Rename assignment 1 to 1a

assignment-0/ASSIGNMENT.md

@@ -1,3 +1,5 @@
+# Assignment 0: Working with ASCII images
+
 In this assignment, you are asked to write a program that creates an image in
 ASCII PPM format.
 
@@ -22,7 +24,7 @@ choose, the code you turn in **must** be your own.
 [3]: https://en.wikipedia.org/wiki/Kernel_(image_processing)
 [4]: https://en.wikipedia.org/wiki/Line_integral_convolution
 
-Detailed instructions:
+### Detailed instructions
 
 1.  Please use the following syntax to define the image size in your input file:
 
@@ -61,7 +63,7 @@ also be used to convert images from multiple other formats into ASCII PPM format
 
 [gimp]: http://www.gimp.org
 
-What you should turn in:
+### What you should turn in
 
 - a readme file that describes your what your program does
 - all of your source code, clearly commented

assignment-1a/ASSIGNMENT.md

@@ -0,0 +1,183 @@
+# Assignment 1a: Getting Started with Ray Casting
+
+In this assignment, you are asked to begin writing a basic ray casting program.
+
+This program should:
+
+1. read a simple scene description from a file that is provided as a command
+   line argument
+2. define an array of pixels that will hold a computer-generated image of the
+   scene
+3. use ray casting to determine the appropriate color to store in each pixel of
+   the output image
+4. write the rendered image to an output file in ascii PPM format
+
+As with assignment 0, the output file name should match the input file name
+except for the suffix. You can also earn extra credit by enabling your program
+to render a parallel projection and/or to render not only spheres but also
+cylinders.
+
+You are asked to run your program on multiple different input files, featuring a
+diverse range of different input parameter settings. One of the objectives of
+this assignment is to help you to develop an intuitive understanding of how each
+of the various input settings affects the appearance of the rendered scene.
+Please be sure to specifically consider these three questions:
+
+- How does the direction of the 'up' vector affect the rendered view of a scene?
+  You should specifically consider tipping the 'up' vector from side to side and
+  forward to back. You will want to define scenes with multiple objects,
+  asymmetrically arranged, to explore this question.
+- How do changes in the field of view settings affect the contents of your
+  rendered images?
+- How do various modifications of the viewing parameters affect the amount of
+  perspective distortion apparent in your image?
+
+In subsequent assignments you will be asked to extend the code you write for
+this assignment to incorporate additional effects like illumination, shadows,
+specular reflections and transparency, with these latter effects being achieved
+by recursive ray tracing. Be sure that your code is structured with these
+extensions in mind. In particular, you are advised to write simple, modular code
+following the example described in class.
+
+Please be sure to check the grading criteria to ensure that all requirements are
+understood.
+
+### Detailed instructions
+
+1.  Your program should read the following information from an input scene
+    description file (the syntax is shown below each item; entries in italics
+    are variables, entries in bold are keywords):
+
+    - The view origin, also variously referred to as the 'eye position', 'camera
+      position' or 'center of projection' (a 3D point in space)
+
+          eye   eyex eyey eyez
+
+    - The viewing direction (a 3D vector)
+
+          viewdir   vdirx  vdiry  vdirz
+
+    - The 'up' direction (a 3D vector)
+
+          updir   upx  upy  upz
+
+    - The horizontal field of view (in degrees, please)
+
+          hfov   fovh
+
+    - The size of the output image (in pixel units)
+
+          imsize   width  height
+
+    - The 'background' color (using r, g, b components defined on a scale from
+      0-1)
+
+          bkgcolor   r  g  b
+
+    - A 'material' color (in terms of r, g, b components defined on a scale from
+      0-1). The material color should be treated as a state variable, meaning
+      that all subsequently-defined objects should use the immediately-preceding
+      material color
+
+          mtlcolor   r  g  b
+
+    - A sequence of one or more objects. For this assignment, your program is
+      only required to be able to handle spheres. In subsequent assignments you
+      will be asked to extend your code to handle triangles, so you will want to
+      write your code with this future extension in mind. A sphere should be
+      defined by the coordinates of its center point (a 3D point in space) and
+      radius.
+
+          sphere   cx  cy  cz  r
+
+    - If you would like to attempt the extra credit portion of this assignment,
+      please use this format to define a parallel projection
+
+          projection  parallel
+
+    - If you would like to attempt the extra credit portion of this assignment,
+      please use this format to define a finite cylinder (without endcaps) that
+      is centered at the point (cx, cy, cz) and oriented in the direction (dirx,
+      diry, dirz).
+
+          cylinder   cx  cy  cz  dirx  diry  dirz  radius  length
+
+2.  Define an array of sufficient size to store the color values of your image.
+
+3.  Using knowledge of the view origin, viewing direction, up direction,
+    horizontal field of view and desired image aspect ratio, define an
+    appropriate “viewing window” in world coordinate space, and a 1-1 mapping
+    between points within this viewing window and pixel locations in your output
+    image.
+
+4.  For each pixel in the output image:
+
+    - Define the equation of the ray that begins at the view origin and passes
+      through the corresponding 3D point in the viewing window
+    - Then, for each object in the scene:
+      - Determine whether the current viewing ray intersects that object, and if
+        so at what point or points
+      - If there are one or more ray/object intersection points that are 'in
+        front of' the view origin with respect to the positive viewing
+        direction, determine which of them is closest to the view origin,
+        remembering that ray/object intersection points that are 'behind' the
+        view origin, with respect to the viewing direction, should be ignored
+      - Determine the color of the object at the closest forward ray/object
+        intersection point, if there is one, and return that value to be stored
+        at the appropriate location in your image array
+      - If no ray/object intersection is found, return the background color
+
+5.  After all of the rays have been cast and a color has been determined for
+    each pixel in the output image, write the final image to an output file,
+    using the ascii PPM format.
+
+You are strongly encouraged to begin with a very simple scene description,
+consisting for example of a single sphere located directly in front of the eye
+in the direction of view. You are also advised to begin by using a very small
+image size, to expedite the debugging process.
+
+To explore the effects of various scene parameters, you are advised to start by
+varying the values of just one viewing parameter at a time, such as: the eye
+position, the viewing direction, the direction of the ‘up’ vector, the vertical
+field of view, the image aspect ratio, etc. Once you understand the effect of
+each parameter in isolation, you should experiment with combinations of changes,
+such as: co-varying the field of view and the proximity of the eye to the
+objects in your scene. Your ability to appreciate the effects of different view
+settings will be improved if you use a relatively complex but intuitively
+organized scene, with some asymmetric features and not too much empty space. One
+example is: spheres centered at each of the 8 corners of a cube, using different
+colors for each corner, or cylinders arranged along each of the 12 edges of a
+cube.
+
+### What you should turn in
+
+- All of your source code, clearly commented, plus a ~~readme file with
+  compiling instructions or a~~ Makefile or CMake file that the TA can use to
+  compile your code.
+- One "showcase" image produced by your program, that I can share with the rest
+  of the class. To save time for the TA, we would be grateful if you could
+  provide this image in a format that is supported for direct display in Google
+  Slides or Powerpoint.
+- A 1-3 page writeup (including pictures) in which you discuss your observations
+  on how the key viewing parameters affect the appearance of the rendered scene.
+  Please incorporate sufficient images produced by your ray casting program to
+  illustrate and explain your findings. In your writeup, be sure to specifically
+  address each of these three points:
+  - How does the apparent rotation of the scene with respect to the viewpoint
+    change with changes in the direction of the ‘up’ vector?
+  - How do changes in the field of view settings affect the appearance of the
+    scene in your rendered image?
+  - How can the viewing parameters (e.g. the camera location, field of view
+    settings, …) be adjusted to achieve a less exaggerated vs more exaggerated
+    amount of apparent perspective distortion in your image?
+- Please submit all of the above as a single zip file, containing appropriate
+  subfolders, using the naming convention hw1a.firstname.lastname.zip. Please
+  do not use tar or rar or any other alternative compression mode that could
+  complicate the grading process for the TA.
+
+---
+
+Two sample input files with their corresponding output images are provided in
+the Files directory of this Canvas website. Please feel free to use these
+examples to partially check the functionality of your program. We will be
+testing your code on additional input files.