Ray Tracing, Version 3.1
Day #6

Goal: Ray trace a scene where

  • the only objects in the scene are generic spheres, planes, squares, and tapered cylinders
  • the objects may have been translated, scaled, and/or rotated with respect to an axis
  • in addition to color, the attributes of each object may include material coefficients for diffuse, specular, ambient color
  • a positional light may be placed in the scene
  • the light has a diffuse, specular, and ambient component
  • a value for global ambient light may be assigned
  • shadows are correctly rendered
  • descriptions of the objects, lights, and camera are read in from a file, using SDL

Scene Class:

At this point you will probably want to take all of your ray tracing functions in your driver program and make them methods of a new class, Scene. This class should be kept in a separate file, scene.h and scene.cpp. You will need to change your makefile to reflect this. The necessary global variables that you have in your driver program will now become data members of the Scene class. The functions in your driver program pertaining to ray tracing will now become method members of the Scene class. Those functions are: readScene, rayTracer, getFirstHit, shadePixel, and shade. Your driver program will be very simple now. Before adding anything new to your ray tracer, make this change and verify that your program still works correctly.

Ray Tracing Tools:

Add the following data fields to class hitInfo:

int surface;           //which surface was hit
bool isEntering;  //is ray entering the object?
     

and change Sphere::hit( ) so that it records values for these two new fields. Surface is 0 for both sphere hits; the first hit is entering the sphere but the second hit is not.

Add these new classes: Plane, TaperedCylinder, Square. Like the Sphere class, each of these generic object classes will have one method: hit. Be sure to test each before entrusting it to your ray tracer.

Add Method to Scene Class:

Add a new method to Scene,

       bool isInShadow(Ray3D shadow_feeler);

which goes through the object list looking for a hit; if one is found it returns true, else it returns false. It does not keep any any information about the hit -- we are only interested in whether or not there was one. The precondition for this methods is that shadow_feeler is the ray starting from a point slightly offset from the hit point on the object, going in the direction toward the light source.

ReadScene:

As you add each new generic object to your ray tracer, the readScene method needs to be updated to reflect this.


Test Files:

The test file shadow.scn is available to test the shadow method.

All files are located in /classes/cs3114/Advanced_Graphics/files directory