CMPS 160 -- Fall 2017

CMPS 160 -- Prog 3

Early if time stamp is before midnight Nov 11, 2017.
On time if time stamp is before midnight Nov 12, 2017.
Late submissions will not be accepted/graded.

Objectives:

Apply transformations (translate, rotate, scale) to multiple objects using direct manipulation.

Description:

Create a simple scene modeler where the user can load multiple objects (GCs) and apply transformations to them. Such a program can be used to set up a scene. For the bonus feature below, you can also use this to create new models.

Bonus:

Using a combination of GCs, create a more complex object. For example, you can first create a ring; replicate these 4 times; and arrange them similar to the 5 interlocking rings representing the Olympics. Another possibility is to create your own variation of the banana slug. Many other possibilities exists. Be creative.

Details:

Object vs world coordinates. Each object is defined in its own coordinate system. This is referred to as the object coordinate. Objects are placed in the world coordinate system via a series of transformations. When an object is first read in (or created), you need to keep track of its extents in the object coordinate system. The extent refers to the range of x,y,z values when the object is centered at the origin. The object center is simply the average of all the object vertices. Any transformations on an object is relative to this configuration.
Set your world coordinate system so that the origin is at the center of a 1001 x 1001 x 1001 space.
Picking. Picking is done by left clicking on an object. You can pick on any GC that's currently visible. You indicate that an object has been picked by changing its color to gray (Ka = 0.5 0.5 0.5, rest of the materials are unchanged). You deselect an object by left clicking on the background. Doing so will revert the color of the previously picked object back to its original color. Only one object can be picked at any time. If you click on another object while you currently have a picked object, the picked object will be updated to the latest one.
Scaling. Scaling is applied to the picked object. If there's no picked object, then the following is a no-op. Scaling is achieved by turning the scroll wheel (find a mouse with a scroll wheel if you're using your laptop to do development). Scrolling up will increase the object, while scrolling down will decrease the object. Scaling is done uniformly on x,y,z dimensions. Scaling is specified with respect to the object coordinate system. Any single scaling operation can be up to 0.5 to 2 times its previous size. Scaling is cumulative.
Translation. Translation is applied to the picked object. If there's no picked object, then the following is a no-op. Translation is specified with respect to the world coordinate system. 2D movements on the image plane is specified by using the left button in conjunction with mouse movement. The displacement between a left mouse down event and the left mouse up event indicates the amount of movement to be applied to the picked object. To specify a movement in the world z direction, the vertical displacement between the middle mouse down event and the middle mouse up event is used.
Rotation. Rotation is applied to the picked object. If there's no picked object, then the following is a no-op. Rotation is specified with respect to the object coordinate system. The user indicates rotation by using the right button in conjunction with the mouse movement. A right mouse down with horizontal motion (displacement in x is much larger than displacement in y) until a mouse up event indicates a rotation about the z-axis of the object (not of the screen). A right mouse down with a vertical motion until a mouse up event indicates a rotation about the x-axis of the object. You are not required to do a rotation about the object's y-axis.
A potential source of confusion is the use of different coordinate systems. Transformations are carried out with respect to a coordinate system. Pay attention to the required coordinate system for the different transformations above.
Cumulative transformations? Successive transformations on an object is always relative to the object's most recent configuration. For example, if I translate an GC then I scale it, the scaling will change the size of the GC in-place and not relative to the origin. That is, the scaled GC will still be at the translated position, but scaled to the new size. Likewise, if I apply a rotation to the GC as my next transformation, the rotation is applied relative to the GC's axes at its current location in the world coordinate system. A typical way of handling this is to store the cumulative transformations to an GC in a matrix. Apply the inverse of this matrix before applying the latest transformation. And update the cumulative matrix with the latest transformation. Each object will have its own cumulative transformation matrix.

Resource:

Read the examples in chapters 2 and 3 of the Matsuda-Lea book.

Grading:

Rubric:

You start off with 100 points.  You earn additional credit by turning in your assignment
early and/or implementing additional features.  You lose credit for missing functionality,
incorrect results, poorly documented or formatted code, or not following instructions.

Below is a partial list:

- up to 10 points off for poor features.html file
- up to 10 points off for inadequate comments or hard-to-read code
- up to 10 points off for not following instructions
- up to 10 points off for special handling to grade your homework (usually
  because you did not check that it runs on the computers in the lab first).
- functionality points depending on importance

Make sure you:
a.  submit the right files you want us to grade,
b.  have tested your code on the browsers in the lab.
c.  follow the general instructions described in overview.html

Who graded your assignment based on your login name:
```
cole:	a - k
hugh:	l - z
```

Submission:

See course overview for instructions on what to submit and what not to submit.

Put materials in a folder named prog3 and zip it up. Submission must be done using the "submit" command from unix.ucsc.edu

submit cmps160-ap.f17 prog3 prog3.zip