CIS681 Lab 4

Images

Objective

Assignment

• Modify your ray tracer to incorporate new effects. Build a ray tracer which reads a scene description file of transformed (including non-uniform scale) spheres and cubes and writes a portable pixmap file (.ppm file) of the ray-traced scene.
• The raytracer should display at least one type of solid texture and one type of surface texture. Solid or surface texture should be on a sphere while the other type of texture should be on a cuboid - your choice which way to do it.
• You can use either procedural textures or table-based textures. You can hardcode this into your program. For example, all spheres get a stripe solid texture ; all cubes get a sinusoidal 2D texture on each face.
• Call your program lab4. As before, your program should take an argument of a scene description filename.
• Allow for non-uniform scaling by computing intersections in object space.
• Implement a ray-box intersection routine for ray tracing boxes. Calculate ray-axis-aligned-unit-cube intersections in object space. The cube command is simply:

  cube <r> <g> <b> <kd> <ks> <n> <kt> <n1>
  

• Also, note that the scale command should now accomodate non-uniform scale:

  scale <x> <y> <z>
  

• Include with your submission a sample scene file which contains a scene with:
  • a camera,
  • at least two lights, and
  • approximately 5 objects, including at least:
    • one transformed (including non-uniform scale) textured ellipse,
    • one transformed (including non-uniform scale) textured cuboid
  • include at least one solid texture and one surface texture

Notes

• As with previous labs, the lab will be graded on UNIX using your submitted makefile and input files that produce .ppm files that can be converted to .jpg and viewed using display. The grader should be able to do the following on the Department's UNIX system, assuming your input file is called input.txt and it outputs an image in output.ppm:

  make
  lab4 input.txt
  convert output.ppm output.jpg
  display output.jpg
  

• NEW: include a README.txt explaining the solid and surface texture functions you used.
• You do not need to include any reflection or refraction, but you should still have shadows
• You need to do the inverse transform back into object space of intersection points. Incrementally build up the inverse transformation matrix as you incrementally build the current transform matrix. Pseudo-code for display procedure looks like (skipping over some details):

    for each pixel
      form ray
      for each object
        inverse transform ray (source point and direction) into object space
        if (intersection of ray and object exists)
          if (closest intersection so far) 
            transform point and normal back into world space
            record object, object space point, world point, world normal
      if closest object is textured
        get texture color from object, texture and object space point
      do illumination model using color, world point, world normal
      record pixel color
  

• For non-uniform scale as well as textures, you need to inverse transform rays back into object space for the intersection computation.
• For the solid texture, just take the intersection point x,y,z through some procedure or table look-up (with interpolation) to get the new color.
• For the surface texture:
  • If the surface texture is on the sphere, then you need the inverse tangent function to map an x,y,z intersection location to u,v coordinates
  • If the surface texture is on the cube, then you find the last entering face and map the x-y, y-z, or x-z coordinates (depending on which plane its on) to u,v simply by adding 0.5 to each.

Extra Credit

• Generate a nice-looking wood texture
• Generate a multiple frequency marble texture
• Do some kind of interesting 2D table-based texturing
• Genrate an interesting and/or complex scene including reflection and refraction