RTObject.h includes three
basic classes：RTObject,
HitStructure, BBox. I combined Triangle and Sphere into one
class--RTObject, based on the following considerations:
a. Sphere class has two
basic properties (sphere center and radius), whereas, Triangle class
has three points(points are float3 type, radius is float type)
b. In CUDA, it's not
like C++ has complete class hierarchy, which means you can’t have
a super class which does not contain anything and its two subclasses
containing their own data. CUDA cannot figure out what the super
class points to in running time. This is my supposition
c. In my RTObject there
are four basic properties (three float3 data (points) and a float
data(radius)). If a RTObject is a triangle, I ignore the radius, and
if it's a sphere I ignore two points and let the left point be the
sphere center. It may waste a lot of memory space for a scene full of
many spheres, However I believe that a normal scene contains only a
few spheres which may waste a little memory space three basic classes
, whereas, triangles are the basic elements of meshes or complicated
scenes, for the meshes, only radius data are useless(4 bytes), which
is a kind of trade off between complexity design and a little
overusing memory.
In Ray.h, I normalize
every type of ray whenever created except the shadow ray. Each ray
maintains its own tmin and tmax for the intersection test. tmax will
be changed only if the intersection condition is satisfied, which is
the criterion of intersection test.
In Mesh.h, technically
it is supposed to have a pointer to a triangle list and a pointer to its
BVH list. However on normal Nvidia devices, CUDA does not support
deep copy (when you copy the data of Mesh class, it does not copy the
data its data members(pointers) point to). Instead I use index tokens
to mark the triangle list and BVH list. When you copy mesh lists, as
well as the triangle lists and the BVH lists their tokens point to .
In BVH.h, building BVH is
only based on the information of AABB (axis aligned bounding box) of
all objects in the scene. I put the whole built BVH into BVH array .
a. Find the mid point of
the current part of the BBoxes Array
b. Use spatial median
cut
c. Store the start,
median, and end position of the BBoxes Array,
let the start position be
the start position of subarray1 (which still is inside of BBoxes
Array), just as if it’s independent)
let the median
position be the end position of subarray1
let the median
position be thestart position of subarray2
let the end
position be the end position of subarray2
d. goto a;
