Kdtree-model-import
From Manta
NOTE: This part of the repository has been deprecated and the DynBVH has replaced the kd-tree as the primary acceleration structure.
See Triangle Scene Viewer for instructions to load .obj or .ply files.
The kd-tree code and Fox GUI, associated with the original 2006 work with SGI & Boeing has been moved to: https://code.sci.utah.edu/svn/people/abe/code/Manta-Fox/ See: Build instructions for Manta-Fox
| Table of contents |
Importing Models into Manta
This page describes how to convert a model into the .v3c1* format used for the Boeing 777 demo dataset.
This page does not describe how to import general models into other acceleration structures.
File Formats
.v3c1 is a collection of simple binary file formats used by Manta. The binary files are always assumed to be in little-endian byte order and are automatically converted by the loader to the native byte order.
| Required files. | |
| file.v3c1 | Triangle file each triangle is 9 floats for vertices followed by a three float color. This may be generated manually or using bin/v3c1_tools. |
| file.v3c1.kd | Direct binary serialization of kdtree using struct format in KDTree.h |
| file.v3c1.id | Unsigned integer offsets used by kdtree. |
| Optional files. | |
| file.v3c1.tex2 | 2D texture coordinates, 6 floats for each face. |
| file.v3c1.nor | Per vertex normals, 9 floats for each face. |
| file.v3c1.grp | Offsets into the name file for each face. |
| file.v3c1.nam | Null terminated strings for each group name. |
The repository contains a utility, bin/v3c1_tools, for creating and managing .v3c1 files.
v3c1_tools
The bin/v3c1_tools program started out as a simple program to convert the Double Eagle tanker dataset to the v3c1 binary triangle format in order to run a kdtree builder on the data. Since then it has balloned into doing much more.
Command line Options
As of r931 the options are:
bin/v3c1_tools
Usage: v3c1_tools -vn3 -in <tanker paths...> -out <outfile.v3c1>
v3c1_tools -obj -in <file1.obj ...> [-out <outfile.v3c1>]
Related options: (might not work with other conversions)
-scale <x> <y> <z> -- Scale the model before writting
-normals -- Output a vertex normal file.
-flip -- Use glm to reverse winding direction.
-vertex_normals <d> -- Use glm to compute vertex normals using
the specified angle threshold (in degrees)
-texcoords -- Output a vertex texture file.
-loud -- Print per group info.
v3c1_tools -m -in <file1.m ...> -color <r> <g> <b> [-out <outfile.v3c1>]
Hughes Hoppe .m file format conversion.
v3c1_tools -info <infile.v3c1 ...>
Computes bounds and number of triangles, colors.
v3c1_tools -clip <px> <py> <pz> <nx> <ny> <nz>
Apply a clipping plane to the input files given a point and normal.
v3c1_tools -scale <x> <y> <z>
Scale the input v3c1 file and write to the output file.
Outfile optional uses group names otherwise.
These options can be divided into two categories, those for converting meshes to .v3c1 triangle soups and those for maniuplating .v3c1 files.
Nate Robin's GLM (heavily modified) is used to load .obj files.
Usual workflow
Most small models can be converted to .v3c1 from .obj using the utility and then kdtrees can be generated for them. Special scripts or small Performer programs were written for special cases like the Boeing 777 dataset.
Converting a .obj file
For this example I'll use a variation on my favorite model, my toy truck (http://www.sci.utah.edu/%7Eabe/cs6620-raytracing/project11/index.html).
This is an .obj file which I exported from Blender along with a .mtl file.
ls -l total 16848 -rwxr-xr-x 1 abe sci 1456 2006-02-16 00:41 defender-final-truck.mtl -rwxr-xr-x 1 abe sci 17228419 2006-02-16 00:41 defender-final-truck.obj
The simplest way to just get the data in a form that you can load it is to convert only the mesh itself:
v3c1_tools -obj -in defender-final-truck.obj -out defender-final-truck.v3c1 Bounds: -7.96389 -8.57825 0.0496373 4.5816 5.04275 10.3117
Building the kdtree
Unfortunately, the only kdtree building tool for manta isn't in the repository. It can be downloaded in binary form for ia64 and em64t.
There are both single processor and parallel build programs available.
kdbuild.seq defender-final-truck.v3c1 0.99
Reading in defender-final-truck.v3c1 (59792 triangles). . .0.01 secs
checking for NaNs...OK!
Building kdtree:
ChildParentCostRatio=0.99 MaxSizeToSlowSplit=59792 FracOfParentVolToSplit=0.10
BuildTree time 15.01 secs
NumNodes 1778116
MaxDepth 91
NumLeaves 474082
NumTrisInLeaves 1141200
MaxInLeaf 50
MinInLeaf 1
AvgInLeaf 2.4
Creating [defender-final-truck.v3c1.kd]
[defender-final-truck.v3c1.idx]
It is possible to build a better kd tree for this model by manipulating the command line parameters.
Then run the model using:
bin/dm_demo -np 4 -scene "lib/libscene_boeing777.so( -file defender-final-truck.v3c1 )" -camera auto Using 4 workers plus one gui thread. Cannot open file: defender-final-truck.v3c1.nor Using per triangle normals Cannot open file: defender-final-truck.v3c1.tex2 Not using texture coordinates. Time to input triangles: 0.007125 seconds. Total file size: 2.73706 MB. IO Performance: 384.149 MB/second. Please wait... Time to read kdtree: 0.028485 seconds. Model bounds: min: -7.9639 -8.57825 0.0496323 max: 4.58161 5.04276 10.3117 Total time to read in indices: 0.006319 start loading grp defender-final-truck.v3c1.grp WARNING: cannot open .grp file; picking disabled Total load time: 0.00126427 minutes. Auto camera: pinhole( -eye -1.69114 19.4037 5.18069 -lookat -1.69114 -1.76775 5.18069 -up 0 0 1 -fov 60 ) Building transparent tree.
