Hello,

Can anyone explain the material property mapping used to export x3d scenes.

The writeMaterial function tweaks blender material properties a lot before exporting them and these tweaks cannot be inverted.

export_x3d.py :

Code:

def writeMaterial(ident, material, world):         material_id = quoteattr(unique_name(material, MA_ + material.name, uuid_cache_material, clean_func=clean_def, sep="_"))         # look up material name, use it if available         if material.tag:             fw('%s<Material USE=%s />\n' % (ident, material_id))         else:             material.tag = True             emit = material.emit             ambient = material.ambient / 3.0             diffuseColor = material.diffuse_color[:]             if world:                 ambiColor = ((material.ambient * 2.0) * world.ambient_color)[:]             else:                 ambiColor = 0.0, 0.0, 0.0             emitColor = tuple(((c * emit) + ambiColor[i]) / 2.0 for i, c in enumerate(diffuseColor))             shininess = material.specular_hardness / 512.0             specColor = tuple((c + 0.001) / (1.25 / (material.specular_intensity + 0.001)) for c in material.specular_color)             transp = 1.0 - material.alpha             if material.use_shadeless:                 ambient = 1.0                 shininess = 0.0                 specColor = emitColor = diffuseColor             ident_step = ident + (' ' * (-len(ident) + \             fw('%s<Material ' % ident)))             fw('DEF=%s\n' % material_id)             fw(ident_step + 'diffuseColor="%.3f %.3f %.3f"\n' % clamp_color(diffuseColor))             fw(ident_step + 'specularColor="%.3f %.3f %.3f"\n' % clamp_color(specColor))             fw(ident_step + 'emissiveColor="%.3f %.3f %.3f"\n' % clamp_color(emitColor))             fw(ident_step + 'ambientIntensity="%.3f"\n' % ambient)             fw(ident_step + 'shininess="%.3f"\n' % shininess)             fw(ident_step + 'transparency="%s"\n' % transp)             fw(ident_step + '/>\n')

Thank's

Not sure what you are referring to specifically, but I suspect the 'tweaks' are to translate from one set of metaphors to another.

The main issue with import/export is not converting the numbers, but translating from the way one program looks at the world to another's view. Examples might be simple, like converting from Z pointing up to Z pointing into the screen. A more complex example might be converting from Blender's view of Materials and Textures being separate entities to one where Material encapsulates both concepts.

My main problem is I can't reproduce blender rendering using data from x3d export.

X3D specification doesn't suggest these tweaks are required and I think there are wrong. However I'm not a blender specialist and maybe I'm misunderstanding something.

http://www.web3d.org/files/specifications/19775-1/V3.2/Part01/components/lighting.html#Lightingmodel

X3D just uses a standard Blinn model with light attenuation and Blender seems to use the exact same one (if we configure materials with Lambert+Blinn).

The most disturbing parts of writeMaterial are the emissive color and the specular color :

Code:

emitColor = tuple(((c * emit) + ambiColor[i]) / 2.0 for i, c in enumerate(diffuseColor))

Code:

specColor = tuple((c + 0.001) / (1.25 / (material.specular_intensity + 0.001)) for c in material.specular_color)

Why not :

Code:

emitColor = emit * diffuseColor

Code:

specColor = material.specular_color * material.specular_intensity

Should I move this question in another section ?

i don't think that's a problem, rather no one can give you an answer. Maybe try to find a dev who knows (probably ideasman42) on IRC, freenode.net #blendercoders
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CoDEmanX wrote:

i don't think that's a problem, rather no one can give you an answer. Maybe try to find a dev who knows (probably ideasman42) on IRC, freenode.net #blendercoders

Thank's !