trace spheres.iv' will load spheres.iv. The trace
program is paused when it begins, so to start tracing the scene,
select "Continue" from the "Trace" menu. The spheres in the scene
should appear as flat disks, since the routines that compute the
color of each pixel have been gutted for your educational benefit.There are several inventor models located in /cse/courses/cse457/models/. To create or alter scenes, you may use a text editor or a modified version of 'SceneViewer', an Inventor demo program. The modifications allow you to save the lights and camera in a scene file, set an object's reflection and refraction, and run the trace program on the current scene by selecting a menu item. Be warned: a few bugs in SceneViewer have been fixed, but several still remain. The SceneViewer program is located in /cse/courses/cse457/bin/SceneViewer, and the source code is in /cse/courses/cse457/src/SceneViewer/. You may change the options SceneViewer gives to the trace program by adding a line to either your .Xdefaults or .Xresources file, such as the following (note the '-' at the end):
SceneViewer*trace: /homes/isgi/zhuw/457/trace/trace -s 640x480 -m -
The syntax and meaning of the trace program's command line options can
be displayed with the -h option:
Trace Inventor ray tracer, version 0.0
Usage: trace [options] [SceneFile.iv]
options: - Read scene from stdin
-d# Set maximum levels of ray recursion
-r# Set minimum ray contribution (float) for recursion
-c Command line only (no window)
-m Mesh image
-q# Set image quality
-s#x# Set image size to width x height
-ofile Output resulting image to file
One such option, -m, tells the trace program to represent
the image as a triangulated mesh rather than a bitmap. The mesh
allows for a progressive adaptive refinement of the image and permits
the user to better zoom and pan. To pan the image interactively,
left-click on the image and drag the mouse, or to zoom, middle-click
and drag.
Another option, -s WidthxHeight, allows the size of the
output image to be set. You will probably want to speed-up your
traces by setting the size of the bitmap to something small, say
50x50, rather than the default of 320x200. Also, a menu option alows
you to resize the image as well, Image/Resize Image....
The command line option specifying an output file allows you to render
images off-line. That is you can run trace as a background task, log
off, and the trace will proceed until the image completes. Please
be considerate when rendering off-line images by using the unix
commands nice (run the task at a lower priority) and
at (specify some later time for the task to start
running) (See the man pages for details.)
RayTrace.{c++,h} here's where all the required extensions will be added
RayCast.{c++,h} if you are implementing the RayIntersection routines
they'll go here.trace.{c++,h} bells & whistles such as adaptive antialiasing, distributed
raytracing, and stereogram generation can be implemented in the trace()
procedure. Here also is defined the RayInfo structure.
SuperState.{c++,h} these define the scene graph super state nodes,
you shouldn't have to make changes here.Util.{c++,h} you probably won't need to touch these either,
but here's where
the global scene and image structures (SceneInfo, ImgInfo, are defined
here, as well as structures that hold ray intersection
data (RayCastInfo, and IS).
ui.{c++,h} you will have to make changes here and to
trace.uil for any user-interface modifications you'll make.trace.uil this is a User Interface Language file that gets
compiled with the uil unix command. Basically, in it are
definitions for all of the motif widgets of the user interface. (See
man pages on uil for details.)
SbColor Raytrace(SceneInfo *sceneInfo, RayInfo *rayInfo);This function calculates the color of a ray that is cast into the scene. Refer to your handout for the pseudo-code of a ray-tracing implementation.
typedef struct
{
SbVec3f startPos;
SbVec3f vecDir;
long depth;
float contrib;
} RayInfo;
The fields vecDir
and startPos indicate the ray's direction and origin, respectively.
Also in the structure is a depth field which holds the current level
in RayTrace()
(e.g.,. initial rays have depth 0, spawned rays have depths > 0). Similarly, the
contrib field holds how much (multiplicative) contribution a ray has
to a pixel's color value.
typedef struct
{
SoSeparator *root;
SoGroup *lights;
SoEnvironment *env;
SoCamera *camera;
Options *options;
GroupStack *seps;
RayCastInfo rayCastInfo;
} SceneInfo;
The options field is explained below. The camera is used to
calculate the initial rays from the eye point; this is done for you by
the routine that calls RayTrace(). The env(ironment) field points to
a SoEnvironment node, which stores the global ambient color, the
attenuation, and the fog color, (in case you want to add them).
The lights field is a pointer to a SoGroup node containing a list of
lights, which can be a
mixture of SoDirectionLight, SoPointLight, and SoSpotLight. To get the
ith light or find how many lights there are, see the SoGroup (x)man page.
The routines for SoGroup will return a pointer to a generic node, so
you will need to find out what type of light it is and cast the pointer
returned into a node of that type. To determine which type of light it
is, you should call something like
isOfType(SoPointLight::getClassTypeId())
in C++ or SoNodeIsOfType(light, SoPtLtGetClassTypeId())
in C. The root
field points to the root of the scene graph, and you will want to apply
SoRayPickAction to it.
typedef struct
{
SuperState *superState;
SbVec3f pickedPoint;
SbVec3f normal;
SbVec4f texCoords;
int materialIndex;
} IS;
These fields names are pretty much self explanatory. Note that you
will want to flip the surface normal when computing Phong illumination
if the angle between it and the ray direction exceeds 90 degrees.
Inventor has facilities to create, view, and manipulate scenes of three dimensional objects. These scenes are represented by directed graphs of nodes. The nodes fall into several categories: some are basic shapes (cube, sphere, cone, mesh, spline surface); some describe the attributes of a shape (color, transparency, control points to use), some are transformations (rotate, translate, scale); some (called group nodes) contain lists of pointers to other nodes, and there are many others. One node is at the root of a scene graph, from which every other node in the graph is descended. Cycles in the graphs are not permitted.
There are several actions that may be applied to a scene graph, such as rendering the scene with OpenGL, writing the graph to a file, searching for particular nodes, finding a bounding box, and picking the nodes that are intersected by a given ray. These actions typically traverse a scene graph from the top (root) down, going left to right within each group node. In many cases, a state is kept during traversal. For example, when finding nodes that are intersected by a ray, the current transformation matrix must be calculated -- otherwise when Inventor tried to determine whether some object in the graph was intersected, it wouldn't know where the object was positioned in space.
NOTE: You may find additional information in the online book
/usr/share/src/Inventor, and a few executable Inventor
programs are in /usr/sbin/iv*.
typedef struct
{
char sceneFilename[MAXPATHLEN + 1];
char bitmapFilename[MAXPATHLEN + 1];
SbVec2s bitmapSize;
unsigned maxRayDepth; // Recurse at most this deep in RayTrace()
float minRayContrib; // Recurse in RayTrace() when ray's contrib is no less this
SbBool interactive; // Want windows?
SbBool outlines; // Draw mesh triangles with outlines
SbBool antialias;
unsigned quality; // Exact meaning undefined
ImgMode imgMode;
} Options;
Options.c contains a couple functions to parse and display usage for
the command line options. This structure should not be needed for the
required part of the assignment.