Editing Appendix/Ramblings/VirtualReality (section)

====Implementing the Raw COLLADA Code====

We have found another relatively simple COLLADA-formatted 3D model file on a [https://developer.blender.org/F18376 web page titled, "cube.dae,"] that has been provided by [https://www.blender.org Blender] author, Martjn Berger.  The interactive scene that is generated by this model file includes three separate &#8212; but identical &#8212; cubes; four of the cube faces are painted with one color (e.g., blue), another face is painted with a different color (e.g., green), and the sixth face is painted with yet a different color (e.g., red).  The COLLADA-formatted (.dae) file presented immediately below as ''Example #4'' is modified slightly from this original [https://www.blender.org Blender] example; on my Mac, the filename is: '''/Dropbox/3Dviewers/Cube/FirstCube/colladaPlay06.dae'''


<table border="0" align="center" width="80%" cellpadding="5">
<tr><th align="center" colspan="3">Example #4 &#8212; A [https://developer.blender.org/F18376 cube trio], slightly modified from a COLLADA file posted by [https://www.blender.org Blender]</th></tr>
<tr><td align="left" colspan="2">
<div style="height: 400px; width: 700px; overflow: scroll;">
<pre>
<?xml version="1.0" encoding="UTF-8" standalone="no" ?>
<COLLADA xmlns="http://www.collada.org/2005/11/COLLADASchema" version="1.4.1">
    <asset>
        <contributor>
            <authoring_tool>Google SketchUp 8.0.11752</authoring_tool>
        </contributor>
        <created>2012-04-27T21:07:03Z</created>
        <modified>2012-04-27T21:07:03Z</modified>
        <unit meter="0.0254" name="inch" />
        <up_axis>Z_UP</up_axis>
    </asset>
    <library_visual_scenes>
        <visual_scene id="ID1">
            <node name="SketchUp">
                <node id="ID2" name="instance_0">
                    <matrix>1 0 0 0 0 1 0 25 0 0 1 0 0 0 0 1</matrix>
                    <instance_node url="#ID3" />
                </node>
                <node id="ID28" name="instance_1">
                    <matrix>1 0 0 15 0 1 0 120 0 0 1 0 0 0 0 1</matrix>
                    <instance_node url="#ID3" />
                </node>
                <node id="ID29" name="instance_2">
                    <matrix>1 0 0 120 0 1 0 0 0 0 1 0 0 0 0 1</matrix>
                    <instance_node url="#ID3" />
                </node>
            </node>
        </visual_scene>
    </library_visual_scenes>
    <library_nodes>
        <node id="ID3" name="cube_component">
            <instance_geometry url="#ID4">
                <bind_material>
                    <technique_common>
                        <instance_material symbol="Material2" target="#ID6">
                            <bind_vertex_input semantic="UVSET0" input_semantic="TEXCOORD" input_set="0" />
                        </instance_material>
                    </technique_common>
                </bind_material>
            </instance_geometry>
            <instance_geometry url="#ID12">
                <bind_material>
                    <technique_common>
                        <instance_material symbol="Material2" target="#ID13">
                            <bind_vertex_input semantic="UVSET0" input_semantic="TEXCOORD" input_set="0" />
                        </instance_material>
                    </technique_common>
                </bind_material>
            </instance_geometry>
            <instance_geometry url="#ID20">
                <bind_material>
                    <technique_common>
                        <instance_material symbol="Material2" target="#ID21">
                            <bind_vertex_input semantic="UVSET0" input_semantic="TEXCOORD" input_set="0" />
                        </instance_material>
                    </technique_common>
                </bind_material>
            </instance_geometry>
        </node>
    </library_nodes>
    <library_geometries>
        <geometry id="ID4">
            <mesh>
                <source id="ID7">
                    <float_array id="ID10" count="48">39.37007874015748 39.37007874015748 0 0 0 0 0 39.37007874015748 0 39.37007874015748 0 0 0 39.37007874015748 39.37007874015748 39.37007874015748 39.37007874015748 0 0 39.37007874015748 0 39.37007874015748 39.37007874015748 39.37007874015748 39.37007874015748 39.37007874015748 0 39.37007874015748 0 39.37007874015748 39.37007874015748 0 0 39.37007874015748 39.37007874015748 39.37007874015748 39.37007874015748 0 39.37007874015748 0 39.37007874015748 39.37007874015748 0 0 39.37007874015748 39.37007874015748 39.37007874015748 39.37007874015748</float_array>
                    <technique_common>
                        <accessor count="16" source="#ID10" stride="3">
                            <param name="X" type="float" />
                            <param name="Y" type="float" />
                            <param name="Z" type="float" />
                        </accessor>
                    </technique_common>
                </source>
                <source id="ID8">
                    <float_array id="ID11" count="48">0 0 -1 0 0 -1 0 0 -1 0 0 -1 0 1 0 0 1 0 0 1 0 0 1 0 1 0 0 1 0 0 1 0 0 1 0 0 0 0 1 0 0 1 0 0 1 0 0 1</float_array>
                    <technique_common>
                        <accessor count="16" source="#ID11" stride="3">
                            <param name="X" type="float" />
                            <param name="Y" type="float" />
                            <param name="Z" type="float" />
                        </accessor>
                    </technique_common>
                </source>
                <vertices id="ID9">
                    <input semantic="POSITION" source="#ID7" />
                    <input semantic="NORMAL" source="#ID8" />
                </vertices>
                <triangles count="8" material="Material2">
                    <input offset="0" semantic="VERTEX" source="#ID9" />
                    <p>0 1 2 1 0 3 4 5 6 5 4 7 8 9 10 9 8 11 12 13 14 13 12 15</p>
                </triangles>
            </mesh>
        </geometry>
        <geometry id="ID12">
            <mesh>
                <source id="ID15">
                    <float_array id="ID18" count="12">39.37007874015748 0 39.37007874015748 0 0 0 39.37007874015748 0 0 0 0 39.37007874015748</float_array>
                    <technique_common>
                        <accessor count="4" source="#ID18" stride="3">
                            <param name="X" type="float" />
                            <param name="Y" type="float" />
                            <param name="Z" type="float" />
                        </accessor>
                    </technique_common>
                </source>
                <source id="ID16">
                    <float_array id="ID19" count="12">-0 -1 -0 -0 -1 -0 -0 -1 -0 -0 -1 -0</float_array>
                    <technique_common>
                        <accessor count="4" source="#ID19" stride="3">
                            <param name="X" type="float" />
                            <param name="Y" type="float" />
                            <param name="Z" type="float" />
                        </accessor>
                    </technique_common>
                </source>
                <vertices id="ID17">
                    <input semantic="POSITION" source="#ID15" />
                    <input semantic="NORMAL" source="#ID16" />
                </vertices>
                <triangles count="2" material="Material2">
                    <input offset="0" semantic="VERTEX" source="#ID17" />
                    <p>0 1 2 1 0 3</p>
                </triangles>
            </mesh>
        </geometry>
        <geometry id="ID20">
            <mesh>
                <source id="ID23">
                    <float_array id="ID26" count="12">0 39.37007874015748 39.37007874015748 0 0 0 0 0 39.37007874015748 0 39.37007874015748 0</float_array>
                    <technique_common>
                        <accessor count="4" source="#ID26" stride="3">
                            <param name="X" type="float" />
                            <param name="Y" type="float" />
                            <param name="Z" type="float" />
                        </accessor>
                    </technique_common>
                </source>
                <source id="ID24">
                    <float_array id="ID27" count="12">-1 0 0 -1 0 0 -1 0 0 -1 0 0</float_array>
                    <technique_common>
                        <accessor count="4" source="#ID27" stride="3">
                            <param name="X" type="float" />
                            <param name="Y" type="float" />
                            <param name="Z" type="float" />
                        </accessor>
                    </technique_common>
                </source>
                <vertices id="ID25">
                    <input semantic="POSITION" source="#ID23" />
                    <input semantic="NORMAL" source="#ID24" />
                </vertices>
                <triangles count="2" material="Material2">
                    <input offset="0" semantic="VERTEX" source="#ID25" />
                    <p>0 1 2 1 0 3</p>
                </triangles>
            </mesh>
        </geometry>
    </library_geometries>
    <library_materials>
        <material id="ID6" name="material">
            <instance_effect url="#ID5" />
        </material>
        <material id="ID13" name="Color_005_">
            <instance_effect url="#ID14" />
        </material>
        <material id="ID21" name="Color_A06_">
            <instance_effect url="#ID22" />
        </material>
    </library_materials>
    <library_effects>
        <effect id="ID5">
            <profile_COMMON>
                <technique sid="COMMON">
                    <lambert>
                        <diffuse>
                            <color>0 0 1 1</color>
                        </diffuse>
                    </lambert>
                </technique>
            </profile_COMMON>
        </effect>
        <effect id="ID14">
            <profile_COMMON>
                <technique sid="COMMON">
                    <lambert>
                        <diffuse>
                            <color>0 1 0 1</color>
                        </diffuse>
                    </lambert>
                </technique>
            </profile_COMMON>
        </effect>
        <effect id="ID22">
            <profile_COMMON>
                <technique sid="COMMON">
                    <lambert>
                        <diffuse>
                            <color>0.8 0 0 1</color>
                        </diffuse>
                    </lambert>
                </technique>
            </profile_COMMON>
        </effect>
    </library_effects>
    <scene>
        <instance_visual_scene url="#ID1" />
    </scene>
</COLLADA>
</pre>
</div>
</td>
<td align="center" rowspan="1" bgcolor="lightgrey">[[File:ColladaPlay06_image.png|250px|ColladaPlay06_image]]</td>
</tr>
<tr>
  <td align="left" colspan="3">
<b>Principal responsibilities of various subsections from the above, <xml>-formatted code:</b>
  </td>
</tr>
<tr>
  <td align="center" width="50px" bgcolor="yellow">'''A.'''</td>
  <td align="left" colspan="2">
<pre>
<library_visual_scenes>
  <visual_scene ID="ID1">
    <node name="SketcUp">
</pre>
<font color="darkblue">Generate 3 ''instances'' of </font><font color="green">#ID3</font><font color="darkblue">, placing them at 3 separate 16-argument "matrix" positions, as [[#Understanding_the_Positioning_Matrix|explained below]].</font>
<pre>
    </node>
  </visual_scene>
</library_visual_scenes>
</pre>
  </td>
</tr>

<tr>
  <td align="center" width="50px" bgcolor="lightblue">'''B.'''</td>
  <td align="left" colspan="2">
<pre>
<library_nodes>
  <node id="ID3">
</pre>
<font color="darkblue">Define all components of a ''single node'' that describes a simple, 6-sided (8 vertices and 12 triangles) cube; this implementation builds the cube as being composed of ''three'' separate <instance_geometries>, as defined below:</font>
<ul>
  <li><font color="#FF9999"><b>url = "</b></font><font color="darkgreen">#ID4</font><font color="#FF9999"><b>" should be colored/shaded as defined by material target = "</b></font><font color="darkgreen">#ID6</font><font color="#FF9999"><b>", which in turn points to library effect = "</b></font><font color="darkgreen">#ID5</font><font color="#FF9999"><b>".</b></font></li>
  <li><font color="#FF9999"><b>url = "</b></font><font color="darkgreen">#ID12</font><font color="#FF9999"><b>" should be colored/shaded as defined by material target = "</b></font><font color="darkgreen">#ID13</font><font color="#FF9999"><b>", which in turn points to library effect = "</b></font><font color="darkgreen">#ID14</font><font color="#FF9999"><b>".</b></font></li>
  <li><font color="#FF9999"><b>url = "</b></font><font color="darkgreen">#ID20</font><font color="#FF9999"><b>" should be colored/shaded as defined by material target = "</b></font><font color="darkgreen">#ID21</font><font color="#FF9999"><b>", which in turn points to library effect = "</b></font><font color="darkgreen">#ID22</font><font color="#FF9999"><b>".</b></font></li>
</ul>
<pre>
  </node>
</library_nodes>
</pre>
  </td>
</tr>

<tr>
  <td align="center" width="50px" bgcolor="yellow">'''C.'''</td>
  <td align="left" colspan="2">
<pre>
<library_geometries>
  <geometry id="&hellip;">
</pre>
<font color="darkblue">Two co-planar and adjacent triangles are prescribed such that, together, they define a square, which serves as ''one'' of the six sides of the cube; ''four'' unique vertices are required, referenced as &hellip; 0, 1, 2, 3.</font><br />
<mesh><br />
&nbsp; &nbsp; <vertices id="<font color="darkgreen">ID17</font>">
<ul>
  <li><font color="#FF9999"><b>(X, Y, Z) coordinate locations are pulled from</b></font> <source id="<font color="darkgreen">ID15</font>"> <font color="#FF9999"><b>, which contains a total of 4 &times; 3 = 12 floating-point numbers.</b></font></li>
  <li><font color="#FF9999"><b>The (X, Y, Z)-normals assigned to the four vertices are pulled from</b></font> <source id="<font color="darkgreen">ID16</font>"> <font color="#FF9999"><b>, which also contains a total of 4 &times; 3 = 12 floating-point numbers &hellip; the assigned values are usually 0 or &plusmn; 1.</b></font></li>
</ul>
&nbsp; &nbsp; </vertices><br />
&nbsp; &nbsp; <triangles source="<font color="darkgreen">#ID17</font>" count="2"><br />
&nbsp; &nbsp; &lt;p&gt;0 1 2    1 0 3&lt;/p&gt;
<ul>
  <li><font color="#FF9999"><b>This sequence of six integers means that the 1<sup>st</sup> (of count="2") triangular polygon is formed by connecting three vertices in the order &hellip; 0, 1, 2, then back to 0; and the 2<sup>nd</sup> (of count="2") triangular polygon is formed by connecting three vertices in the order &hellip; 1, 0, 3, then back to 1.</b></font></li>
</ul>
&nbsp; &nbsp; </triangles><br />
</mesh>
<pre>
  </geometry>
</library_geometries>
</pre>
  </td>
</tr>
</table>