Update MaterialX.Supplement.md

add "blend" param to triplanars, formatting fix

Author: dbsmythe

documents/Specification/inprog_v1.39/MaterialX.Supplement.md

@@ -84,6 +84,7 @@ This section describes a number of supplemental nodes for MaterialX.  These node
     * `default` (float or color<em>N</em> or vector<em>N</em>): a default value to use if any `file<em>X</em>` reference can not be resolved (e.g. if a &lt;geomtoken>, [interfacetoken] or {hostattr} is included in the filename but no substitution value or default is defined, or if the resolved file URI cannot be read)  The `default` value must be the same type as the `<triplanarprojection>` element itself.  If `default` is not defined, the default color value will be 0.0 in all channels.
     * `position` (vector3): a spatially-varying input specifying the 3D position at which the projection is evaluated.  Default is to use the current 3D object-space coordinate.
     * `normal` (vector3): a spatially-varying input specifying the 3D normal vector used for blending.  Default is to use the current object-space surface normal.
+    * `blend` (float): a 0-1 weighting factor for blending the three axis samples using the geometric normal, with higher values giving softer blending.  Default is 1.0.
     * `filtertype` (uniform string): the type of texture filtering to use; standard values include "closest" (nearest-neighbor single-sample), "linear", and "cubic".  If not specified, an application may use its own default texture filtering method.
 
     ```
@@ -160,12 +161,13 @@ This section describes a number of supplemental nodes for MaterialX.  These node
 <a id="node-triplanarblend"> </a>
 
 * **`triplanarblend`**: samples data from three inputs, and projects a tiled representation of the images along each of the three respective coordinate axes, computing a weighted blend of the three samples using the geometric normal.
-    * inx (float or colorN): the image to be projected in the direction from the +X axis back toward the origin.  Default is 0 in all channels.
-    * iny (float or colorN): the image to be projected in the direction from the +Y axis back toward the origin with the +X axis to the right.  Default is 0 in all channels.
-    * inz (float or colorN): the image to be projected in the direction from the +Z axis back toward the origin.  Default is 0 in all channels.
-    * position (vector3): a spatially-varying input specifying the 3D position at which the projection is evaluated.  Default is to use the current 3D object-space coordinate.
-    * normal (vector3): a spatially-varying input specifying the 3D normal vector used for blending.  Default is to use the current object-space surface normal.
-    * filtertype (uniform string): the type of texture filtering to use; standard values include "closest" (nearest-neighbor single-sample), "linear", and "cubic".  If not specified, an application may use its own default texture filtering method.
+    * `inx` (float or colorN): the image to be projected in the direction from the +X axis back toward the origin.  Default is 0 in all channels.
+    * `iny` (float or colorN): the image to be projected in the direction from the +Y axis back toward the origin with the +X axis to the right.  Default is 0 in all channels.
+    * `inz` (float or colorN): the image to be projected in the direction from the +Z axis back toward the origin.  Default is 0 in all channels.
+    * `position` (vector3): a spatially-varying input specifying the 3D position at which the projection is evaluated.  Default is to use the current 3D object-space coordinate.
+    * `normal` (vector3): a spatially-varying input specifying the 3D normal vector used for blending.  Default is to use the current object-space surface normal.
+    * `blend` (float): a 0-1 weighting factor for blending the three axis samples using the geometric normal, with higher values giving softer blending.  Default is 1.0.
+    * `filtertype` (uniform string): the type of texture filtering to use; standard values include "closest" (nearest-neighbor single-sample), "linear", and "cubic".  If not specified, an application may use its own default texture filtering method.