Assignment 4 Whitted Ray Tracing algorithm

 School of Computing
CS3241 Computer Graphics 
Lab Assignment 4

LEARNING OBJECTIVES
Implementing the Whitted Ray Tracing algorithm. After completing the programming assignment,
you should have learned
• how to compute ray intersection with some simple implicit-form surface primitive,
• how to do lighting computation,
• how to shoot shadow rays to generate shadows,
• how to spawn secondary rays,
• how to trace rays recursively, and
• how the Whitted Ray Tracing algorithm works.
TASKS
You are to complete an incomplete C++ program that implements the Whitted Ray Tracing
algorithm. You have to complete the program according to the following requirements. There are
altogether three tasks in the assignment.
Please download the ZIP file Lab4_todo_(*).zip from the Lab Assignments folder in LumiNUS
Files. A Visual Studio 2017 solution Main.sln (or Xcode project Main.xcodeproj on macOS) is
provided for you to build the executable program. If you build and run the given incomplete program,
it will produce an image as follows (in file out1.png).
It shows an image of an unlit scene of 3 intersecting planes and a cube made of triangles. Two
additional spheres are supposed to be in the image, but the ray-sphere intersection routine has not
been implemented yet.
National University of Singapore 2 / 5 School of Computing
Task 1
You are to complete the Sphere::hit() and Sphere::shadowHit() functions in Sphere.cpp
to compute ray-sphere intersection. You must write your code only in places marked “WRITE YOUR
CODE HERE”.
You can refer to Plane.{h, cpp} and Triangle.{h, cpp} to get some idea how to do it. Other
relevant files to study are Vector3d.h, Ray.h, Surface.h, and Sphere.h.
For this task, you have to submit your completed Sphere.cpp, and the image generated, which
should look like the following. You must name your image file img_spheres.png.
img_spheres.png
Task 2
You are to complete the Raytrace::TraceRay() function in Raytrace.cpp to perform the
recursive ray tracing. You must write your code only in places marked “WRITE YOUR CODE HERE”.
In this implementation, we are assuming that all objects are opaque. At each surface point
intersected by the ray, the color result is computed using the formula
𝐼 = 𝐼𝑙𝑜𝑐𝑎𝑙 + 𝑘𝑟𝑔 𝐼𝑟𝑒𝑓𝑙𝑒𝑐𝑡𝑒𝑑
where
𝐼𝑙𝑜𝑐𝑎𝑙 = 𝐼𝑎𝑘𝑎 + ∑ 𝑘𝑖,𝑠ℎ𝑎𝑑𝑜𝑤
𝑀
𝑖=1
𝐼𝑖,𝑠𝑜𝑢𝑟𝑐𝑒[𝑘𝑑
(𝑵 ∙ 𝑳𝑖
) + 𝑘𝑟
(𝑹𝑖
∙ 𝑽)
𝑛]
and M is the number of point light sources in the scene.
The relevant files to study first are Vector3d.h, Color.h, Ray.h, Material.h, Light.h,
Surface.h, Scene.h and Raytrace.h.
For this task, you have to submit your completed Raytrace.cpp, and the images generated by the
program, which should look like the followings. There are 6 images you need to submit, and you
must name them as shown at the bottom of each image shown below.
National University of Singapore 3 / 5 School of Computing
img_r0.png
reflectLevels = 0
hasShadow = false
img_r0s.png
reflectLevels = 0
hasShadow = true
img_r1.png
reflectLevels = 1
hasShadow = false
img_r1s.png
reflectLevels = 1
hasShadow = true
img_r2.png
reflectLevels = 2
hasShadow = false
img_r2s.png
reflectLevels = 2
hasShadow = true
National University of Singapore 4 / 5 School of Computing
Each of these images should take less than 10 seconds to produce. On my laptop, img_r2s.png
(the most time-consuming) took about 1 second. In your IDE (e.g. Microsoft Visual Studio, Xcode),
make sure you compile your program using the Release configuration.
Task 3
You are to complete the DefineScene2() function in Main.cpp to model a new scene for
rendering. You must write your code only in places marked “WRITE YOUR CODE HERE”.
You must use all the surface primitive types, namely, plane, sphere, and triangle, in your scene model.
This task will be assessed based on the fulfillment of the above basic requirements, on the technical
difficulty and object’s complexity, and on the aesthetics and creativity. Your scene model should be
rendered with reflectLevels=2 and hasShadow=true, and an image resolution of 640x480.
Name your image file img_scene2.png.
For this task, you have to submit your completed Main.cpp, and the generated image
img_scene2.png.
GRADING
The maximum marks for this programming assignment is 100, and it constitutes 8% of your total
marks for the module. The marks are allocated as follows:
• Task 1 –– 30 marks
• Task 2 –– 50 marks
• Task 3 –– 20 marks
▪ 10 marks –– basic requirements,
▪ 5 marks –– technical difficulty and object’s complexity,
▪ 5 marks –– aesthetics and creativity.
Note that marks will be deducted for bad coding style. If your program cannot be compiled and linked,
you get 0 (zero) mark.
Good coding style. Comment your code adequately, use meaningful names for functions and
variables, and indent your code properly. You must fill in your name, and NUS User ID in the header
comment.
National University of Singapore 5 / 5 School of Computing
SUBMISSION
For this assignment, you need to submit only the following 11 files:
• Sphere.cpp and img_spheres.png,
• Raytrace.cpp and img_r0.png, img_r0s.png, img_r1.png, img_r1s.png,
img_r2.png, img_r2s.png,
• Main.cpp and img_scene2.png.
You must put it/them in a ZIP file and name your ZIP file nus-user-id_lab4.zip. For example, if
your NUS User ID is e0123456, you should name your file e0123456_lab4.zip.
Note that you may be penalized for submitting non-required files.
Submit your ZIP file to the Lab 4 Submissions / Group T0x folder in LumiNUS Files, where T0x
is your officially allocated Tutorial group number. Before the submission deadline, you may upload
your ZIP file as many times as you want to the correct folder. We will take only your latest
submission. Once you have uploaded a new version to the folder, you must delete the old versions.
DEADLINE
Late submissions will NOT be accepted. The submission folder will automatically close at the
deadline.
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