perspective for the OpenGL canvas so that near is -1.0, far is 2.0, the aspect ratio is 1.0 and the field of view is 30. Also modify the code so that it defines the view port to map the canvas origin to (0,0) and scales the canvas to fit the width and height of the frame that it will appear in. Dont forget that the matrix mode needs to be set to projection when modifying perspectives, and reset to model view mode afterwards. [10 marks] public void reshape(glautodrawable drawable, int x, int y, int width, int height) { GL gl = drawable.getgl( ); GLU glu = new GLU(); QUESTION 1 CONTINUES ON NEXT PAGE

4 CS/2293/13/SS06 Page 3 gl.glviewport(0, 0, width, height); gl.glmatrixmode(gl.gl_projection); gl.glloadidentity (); glu.gluperspective(30.0, 1.0, -1.0, 2.0); gl.glmatrixmode (GL.GL_MODELVIEW); (c) Modify the following code snippet so that it causes JOGL to display a wire teapot at the origin of width 3.0. [18 marks] public void display(glautodrawable drawable) { /* missing code goes here */ 3 marks per correct line of code till we hit 18 (so if they mess up on one line still get 18) public void display(glautodrawable drawable) { GL gl = drawable.getgl( ); GLU glu = new GLU(); GLUT glut = new GLUT(); gl.glclearcolor(0.0f, 0.0f, 0.0f, 0.0f); gl.glclear(gl.gl_color_buffer_bit); gl.glcolor3f(1.0f, 1.0f, 1.0f); glut.glutwireteapot(0.3); SEE NEXT PAGE

5 CS/2293/13/SS06 Page 4 2. (a) Consider the following JOGL method: public synchronized void display(glautodrawable drawable) { GL gl = drawable.getgl(); gl.glclear(gl.gl_color_buffer_bit); gl.glloadidentity(); glu.glulookat(12,2,12, 0,0,0, 0,1,0); gl.glcolor3f(0.0f, 1.0f, 0.0f); float tor_dim1 = 0.9f; float tor_dim2 = 2.0f; int tor_simplex = 20; glut.glutwiretorus(tor_dim1, tor_dim2, tor_simplex, tor_simplex); This causes a single wire torus to appear on screen, with center at the origin. Modify the code so that three tori appear next to each other. The left torus must be the result of translating the original torus 5.5f to the left along the x-axis. The right torus must be the result of translating the original torus 5.5f to right along the x-axis. [10 marks] glut.glutwiretorus(tor_dim1, tor_dim2, tor_simplex, tor_simplex); gl.gltranslatef(tor_dist, 0, 0); glut.glutwiretorus(tor_dim1, tor_dim2, tor_simplex, tor_simplex); gl.gltranslatef(-1.0f * tor_dist, 0, 0); glut.glutwiretorus(tor_dim1, tor_dim2, tor_simplex, tor_simplex); QUESTION 2 CONTINUES ON NEXT PAGE

6 CS/2293/13/SS06 Page 5 (b) Next modify the display method so that if the JOGL code were run with an FPSanimator object, then the whole scene would rotate about the origin. To do this change the glulookat code in the display method so that the point of view will rotate around a circle radius 12.0, with origin at point (0, 0, 0), and constantly looking at the origin, with the y-axis as up. [10 marks] /* new fields added to start protected float rot_view = 0f, rot_add = 0.05f; */ gl.glloadidentity(); glu.glulookat(12*math.cos(rot_view / (Math.PI*2)), 2, 12*Math.sin(rot_view / (Math.PI*2)), 0,0,0, // what im looking at 0,1,0); // up vector addrot(); //new method listed below /* end of snipet for display method */ private void addrot() { rot_view += rot_add; if (rot_view > 360f) rot_view -= 360; (c) Finally modify the display method so that if the JOGL code were run with an FPSanimator object, then each torus would spin around its own center, but remains at the same relative location with respect to the other tori in the scene. [13 marks] /* as above but with these additional lines added to the tori, where spin is added as a new field to class */ gl.glcolor3f(0.0f, 1.0f, 0.0f); gl.glrotatef(-1.0f *spin, 0.0f, 0.0f, 1.0f); glut.glutwiretorus(tor_dim1, QUESTION 2 CONTINUES ON NEXT PAGE

7 CS/2293/13/SS06 Page 6 tor_dim2, tor_simplex, tor_simplex); gl.glcolor3f(0.0f, 0.0f, 1.0f); gl.gltranslatef(tor_dist, 0, 0); gl.glrotatef(spin, 0.0f, 0.0f, 1.0f); glut.glutwiretorus(tor_dim1, tor_dim2, tor_simplex, tor_simplex); gl.glcolor3f(1.0f, 0.0f, 0.0f); gl.gltranslatef(-1.0f * tor_dist, 0, 0); gl.glrotatef( spin, 0.0f, 0.0f, 1.0f); glut.glutwiretorus(tor_dim1, tor_dim2, tor_simplex, tor_simplex); spin += 0.2f; // or some other small amount SEE NEXT PAGE

8 CS/2293/13/SS06 Page 7 3. (a) Consider the following method: public void init_lights (GL gl) { FloatBuffer light_position1 = FloatBuffer.wrap(new float[] { 1.0f, 1.0f, 1.0f, 0.0f ); FloatBuffer light_ambient1 = FloatBuffer.wrap(new float[] { 0.99f, 0.0f, 0.0f, 1.0f ); gl.glshademodel(gl.gl_smooth); gl.gllightfv(gl.gl_light1, GL.GL_POSITION, light_position1); /* missing code goes here */ Complete the missing code so that the method properly enables lighting in JOGL for light source 1. Ensure that the light source has ambient settings as defined by light ambient1, and is set in position light position1. Make sure that the effect of using this method within the init method for a JOGL application would be to switch on lighting as indicated. Also make sure that all material is also given some appropriate ambient parameters so that it will reflect light from the light source. [10 marks] FloatBuffer mat_ambient1 = FloatBuffer.wrap(new float[] { 0.35f, 0.0f, 0.0f, 1.0f ); gl.glmaterialfv(gl.gl_front, GL.GL_AMBIENT, mat_ambient1); gl.gllightfv(gl.gl_light1, GL.GL_AMBIENT, light_ambient1); gl.gllightfv(gl.gl_light1, GL.GL_POSITION, light_position1); gl.glenable(gl.gl_light1); gl.glenable(gl.gl_lighting); (b) Next modify your code for init lights so that it also sets up a second light source. This time make the second light source have diffuse parameters set to RGBA values of {1.0f, 1.0f, 1.0f, 0.0f. Choose the position for the light source to be different from the first. Also give the material diffuse parameters of {1.0f, 0.0f, 0.0f, 0.0f. [10 marks] /* inserted before the gl.glenable(gl.gl_lighting); */ FloatBuffer light_position0 = FloatBuffer.wrap(new float[] { 1.0f, -1.0f, -1.0f, 0.0f ); QUESTION 3 CONTINUES ON NEXT PAGE

9 CS/2293/13/SS06 Page 8 FloatBuffer light_diffuse0 = FloatBuffer.wrap(new float[] { 1.0f, 1.0f, 1.0f, 0.0f ); FloatBuffer mat_diffuse0 = FloatBuffer.wrap(new float[] { 1.0f, 0.0f, 0.0f, 1.0f ); gl.glmaterialfv(gl.gl_front, GL.GL_DIFFUSE, mat_diffuse0); gl.gllightfv(gl.gl_light0, GL.GL_DIFFUSE, light_diffuse0); gl.gllightfv(gl.gl_light0, GL.GL_POSITION, light_position0); gl.glenable(gl.gl_light0); (c) Use the following JOGL fields: GL.GL FOG GL.GL FOG MODE GL.GL EXP GL.GL FOG COLOR GL.GL FOG DENSITY GL.GL FOG HINT GL.GL DONT CARE to fill in the missing values from the fogon method to produce a method for switching fog on within the display method of a JOGL application. [13 marks] public void fogon(gl gl) { gl.glenable(/* missing */); FloatBuffer fogcolor = FloatBuffer.wrap(new float[] {0.0f, 0.0f, 0.0f, 1.0f); gl.glfogi(/* missing */, /* missing */); gl.glfogfv(/* missing */, fogcolor); gl.glfogf(/* missing */, 0.2f); gl.glhint(/* missing */, /* missing */); gl.glclearcolor(0.0f, 0.0f, 0.0f, 1.0f); public void fogon(gl gl) { gl.glenable(gl.gl_fog); FloatBuffer fogcolor = FloatBuffer.wrap(new float[] {0.0f, 0.0f, 0.0f, 1.0f); gl.glfogi(gl.gl_fog_mode, GL.GL_EXP); gl.glfogfv(gl.gl_fog_color, fogcolor); gl.glfogf(gl.gl_fog_density, 0.2f); QUESTION 3 CONTINUES ON NEXT PAGE

10 CS/2293/13/SS06 Page 9 gl.glhint(gl.gl_fog_hint, GL.GL_DONT_CARE); gl.glclearcolor(0.0f, 0.0f, 0.0f, 1.0f); SEE NEXT PAGE

11 CS/2293/13/SS06 Page 10 Figure 1: Texture mapping example 4. Suppose we want to have a JOGL application that loads in four images and attaches them to geometric objects and then displays them as in Figure 1 (a) Change the init method below so that it uses a quadratic object to hold all the necessary parameters for texture mapping GLUT library objects. Use the GLU.GLU SMOOTH vlaue for setting the normal vector generator method. This will require three extra lines of code where shown. [8 marks] public void init(glautodrawable gldrawable) { GL gl = gldrawable.getgl(); displayversions (gl, glu); initlights(gl); // Initialize OpenGL Light try { loadgltextures(gl); // all textures propely loaded catch (IOException e) { throw new RuntimeException(e); gl.glshademodel(gl.gl_smooth); QUESTION 4 CONTINUES ON NEXT PAGE

12 CS/2293/13/SS06 Page 11 gl.glclearcolor(0.0f, 0.0f, 0.0f, 0.0f); gl.glcleardepth(1.0); gl.glenable(gl.gl_depth_test); gl.gldepthfunc(gl.gl_lequal); gl.glhint(gl.gl_perspective_correction_hint, GL.GL_NICEST); /* set up quadratic */ /* set up normal vectors */ /* switch on automatic calculation for quadratic textures */ public void init(glautodrawable gldrawable) { GL gl = gldrawable.getgl(); displayversions (gl, glu); initlights(gl); // Initialize OpenGL Light try { loadgltextures(gl); // all textures propely loaded catch (IOException e) { throw new RuntimeException(e); gl.glshademodel(gl.gl_smooth); gl.glclearcolor(0.0f, 0.0f, 0.0f, 0.0f); gl.glcleardepth(1.0); gl.glenable(gl.gl_depth_test); gl.gldepthfunc(gl.gl_lequal); gl.glhint(gl.gl_perspective_correction_hint, GL.GL_NICEST); quadratic = glu.glunewquadric(); glu.gluquadricnormals(quadratic, GLU.GLU_SMOOTH); glu.gluquadrictexture(quadratic, true); (b) For your new version of init what additional three lines of code are required to enable 2D texture mapping, and enable spherical mapping for all geometric objects. Recall that this will require setting values for GL S and GL T so that their texture generation mode is spherical mapping mode. [8 marks] QUESTION 4 CONTINUES ON NEXT PAGE

13 CS/2293/13/SS06 Page 12 gl.glenable(gl.gl_texture_2d); gl.gltexgeni(gl.gl_s, GL.GL_TEXTURE_GEN_MODE, GL.GL_SPHERE_MAP); gl.gltexgeni(gl.gl_t, GL.GL_TEXTURE_GEN_MODE, GL.GL_SPHERE_MAP); (c) The following code is meant to make a texture be attached to a square as shown by the middle square in Figure 1. Fill in the missing parts to correct the code. gl.glbindtexture(gl.gl_texture_2d, textures[1]); gl.gltranslatef(0.0f, 0.0f, bck -39.0f); gl.glscalef( ((float)imagew[filter])/((float)imageh[filter]), 1.0f, 1.0f); gl.glbegin(gl.gl_quads); gl.glnormal3f(0.0f, 0.0f, 1.0f); gl.gltexcoord2f(/* missing */); gl.glvertex3f(-15.0f, -15.0f, 15.0f); /* missing */; gl.glvertex3f(15.0f, -15.0f, 15.0f); /* missing */; gl.glvertex3f(15.0f, 15.0f, 15.0f); /* missing */; gl.glvertex3f(-15.0f, 15.0f, 15.0f); gl.glend(); Correct the code. [17 marks] gl.glbindtexture(gl.gl_texture_2d, textures[1]); gl.gltranslatef(0.0f, 0.0f, bck -39.0f); gl.glscalef( ((float)imagew[filter])/((float)imageh[filter]), 1.0f, 1.0f); gl.glbegin(gl.gl_quads); gl.glnormal3f(0.0f, 0.0f, 1.0f); gl.gltexcoord2f(0.0f, 0.0f); QUESTION 4 CONTINUES ON NEXT PAGE

14 CS/2293/13/SS06 Page 13 gl.glvertex3f(-15.0f, -15.0f, 15.0f); gl.gltexcoord2f(1.0f, 0.0f); gl.glvertex3f(15.0f, -15.0f, 15.0f); gl.gltexcoord2f(1.0f, 1.0f); gl.glvertex3f(15.0f, 15.0f, 15.0f); gl.gltexcoord2f(0.0f, 1.0f); gl.glvertex3f(-15.0f, 15.0f, 15.0f); gl.glend();