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:
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>”.
Model and Texture RequirementsLook at the example plant object for usage of the <flags no_collision> tag.
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)
Simple object and texture UV layout
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Collision/Physics Objects
The engine automatically generates a simplified physics object from your model but this can be overridden by providing an alternative .OBJ file. The file is placed in the same folder and shares the same name as the original .OBJ file with a suffix:
Suffixes:
YourObject_COL.obj - contains simplified geometry for physics calculations
YourObjectHULL.obj - same as _COL but has extra info, used with weapons
Collision objects (_COL)inconsistent, HULL doesn’t have an underscore to separate it from the file name!
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:
Physics mesh should be placed on top of the render mesh
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.
Hull objects are placed over render mesh like physics objects.
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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:
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.
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.
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Shaders
Cubemap – closest thing to a “standard shader”, 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. Similarly, the normal-map texture’s alpha channel controls where color tinting happens, white = full effect.
CubemapObj - same as Cubemap but uses object-space normal maps instead of tangent space.The cube map’s visibility is inversely affected by the brightness of the texture, you should make the color texture close to black for materials that are reflective such as chrome and glass.
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.
CubemapObjChar – used for characters, shine is sharp, uses object space normals.CubemapAlpha has depth sorting issues with other transparent objects, enabling anti-aliasing fixes this somewhat
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.There is no tangent-space version of CubemapObjChar and no object-space version of CubemapAlpha at the moment.
CubemapAlpha
Translucency (Plant Shader)
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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
“Sound tiles”
Some of these don’t emit particles.