Show Edges and Wireframe

This example includes two related examples:

• ShowEdges is a basic mental ray shader that draws a thick border along the edges of a polygon mesh. ShowEdges renders the triangulated version of the mesh that is sent to mental ray.

• Wireframe also draws edges, but it shows the true edges (before tesselation). Wireframe uses a UserDataBlob to pass edge information to a shader (which shows how to map Softimage user data into mental ray user data). A custom operator populates the UserDataBlob with the edge information. An operator is used rather than a custom command because whenever the geometry changes, Softimage re-evaluates the operator and re-renders the object. The operater and the shader are contained in the same DLL/SO, and this file is located in the Application\Plugins directory instead of the conventional shader directory (Application\bin\{CPU}) so that Softimage automatically loads it as a self-installed plugin. This approach is convenient for implementing both a shader and an operator together in an single dll, but it means that the normal ability to have multiple platform binaries on a single workgroup would not work. To support that configuration the example would be implemented as two separate dlls.

The difference between Wireframe and ShowEdges is illustrated in the figure below, which shows how the two examples render the same mesh.

Comparison of Wireframe and ShowEdges

Example Files

Location
ShowEdges	show_edges.spdl show_edges.cpp show_edges.h show_edges_dll.cpp show_edges.vcproj GNUmakefile
WireFrame Files	WireframeOp.cpp WireframeShader.cpp WireframeShader.spdl Wireframe.vcproj GNUmakefile

Running the Example

To run the ShowEdges example

1. In a script editor, run this demo script:

   // [ Jscript ] Demo script for ShowEdges
   
   NewScene( null, false );
   var oSphere = ActiveSceneRoot.AddGeometry( "Sphere", "MeshSurface" );
   SelectObj( oSphere );
   
   var oMaterial = oSphere.AddMaterial( "show_edges.Preset",false,"ShowEdges");
   InspectObj( oMaterial.Parameters("Surface").Source );
   

2. Draw a render region.

To run the Wireframe example

1. In a script editor, run this demo script:

   '[VBScript] Demo program for the Wireframe Softimage shader example
   
   NewScene , false
   
   ' Create test sphere
   set object = ActiveSceneRoot.AddGeometry( "Sphere", "MeshSurface" )
   
   SetupObject object
   
   'Shadow effect
   set oGrid = ActiveSceneRoot.AddGeometry( "Grid", "MeshSurface" )
   Translate oGrid, 0, -5, 0, siAbsolute, siParent, siObj, siY
   oGrid.ulength = 100
   oGrid.vlength = 100
   SetValue "light.light.soft_light.shadow", True
   
   sub SetupObject( in_obj )
   
   	' Add the UserDataBlob property and set it renderable
   	' The UserDataID must be set to the specific ID that
   	' the shader is expecting
   
   	set prop = in_obj.AddProperty( "UserDataBlob" )
   	prop.RenderData = True
   	prop.UserDataID = 6789
   
   	on error resume next
   	prop.AddCustomOp "WireframeOp",in_obj.ActivePrimitive
   
   	if ( err <> 0 ) then
   		MsgBox "Failed to create WriteframeOp Custom Operator" & vbCrLf & _
   				"Please make sure the example is fully installed"
   		exit sub
   	end if
   
   	on error goto 0
   
   	' Add wireframe shader to an empty material
   	set material = in_obj.AddMaterial
   	set oSurfParam = material.Parameters( "surface" )
   
   	set oSpriteShader = oSurfParam.connectfrompreset( "Sprite", siMaterialShaderFamily )
   
   	material.Parameters("Shadow").Connect( oSpriteShader )
   
   
   	set inputParam = oSpriteShader.Parameters( "input" )
   
   	on error resume next
   	set oWireShader = inputParam.connectfrompreset( "WireframeShader", siTextureShaderFamily )
   
   	if ( err <> 0 ) then
   		MsgBox "Failed to create WriteframeShader " & vbCrLf & _
   				"Please make sure the example is fully installed"
   		exit sub
   	end if
   
   	oWireShader.Parameters("wire_width").value = 0.1
   	oWireShader.Parameters("base_color").Parameters("red").value = 1
   	oWireShader.Parameters("base_color").Parameters("green").value = 1
   	oWireShader.Parameters("base_color").Parameters("blue").value = 1
   	oWireShader.Parameters("base_color").Parameters("alpha").value = 0
   
   	InspectObj oWireShader
   end sub
   

2. Draw a render region.

Building the C++ Example

The Softimage SDK includes a compiled version of ShowEdges. If you want to modify the code, you can rebuild the shader by following these instructions.