Oni Central Forum

A Community-driven Forum discussing Bungie's Oni

You are not logged in.

#1 4/10/11 12:59

Bozzman
Member

Phoenix Engine - 3D Reference Guide

For those who are thinking about modding Overgrowth for potential Oni projects this was a post over on the WolfireForum concerning some details of model formats and such - I understand some of it (not all of course) but here's a look into what you would be dealing with. If you see something you could do here, I would encourage you to purchase the Alpha and experience the progress they're making first hand. And spread the word! Word of mouth is what is making this game grow!

Basics

In Overgrowth 3D models use the .OBJ format but the material counter-part (.MTL) is not used, instead an “object properties file” stores links to model and texture files as well as some other information. This is the file you choose when loading an object, it uses the .XML format and can be read/created in any text editor:

ObjectPropertiesFile.jpg
object properties file

Tags:
<Model> - links to the model file (.OBJ)
<ColorMap> - links to the color texture file (.TGA .TIF)
<NormalMap> - links to the normal map texture file (.TGA .TIF)
<ShaderName> - refers to internal shader file (.FRAG .VERT), defines how object is rendered.
<MaterialPath> - links to internal material file (.XML), defines sound made by hitting the object.
Additional tags:
<flags no_collision> - turns physics calculations on/off, true = off.

“<ShaderName>” used to be “<ShaderPath>” and contained the full link instead of just the file name, expect similar update for “<MaterialPath>”.

Look at the example plant object for usage of the <flags no_collision> tag.

Model and Texture Requirements
Models need to be constructed from squares and triangles only, textures need to be square and not just “powers of 2”. (512x512 or 1024x1024 not 512x1024 or 1024x2048)

SimpleObject.jpg
Simple object and texture UV layout



____________________________________________________________________________________

Alternative object System

The engine automatically generates a simplified physics object and uses the object’s UV layout to place the shadow maps, these can be overridden by providing alternative .OBJ files that contain the desired information. These objects are placed in the same folder and share the same name as the original .OBJ file with a suffix to tell the engine what data they hold:

Suffixes:
YourObject_COL.obj - contains simplified geometry for physics calculations
YourObject.obj_UV2     - contains same object but with no overlapping UVs
YourObjectHULL.obj - same as _COL but has extra info, used with weapons

The suffix formats are inconsistent, _COL is placed before the file extension while _UV2 is place after, and HULL doesn’t even have an underscore to separate it from the file name!

Physics objects (_COL)
Simplified geometry such as boxes an cylinders which are used for collision detection, they are aligned to your object based on “relative position” in your 3D program so you should place the physics mesh on top of your render mesh upon export:

PhysicsObject.jpg
Physics mesh should be placed on top of the render mesh

Shadow UV objects (_UV2)
These objects tell the engine how to place the shadow map on the rendered object if the original UV layout isn’t appropriate, the shadow maps require UV layouts with no over-lapping faces, this can usually be achieved using the “automatic unwrapping” tools found in most 3D applications.

UVObject.jpg
Color texture UVs left, shadow UVs right, each face needs its own UV space.

Hull objects (HULL)
They are very similar to physics objects but are used for items and weapons, the only difference is that they contain a free-floating triangle which defines the object’s center of gravity.

HullObject.jpg
Hull objects are placed over render mesh like physics objects.



____________________________________________________________________________________

Items and Weapons

Items and Weapons are aligned to the character based on their position relative to the center of the scene in your 3D app, you should load the .obj files of the example objects for reference. To make an object “pick-up-able” you need another .XML file that you load in place of the regular object properties file, it stores the info needed that is not defined in the regular object properties file:

ItemPropertiesFile.jpg
Item properties file

Tags:
<type> - defines what type of item the object is.
<appearance obj_path> - links to the regular object definition file.
<grip ik_attach anim> - defines what bone the object is attached to, links to an animation file.
<physics mass> - changes the pitch(?) of the sound made by the object hitting things
<anim_override idle> - overrides the idle animation of a character holding the item.

Not sure what the animation file in <grip ik_attach anim> does.

<anim_override idle> is only used for 2-handed weapons at the moment.

Weapons.jpg
Example weapons, handles show the location of characters hands

There is a bug that makes weapons turn invisible when loading levels with them already in it, you can fix this by having the “regular-object" version somewhere in the level as well.


____________________________________________________________________________________

Shaders

Cubemap – closest thing to a “standard shader” at the moment, it has a cube-map based on the sky texture and a specular shine, the visibility of the cube map and shine is controlled with color texture’s alpha channel, white = fully reflective and shiny.

The cube map’s visibility is inversely affected by the brightness of diffused light on an object so you should make the color texture black for materials that reflect no diffused light such as chrome and glass.

CubemapObj - same as Cubemap but uses object-space normal maps instead of tangent space.

CubemapItem – same as Cubemap but the shine is sharper.

CubemapObjItem – object-space version of CubemapItem.

CubemapAlpha – has transparency controlled by the color texture’s alpha channel, cube map and shine are controlled by the normal-map texture’s alpha channel instead.

CubemapAlpha has depth sorting issues with other transparent objects, enabling anti-aliasing fixes this somewhat.

CubemapObjChar – used for characters, shine is sharp, uses object space normals.

There is no tangent-space version of CubemapObjChar and no object-space version of CubemapAlpha at the moment.

Plant – has transparency like CubemapAlpha but no cube map/shine. Translucency texture increases the brightness of the object while ignoring diffuse lighting, black = no effect. Wind texture defines intensity of a vertex ripple effect, black = no ripple. Both textures are linked in the object definition file using the <TranslucencyMap> and <WindMap> tags.

CubemapAlpha.jpg
CubemapAlpha

Translucency.jpg
Translucency



____________________________________________________________________________________

Materials

These are the sounds made and the particles emitted when you hit an object. I’ve set up some tiles for you to walk on to preview each material, here is a list:

Cloth_Fabric
Cloth_Leather
Default
Dirt
DirtyRock
Drygrass
Grass
Gravel
Rock
Rocks
Sand
Snow
Wood

Materials.jpg
“Sound tiles”

Some of these don’t emit particles.


Here take this hypo!

Offline

#2 6/10/11 21:49

EdT
Moderator

Re: Phoenix Engine - 3D Reference Guide

Thanks for the guide.  Did you pre-order Overgrowth?

Offline

#3 6/10/11 23:03

Bozzman
Member

Re: Phoenix Engine - 3D Reference Guide

Yes I have - I'm truly excited for it. And this "guide" isnt complete of course but if I see any more posts relating to potential modding ill be sure to share them (within reason I can't spill everything since it is technically a secret preorder forum)


Here take this hypo!

Offline

#4 6/10/11 23:52

EdT
Moderator

Re: Phoenix Engine - 3D Reference Guide

It sounds very interesting, have you made any mods for it? if so, are you allowed to show them outside the secret forum?

Offline

#5 7/10/11 8:15

Bozzman
Member

Re: Phoenix Engine - 3D Reference Guide

Haha noooo, not yet. They need to make a more baseline guide for me. I'm not even sure where to start! I do know that people have made new player characters - now i just need to find out how.


Here take this hypo!

Offline

Board footer