I average the vertices to nd a central point 35 35

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Unformatted text preview: lue at the centre of the quadrilateral. i) Average the vertices to find a central point [3.5, 3.5, 11.25]. ii) Find the light source direction [ 3.5, 11.25]. pp iii) Compute n · l = (0 + 3.5 + 22.5)/(|n||l|) = 24/( 5 151.06) = 0.95 3.5, iv) The final shading value is 0.95 ⇥ (255, 255, 255) = (242.25, 242.25, 242.25). Marks: The five parts carry, respectively, 25%, 15%, 20%, 20%, and 20% of the marks. 4 R2 Ray Tracing " ay tracing a The scene in the figure below has a mirror, a white paper box and two lights: Light&1& White& paper& box& (diffuse)& Eye& Light&2& & 50%&reflec8ve&red& mirror& i) Starting from the eye ray drawn, draw all additional reflection, refraction and shadow rays needed to compute the colour of the eye ray. Label each ray clearly. ii) Write down a formula which describes the computation of the colour for the ray. Label your drawing from a part i) or add annotations to your terms in your equation so that it is clear what is being computed. b Briefly explain which illumination effects can be achieved with ray tracing and mirror& i) Starting from the eye ray drawn, draw all additional reflection, refraction and shadow rays needed to compute the colour of the eye ray. Label each ray clearly. Ray tracing" Light&1& Shadow&S2& Eye& Shadow&S1& Reflec8on& White& paper& box& (diffuse)& Shadow&S3& Light&2& & Shadow&S4& 50%&reflec8ve&red& mirror& Marks: ii) Write down a formula which describes the computation of the colour for the ray. Label your drawing from a part i) or add annotations to your terms in your equation so that it is clear what is being computed. 3 i) Starting from the eye ray drawn, draw all additional reflection, refraction and shadow rays needed to compute the colour of the eye ray. Label each ray clearly. Ray tracing"a formula which describes the computation of the colour for ii) Write down the ray. Label your drawing from a part i) or add annotations to your terms in your equation so that it is clear what is being computed. b Briefly explain which illumination effects can be achieved with ray tracing and how these effects are achieved. What is the key difference between ray tracing and radiosity? c A ray originates at point V and is parallel with direction vector d. A right-angled triangle is given by three points P1 , P2 and P3 (the right angle is at point P1 ). Show in detail how you can calculate the intersection between the ray and the face defined by the triangle. d In a concrete example, a ray starts at V = (7, 7, 0) and has a direction vector d = (0, 0, 1). The points of the triangle are given as P1 = (6, 6, 10), P2 = (12, 6, 10), and P3 = (6, 10, 5). Calculate whether the ray intersects the face defined by the triangle. The four parts carry, respectively, 30%, 20%, 30%, and 20% of the marks. c A ray originates at point V and is parallel with...
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This document was uploaded on 03/26/2014.

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