The design of framework references "Realistic Ray Tracing" by Peter Shirley and R.
Keith Morley<br>
All images (512x512) are adaptive sampleing with 2 levels of subdivision,
with Hall illumination model<br>
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After I changed Cs and Cd parameters, here's an image. I looked up OpenGL
material website and picked the one for pearl. Because I want to
avoid changing my code as much as possible, every object except the
floor uses "pearl" as material (i.e. the same Cs and Cd values).<br>
<img src="artImage/shadowOnly.png"><br>
<a href=artImage/shadowOnly.png>shadowOnly.png</a><br>
Running time: 110 + 602 seconds
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Here's an image with one level of reflection(every object except
the floor is reflective).<br>
<img src="oneLevel.png"><br>
<a href=oneLevel.png>oneLevel.png</a><br>
Running time: 141 + 765 seconds-->
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Here's an image with recursive reflection(the green sphere, yellow
sphere and the red cow are reflective).<br>
<img src="artImage/allLevel.png"><br>
<a href=artImage/allLevel.png>allLevel.png</a><br>
Running time: 141 + 1173 seconds
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Here's another image with different color parameters and recursive reflection(the green sphere, yellow
sphere and the red cow are reflective).<br>
<img src="artImage/adaptiveSampled_glass.png"><br>
<a href=artImage/adaptiveSampled_glass.png>adaptiveSampled_glass.png</a><br>
Running time: 149 + 1251 seconds
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In this image, everything is reflective.<br>
<img src="artImage/adaptiveSampled_allObjects.png"><br>
<a href=artImage/adaptiveSampled_allObjects.png>adaptiveSampled_allObjects.png</a><br>
Running time: a long time
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Here's one image with wrong shading parameters..<br>
<img src="artImage/shadow.png"><br>
<a href=artImage/wrongParam.png>wrongParam.png</a><br>
Running time: lost this record, but pretty fast 
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<!--In this image, everything is reflective and the camera is zoomed out.<br>
<img src="zoomedout.png"><br>
<a href=zoomedout.png>zoomedout.png</a><br>
Running time: 42 + 259 seconds
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Notice in the images above, there's one level of reflection. So I
added recursion to reflection. Here's an image with recursive
reflection, everything but the ground is reflective.<br>
<img src="recursive.png"><br>
<a href=recursive.png>recursive.png</a><br>
Running time: 147 + 925 seconds
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Here is a zoomed image where everything is reflective, including
the ground.<br>
<img src="recursive_zoomedout.png"><br>
<a href=recursive_zoomedout.png>recursive_zoomedout.png</a><br>
Running time: 51 + 440 seconds
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I feel like I'm just hacking to make the color look right. For one
object, its diffusion component and specular component are the same. Ambient
component depends on the situation, whether that pixel is in shade
or is on a reflective object.<br>
Also, shooting secondary ray is very tricky. I had to move the hit
point a little bit away from the object to get rid of the floating
point error.-->