CS465 Program 1: Ray I

• assignment handout | framework code, sample input and images

watch this space for additional helpful material.

FAQ

• 4:55 pm, 31 August 2005: Updated the Camera class to use the same coordinate system as described in class. A new version of the framework code is available above, but you can download the single Camera.java file here.
• 11:00 am, 11 September 2005: I realize that I made a mistake in my solution ray tracer regarding the image orientation. Java's image API measures image coordinates from the upper left hand corner while the assignment measures from the lower right. To display the viewer and to write the images, the ray tracer uses the same data arrays that back the ray1 style images to create Java images, but since the origin is interpreted differently this operation causes Java to interpret the images as upside down. For practical reasons, reordering all the pixels per viewer update would take too long. The best thing to do is for you to flip your images over. This can be done trivially by fliping the camera orientation. If you have a working camera expect for upside down images, just negate the up vector at the end of the lookAt() method. I didn't check, but this might induce a mirroring of the image left to right so you might also have to negate the right vector for similar reasons. I also emphasize that image orientation will not count against you. So if you don't want to worry about flipped images you don't have to, but the fix is only one line.
• 11:00 am, 11 September 2005: There have been several questions about how mesh vertices are represented in the MeshTriangle structure and my documentation about this issue is scant. The Mesh structure packs all the data about the entire mesh in long float arrays. For this assignment you only need to access the vertex one. The vertex data is packed like this in that array: x0, y0, z0, x1, y1, z1, x2, y2, z3, ... where x0, y0, and z0 are the coordinates of the first vertex and so forth. Each MeshTriangle contains the three indices into this list. Using an index i, the positions of its vertex coordinates are: X = 3*i, Y = 3*i+1, Z = 3*i +2.
• 10:45 am, 12 September 2005: One of you pointed out that there is a better solution to the upside down image problem than negating the camera's up vector. You can change the ray1 image class' indexing scheme with a one line change. Go to misc.Image.java and find the method calcIdx(). Change its one line body from:

  return (inY * width + inX) * 3;

  to

  return ((height - 1 - inY) * width + inX) * 3;

  This will flip all images upside down. I was unhappy with the previous fix because it tied the construction of the camera basis to a particular image format, but I thought it was the only quick fix I could post. If you have already fixed the problem, feel free to change to this solution if you like it better or not. Again your image orientation will not affect the grade, so any way you want to fix this problem (or even not fix it) is fine with us.