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Assignment 2 Phase 1

Assignment 2 Phase 1. Transformation Back-face culling View frustum culling. Outline. Implement the transformation. Modelview transformation Projection transformation Perspective division Viewport transformation Implement back-face culling. Bonus: Implement view frustum culling.

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Assignment 2 Phase 1

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  1. Assignment 2 Phase 1 Transformation Back-face culling View frustum culling

  2. Outline • Implement the transformation. • Modelview transformation • Projection transformation • Perspective division • Viewport transformation • Implement back-face culling. • Bonus: Implement view frustum culling.

  3. Input and Output • Input: *.view *.obj *.mtl • Same as assignment 1 • Output: Wireframe of the obj with back-face culling

  4. Transformation 1/3 Modelview Matrix Projection Matrix Viewport Transformation Perspective Division Vertex Vertex = Projection * Modelview * Vertex ; Vertex.xyzw /= Vertex.w; Vertex = Viewport * Vertex;

  5. Model view gluLookAt( GLdouble eyex, GLdouble eyey, GLdouble eyez, GLdouble atx, GLdouble aty, GLdouble atz, GLdouble upx, GLdouble upy, GLdoubpe upz ); N = (eye - at)/|eye - at|; V = up – (N•up)N; |up| = 1.0 U = V x N ;

  6. Model view • Modelview = BT

  7. Projection • gluPerspective( GLdouble fovy, GLdouble aspect, GLdouble near, GLdouble far );

  8. Projection • n=near; • f=far; • t=n*tan( fovy *PI / 180.0 /2); • b= -t; • r= t* aspect; • l= -r;

  9. Projection • Projection = NSH =

  10. Perspective Division • x /= w; • y /= w; • z /= w; • w /= w;

  11. View Port • Viewport = TS • From [-1 , 1 ] to [0 , width (or height) ]

  12. Back-face culling • You can perform back-face culling in • World cord. • View cord. • ZN < 0 • Window cord. • Clock wise 1 Back face 3 2

  13. View frustum culling • eliminate the polygon that complete outside the view frustum. • Bonus: view frustum clipping • Remove the part of polygon that outside the view frustum.

  14. How to draw wireframe? • Render the image using glBegin(GL_LINE_LOOP); glVertex2i(x,y); … glEnd();

  15. What to do in reshape function? void GL_reshape(GLsizei w, GLsizei h){ glViewport(viewport->x, viewport->y, viewport->width, viewport->height); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluOrtho2D(viewport->x, viewport->width, viewport->y, viewport->height); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); }

  16. UI requirement • Show an input command line. • “Please input the file name.” • If I type “box”, then read box.obj and box.view etc.

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