19czepeda / miniscene

miniScene

A mini-app like scene graph with binary reader/writer. Has a simple material model, one level of instances, and objects with one or more triangle meshes. Comes with several importers/converters, but can be built with only minimal dependencies.

Dependencies

Currently this projects builds on top of OWL (for the convenience of the OWL vector/math library, and for a sample model viewer for miniScene models that this project contains). This means this project currently does depend on:

• OptiX (7.0 or newer)
• CUDA (11.0 or newer)

This project also uses several other libraries that it pulls in via submodules.

Importing Scenes - Examples

"Importing" for this library means that there's a tool(-chain) involved in converting from another scene/model format to our mini format.

Some common/useful examples:

PBRT v3 landscape model

This uses the pbrtParser submodule to first convert from .pbrt to that pbrtParser's pre-parsed binary-pbrt .pbf format, then converts from that to mini:

	./pbrt2pdf -o /tmp/landscape.pbf ~/models/pbrt-v3-scenes/landscape/view-0.pbrt
	./pbf2mini -o landscape.mini /tmp/landscape.pbf -t ~/models/pbrt-v3-scenes/landscape
	./miniInfo landscape.mini

• Make sure to pass the -t <texturepath> during the pbf2mini conversion; pbf only stores the relative filename, and without that textutes cannot be included.

After that you should see this

#miniInfo: scene loaded.
----
num instances		:   30.03K	(30035)
num objects		:   29
----
num *unique* meshes	:   370
num *unique* triangles	:   27.78M	(27783147)
num *unique* vertices	:   24.56M	(24558785)
----
num *actual* meshes	:   407.69K	(407691)
num *actual* triangles	:   4.35G	(4349699001)
num *actual* vertices	:   3.25G	(3253912887)
----
num textures		:   156
 - num *ptex* textures	:   0
 - num *image* textures	:   157
total size of textures	:   498.06M	(498064452)
 - #bytes in ptex	:   0
 - #byte in texels	:   498.06M	(498064452)
num materials		:   369
num quad lights		:   0
num dir lights		:   1
has env-map light?	: yes, with 512x256 texels

Moana Island, including baking of PTex Textures

One of the reasons I developed this library was that I needed to be able to parse certain PBRT-formated files --- in particular, the PBRT landscape and Disney island (aka Moana) model --- into my own renderers. In particular for island, that also required deadling with the PTex textures that the model comes with, but which aren't easily supported on GPUs. To handle those, this library contains a ptex 'baking' tool that bakes these textures into a texture (a texture atlas, to be exact) such that every patch in the input mesh gets NxN bilinearly interpolated texels assigned to it (with N being a cmdline argumnet).

To do this conversion and baking step:

• first, download moana, using the base and PBRT packages, as well as textures

• second, convert island.pbrt to pbf using the pbrt2pbf tool that comes with this library. This is a "binary" version of that model in the pbrtParser format (but still contains many unparsed things like ptx texture names as plain filenames)

./pbrt2pbf ~/models/island/pbrt/mountains.pbrt -o /tmp/mountain.pbf

• third, convert the file to 'mini', with embedding (but not yet baked ptex). In this version of the model all the ptex binary data is directly embedded in the mini file, but still in ptex format

./pbf2mini /tmp/mountain.pbf -o /tmp/mountain-embedded.mini -t ~/models/island/textures/

• finally, use the mini ptex baking tool to bake the ptex into regular NxN per patch textures. This assumes that the meshes with ptex on them actually use two triangles per quad - as is the case for the disney island model, but maybe not for all ptex based models. This baking step will bake the ptex into regular textures, and add appropriate texture coordinates to the triangle mesh(es) that use those textures. Note this will increase the size of the model since the vertices with baked texture atlas coordinates will no longer be sharable across neighboring triangles.

./miniBakePtex /tmp/mountain-embedded.mini --res 16 -o mountain.mini

This final mountain.mini file should be a model that contains only triangle meshes with 'plain' textures on them. E.g.:

 wald@vk:~/Projects/miniScene/bin$ ./miniInfo ./mountain.mini 
loading mini file from ./mountain.mini
#miniInfo: scene loaded.
----
num instances		:   1.14M	(1135547)
num objects		:   36
----
num *unique* meshes	:   2.37K	(2368)
num *unique* triangles	:   14.38M	(14380782)
num *unique* vertices	:   28.76M	(28761564)
----
num *actual* meshes	:   2.36M	(2356231)
num *actual* triangles	:   13.54G	(13537454354)
num *actual* vertices	:   27.07G	(27074908708)
----
num textures		:   8
 - num *ptex* textures	:   0
 - num *image* textures	:   9
total size of textures	:   110.10M	(110100480)
 - #bytes in ptex	:   0
 - #byte in texels	:   110.10M	(110100480)
num materials		:   30
num quad lights		:   0
num dir lights		:   0
has env-map light?	: no

(note the main island model does have a env map, and is much larger; this is only the mountain geometry---I was running this on my laptop)

Stanford Model Repository: Atlas Model

The stanford model repo contains various laser-scanned status of various sizes; each in ply format, but some split across multiple files. The "atlas" model is one of the larger ones, and comes in 12 files that require some stitching.

Assuming you have the following directory downloaded from that archive:

wald@envy:~/Projects/miniScene/bin$ ll /space/atlas/
-rw-r--r-- 1 wald wald 308k Apr 15 13:16 atlas_qtrmm_10_11.matches
-rw-r--r-- 1 wald wald 446M Apr 15 13:15 atlas_qtrmm_10.ply.gz
-rw-r--r-- 1 wald wald 271k Apr 15 13:16 atlas_qtrmm_11_12.matches
-rw-r--r-- 1 wald wald 420M Apr 15 13:15 atlas_qtrmm_11.ply.gz
-rw-r--r-- 1 wald wald 289k Apr 15 13:15 atlas_qtrmm_1_2.matches
-rw-r--r-- 1 wald wald 241M Apr 15 13:16 atlas_qtrmm_12.ply.gz
(and a few more of that)

...then the import path for that is as follows:

gunzip /space/atlas/*.ply.gz
./ply2mini /space/atlas/atlas_qtrmm -o /space/atlas.mini --stanford-stitch 12

Notes:

• the --stanford-stitch 12 tells the ply reader that there's 12 individual files that require some stitching using the .matches files that come with some of these models
• this model is fairly large - you may want to run that on a machine with quite a bit of memory and swap space.
• the outcome of this should look like this

./miniInfo /space/atlas.mini 
loading mini file from /space/atlas.mini
#miniInfo: scene loaded.
----
num instances	    	:   1
num objects     		:   1
----
num *unique* meshes	:   12
num *unique* triangles	:   507.51M	(507512682)
num *unique* vertices	:   255.04M	(255035497)
----
num *actual* meshes	:   12
num *actual* triangles	:   507.51M	(507512682)
num *actual* vertices	:   255.04M	(255035497)