COLLADA Guide

In this guide, you will learn how you can export your model from your modeling software (3DS Max, Maya, or SketchUp) into a COLLADA file that can be used with Building Composer.

Contents

What is COLLADA?

COLLADA is an open standard which defines a file format for complex 3D objects, in this case, your building model. 3D geometry data can be exported to the COLLADA format from most modeling applications.

Before Exporting

Building Composer Data Flow


Building Composer expects every COLLADA file to contain only a single Level of the Building. Hence, divide your building into individual levels, and for each Level, export all of its objects into a single COLLADA file.

Tip: It is easier to divide your model into Levels earlier in your modeling process rather than later.

Tip: Do test exports of your scene. There are many quirks with COLLADA exporters which might cause your model to not export correctly when you use some particular feature of your modeling application. To avoid massive remodeling effort in the later stages, test your model often with Building Composer.

Note that Building Composer does not change your 3D objects. Your building model exported from Building Composer will remain similar visually, except that it has the added BBL information. Therefore, ensure that

Tip: You should keep the total triangle count of all the buildings in your scene below 500,000. Having too high triangle count will slow down the performance of GermaniumWeb, especially when running on lower end machines. Check out our Modeling for Real-Time 3D guide.

Exporting to COLLADA

Pick a COLLADA exporter for your modeling application. You can pick one COLLADA exporter from our list of recommended exporters or one that is supported by your application.

Generally, COLLADA exporters often provide some options to choose when exporting your model. COLLADA supports a wide range of 3D modeling features, such as geometry meshes, morphing, animation, physics, shaders and effects. However, only a subset of the features are supported by Building Composer.

Features support in Building Composer:

Note: Some exporters do not export some features such as instancing or double-sided materials. Our list of COLLADA exporters has some known issues about the COLLADA exporters we have worked with. You may need to experiment with your exporter settings. Post on the forum if you need assistance.

Troubleshooting the exported COLLADA file

Sometimes, Building Composer rejects your COLLADA file. In other cases, you find that your model does not look correct in GermaniumWeb, with missing textures and/or geometry. The reason may be that your COLLADA file is erroneous or incompatible with Building Composer.

Try these methods to verify that your COLLADA file is indeed valid.

Manually fixing the COLLADA file

Some issues with the COLLADA file can only be fixed by manually editing the file. A COLLADA file is simply a XML text file. You can edit the file by opening it in any text file editor such as WordPad.

Note: Be careful when editing the COLLADA file. Do not make changes to other parts of the file. Otherwise, your COLLADA file may become invalid.

Checking the version of a COLLADA file

The version of the COLLADA file can be found on the second line of the COLLADA file.

<COLLADA xmlns="http://www.collada.org/2005/11/COLLADASchema" version="1.4.1">

Specifying Double-Sided Materials

To manually add double-sided materials to your model, add <newparam><semantic>DOUBLE_SIDED</semantic></newparam> to the <effect> element. It should resemble the following:

 <effect id="_1_-_Default">
    <profile_COMMON>
       <newparam>
          <semantic>DOUBLE_SIDED</semantic>
       </newparam>        <technique>
           :
           :
       </technique>
    </profile_COMMON>
 </effect>


Tip: You can also clone and flip the faces of your models inside your modeling application to create the back face.

Specifying Opacity map

To force a material to use the Opacity map, locate the <effect> element for the material in the COLLADA file. Under the <effect> element, locate the <transparent> element, which should contain a <color> element. It should resemble the following,

<effect id="material_1-effect">
  <profile_COMMON>
     <technique sid="COMMON">
        <lambert>
           <ambient>
              <color>0.0 0.0 0.0 1.0</color>
           </ambient>
           <diffuse> 
              <texture texture="material_1-sampler" texcoord="UVSET0" />
           </diffuse>
           <transparent>
               <color>1.0 1.0 1.0 1.0</color>           </transparent>
           <transparency>
              <float>1.0</float>
           </transparency>
        </lambert>
     </technique>
  </profile_COMMON>
</effect>

Replace the <color> element under <transparent> with a duplicate of the <texture> element under <diffuse>.

           <transparent>
                 <texture texture="material_1-sampler" texcoord="UVSET0" />           </transparent>
Note: Building Composer has a limitation that it can only use the diffuse map's alpha channel as the opacity map, so both diffuse and opacity map has to be the same map.

Inverting Transparency

Some exporters use a different default transparency definition from Building Composer. You can fix this problem is by changing the transparent mode for the COLLADA materials. Search for and replace all instances of: <transparent> with: <transparent opaque="RGB_ZERO">

Alternatively, search for the following:

<transparency>
  <float>0.00000</float>
</transparency>

and replace it with

<transparency>
  <float>1.00000</float>
</transparency>

You can find out more about transparency in COLLADA in the discussion on collada.org.


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This page has been accessed 4,969 times. This page was last modified on 29 April 2010, at 10:38.


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