Finish triangle code and add triangle example to app

Raster3D.App/Game.cs

@@ -18,8 +18,18 @@ namespace Raster3D.App
 
         public override void exec(Engine.Engine engine)
         {
-            Line line = new Line(new Vec2D(0, 30), new Vec2D(30,60), engine);
-            line._Draw();
+            Vec2D[] points = new Vec2D[3];
+            points[0] = new Vec2D(32, 32);
+            points[1] = new Vec2D(64, 32);
+            points[2] = new Vec2D(64, 64);
+
+            rgb[] colors = new rgb[3];
+            colors[0] = new rgb(1.0f, 0.0f, 0.0f); // red
+            colors[1] = new rgb(0.0f, 1.0f, 0.0f); // green
+            colors[2] = new rgb(0.0f, 0.0f, 1.0f); // blue
+
+            Triangle triangle = new Triangle(points, colors, engine);
+            triangle._Draw();
         }
     }
 }

Raster3D/Objects/Triangle.cs

@@ -26,9 +26,13 @@ namespace Raster3D.Engine.Objects
 
         public void _Draw()
         {
-            children.Append(new Line(_positions[0], _positions[1], _clrs[0], _engine));
-            children.Append(new Line(_positions[1], _positions[2], _clrs[1], _engine));
-            children.Append(new Line(_positions[2], _positions[1], _clrs[2], _engine));
+            children[0] = (new Line(_positions[0], _positions[1], _clrs[0], _engine));
+            children[1] = (new Line(_positions[1], _positions[2], _clrs[1], _engine));
+            children[2] = (new Line(_positions[2], _positions[0], _clrs[2], _engine));
+            foreach (var child in children)
+            {
+                child._Draw();
+            }
         }
 
         public void _Free()