Add triangle wave node (#1334)

This node generates values from zero to one based on the input value.

Author: Cinifreak

libraries/stdlib/stdlib_defs.mtlx

@@ -2546,6 +2546,16 @@
     <output name="out" type="stringarray" defaultinput="in1" />
   </nodedef>
 
+  <!--
+    Node: <trianglewave>
+    Generate a triangle wave from the given scalar input.
+    The generated wave ranges from zero to one and repeats on integer boundaries.
+  -->
+  <nodedef name="ND_trianglewave_float" node="trianglewave" nodegroup="math">
+    <input name="in" type="float" value="0" />
+    <output name="out" type="float" />
+  </nodedef>
+
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libraries/stdlib/stdlib_ng.mtlx

@@ -1540,6 +1540,32 @@
     </magnitude>
     <output name="out" type="float" nodename="N_mtlxmagnitude" />
   </nodegraph>
+  
+  <!--
+    Node: <trianglewave>
+    Generate a triangle wave from the given scalar input.
+    The generated wave ranges from zero to one and repeats on integer boundaries.
+  -->
+  <nodegraph name="NG_trianglewave_float" nodedef="ND_trianglewave_float">
+    <absval name="absval1" type="float">
+      <input name="in" type="float" interfacename="in" />
+    </absval>
+    <modulo name="modulo1" type="float">
+      <input name="in1" type="float" nodename="absval1" />
+    </modulo>
+    <subtract name="subtract1" type="float">
+      <input name="in1" type="float" nodename="modulo1" />
+      <input name="in2" type="float" value="0.5" />
+    </subtract>
+    <absval name="absval2" type="float">
+      <input name="in" type="float" nodename="subtract1" />
+    </absval>
+    <subtract name="subtract2" type="float">
+      <input name="in1" type="float" value="0.5" />
+      <input name="in2" type="float" nodename="absval2" />
+    </subtract>
+    <output name="out" type="float" nodename="subtract2" />
+  </nodegraph>
 
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   <!-- Adjustment nodes                                                         -->