5.0 Model Settings

Select the Project->Settings menu option, and select the Model tab. The following property sheet is shown.

The model's Name is the file in which the .m3d file will be stored.  This is the 3D model format used by Real2Virtual Modeller and Viewer.

The rest of the settings control how the model will look, and are called Appearance Settings By default all model groups will use these settings, though any group may override these with it's own particular settings.  See the explanation of these parameters in the section on groups appearance settings. The Texture group selects how the surface (or skin) of the model will look.

• If No Texture is selected then the model will have blank surfaces, with the colour defined in the Surface Colour group.
• If Texture Map is selected then texture from project images (which are texture sources) will be mapped onto the model surface.  In areas of the model not seen in any of the project images the surface will have the colour defined in the Surface Colour group.
• Uniform Texture is selected then texture from the Texture Source Image is applied uniformly over the whole of the model.  Specify a texture scale in each image direction Scale X, and Scale Y.  If the scale is 1 then the texture in the image covers the object once.  For a value of N, it covers the object  when tiled N times.  For N<1 only a fraction of the image is used.

The Smoothing group allow smoothing to be applied to the model. Smoothing rounds off sharp corners. To do this the builder will convert the surface into a Mesh of small triangles which will peice togother to form smooth curves. To enable smoothing select the Do Smoothing checkbox. Then choose the level of detail in the mesh by setting the Mesh Triangles value. This is the number of triangles that will be used to span a distance as large as the model's largest side. A large value corresponds to a high level of detail. The second parameter is Smoothness this dictates how much smoothing will be applied to the mesh. Small values of smoothing will change sharp corners into tightly curved edges, whereas larger value will created more gradual curves.

The Texture Settings gives additional options for use when Texture Mapping

• Colour Resolution of the model defines if it uses colour, and if so how many bits of colour are used.
• Texture Cut Off Angle. If you are mapping texture onto an object from an image, then the texture moves from the image to the surface of the object and 'sticks' only in places where the surfaces are facing that image. So for instance the texture from the front does not end up on the back of the model, as the back surfaces face away from the image. The side faces of the model, however may point slightly forward and texture will be mapped from the front image to these areas, at an angle of approx 90 degrees, the resulting surface texture will not look right, and it would be better to leave these as 'unseen'. To do this specify a non-zero angle for Texture Cut Off. For instance setting this to 5 degrees means that texture from the front will only 'stick' to the surfaces facing toward the front by more than 5 degrees.
• Texture map groups independently. This parameter allows texture mapping to be done on each group as if no-other group existed. This means that objects defined in different groups will not shield each other from recieving texture as happens in normal texture mapping.
• Blend. When texture from two different images join on the surface of the model, a line is often visible where the texture changes from one image source to the other. Select this option to blend smoothly across these join line. Blending will effect all texture within the Blend Range of such joins.

The Shading groups specifies how the model surfaces should be shaded in places which have a Crease. A crease is just a change of direction of the surface, for example a cube has creases on every edge with a crease angle of 90 degrees. Viewers will show creases by shading the area on one side differently to the area on the other, this is caused by the lighting of the model creating shadows. This shading adds realism and makes the object look three-dimensional. Two modes of shading may be used

• Smooth Shading Select the Smooth Shading checkbox for this option. Shading will be done so that crease that have a change of direction smaller than Crease Angle will not be visible, the shading across these creases will be gradual - no discernable 'edge' will be visible. For sharper creases than this angle there will be a sharp change in shading across the crease.
• Flat Shading. Deselect the Smooth Shading checkbox for this option. Flat shading ALWAYS shows creases by sharp shading differences across the crease. All the creases will be visible.

5.1 Refining Texture Mapping

Please note that this section is optional.  Satisfactory models may be generated without requiring any refinement of texture mapping.

Select the Texture Map Details button in the Image Properties dialog, the following dialog is shown, the parameters defined in this dialog are explained below.

Texture Priorities

This process may be modified to be biased in favour a particular image or images by setting what are called Texture Priorities.  The texture priority of every image is initially zero, and no bias is present.  To bias the texture mapping in favour of an image raise it's texture priority.  This can be done from the image properties dialog, enter any positive real number.

Texture Priorities may be used without fully understanding the technicalities of the process, but for those requiring an exact definition read the technical note Understanding Texture Priorities.

For those that only require a rough understanding here are some guidelines,

• If two images have the same priority then conflicts are resolved based purely on viewing positions of the images and the orientation of the model surface.  This is the default mode.
• If the texture priority of image1 is higher that that of image2 then texture mapping prefers the texture from image1.
• If the priority for image1 is higher by a number greater than 1.0, then image1's texture will always win over that of image2 wherever they are in conflict.
• If the priority for image1 is greater by an amount less than 1.0 then conflicts will be resolved based on viewing orientation, but will be biased in favour of image1.  The bias will be greater for higher priority.

Brightness Scale and Shift parameters

The position, size and brightness of the image during texture mapping may be adjusted using these parameters.

To change the brightness of the image enter a multiplying factor in the Brightness edit.  For example to make an image twice as bright the value should be set to 2, and to make it half as bright set the value to 0.5.  The default value is 1, which does not effect the brightness.

To alter the size of the image region mapped to the model enter a scale factor in the Scale edit.  For example to make the texture appear on the model twice as large enter a value of 2.0.  Note that when the texture is made larger, a smaller area of the image is used.

Changes to the positioning of the texture on the model surface can be made by entering non-zero values for XShift and YShift.  These are both in units of Pixels.  To move the texture to the right as you look at the model, specify a positive value of XShift, to move the texture down as you look at the model, specify a positive value of YShift.

Re-defining the camera's focal length

The amount of perspective used whilst texture mapping is by default defined by the choice of project camera.   By changing the focal length of the logical camera used during texture mapping, the amount of perspective  can be changed.  To do this override the camera's focal length by selecting the Re-define Focal Length checkbox.  Enter a new value in pixels in the F edit box.  Note, this will only be used for texture mapping  this image, and does not effect the project's camera definition in general.

Real2Virtual Modeller Documentation Version 0.3
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