source/blender/nodes/shader/CMakeLists.txt

@@ -165,6 +165,7 @@ if(WITH_MATERIALX)
     materialx/material.h
     materialx/nodes/node_item.h
     materialx/nodes/node_parser.h
+    materialx/nodes/output_material.h
   )
   list(APPEND LIB
     MaterialXCore

source/blender/nodes/shader/materialx/material.cc

@@ -3,7 +3,7 @@
  * SPDX-License-Identifier: GPL-2.0-or-later */
 
 #include "material.h"
-#include "nodes/node_parser.h"
+#include "nodes/output_material.h"
 
 #include <MaterialXFormat/XmlIo.h>
 
@@ -17,43 +17,27 @@ namespace blender::nodes::materialx {
 
 CLG_LOGREF_DECLARE_GLOBAL(LOG_MATERIALX_SHADER, "materialx.shader");
 
-static void export_nodegraph(MaterialX::GraphElement *graph,
+MaterialX::DocumentPtr export_to_materialx(Depsgraph *depsgraph,
-                             Depsgraph *depsgraph,
+                                           Material *material,
-                             Material *material)
+                                           const std::string &socket_name)
 {
-  material->nodetree->ensure_topology_cache();
+  CLOG_INFO(LOG_MATERIALX_SHADER, 0, "Material: %s", material->id.name);
 
-  bNode *output_node = ntreeShaderOutputNode(material->nodetree, SHD_OUTPUT_ALL);
-  OutputMaterialNodeParser parser(graph, depsgraph, material, output_node);
-  parser.compute();
-}
-
-static void create_standard_surface(MaterialX::GraphElement *graph, Material *material)
-{
-  MaterialX::NodePtr standard_surface = graph->addNode(
-      "standard_surface", MaterialX::EMPTY_STRING, "surfaceshader");
-
-  standard_surface->addInput("base", "float")->setValue(1.0);
-  standard_surface->addInput("base_color", "color3")
-      ->setValue(MaterialX::Color3(material->r, material->g, material->b));
-
-  MaterialX::NodePtr surfacematerial = graph->addNode(
-      "surfacematerial", MaterialX::EMPTY_STRING, "material");
-  surfacematerial->addInput(standard_surface->getType(), standard_surface->getType())
-      ->setNodeName(standard_surface->getName());
-}
-
-MaterialX::DocumentPtr export_to_materialx(Depsgraph *depsgraph, Material *material)
-{
   MaterialX::DocumentPtr doc = MaterialX::createDocument();
   if (material->use_nodes) {
-    export_nodegraph(doc.get(), depsgraph, material);
+    material->nodetree->ensure_topology_cache();
+    bNode *output_node = ntreeShaderOutputNode(material->nodetree, SHD_OUTPUT_ALL);
+    OutputMaterialNodeParser(doc.get(), depsgraph, material, output_node).compute(socket_name);
   }
   else {
-    create_standard_surface(doc.get(), material);
+    OutputMaterialNodeParser(doc.get(), depsgraph, material, nullptr).compute_default();
   }
-  std::string str = MaterialX::writeToXmlString(doc);
+
-  CLOG_INFO(LOG_MATERIALX_SHADER, 1, "Material: %s\n%s", material->id.name, str.c_str());
+  CLOG_INFO(LOG_MATERIALX_SHADER,
+            2,
+            "Material: %s\n%s",
+            material->id.name,
+            MaterialX::writeToXmlString(doc).c_str());
   return doc;
 }
 

source/blender/nodes/shader/materialx/material.h

@@ -15,6 +15,8 @@ namespace blender::nodes::materialx {
 
 extern struct CLG_LogRef *LOG_MATERIALX_SHADER;
 
-MaterialX::DocumentPtr export_to_materialx(Depsgraph *depsgraph, Material *material);
+MaterialX::DocumentPtr export_to_materialx(Depsgraph *depsgraph,
+                                           Material *material,
+                                           const std::string &socket_name = "Surface");
 
 }  // namespace blender::nodes::materialx

source/blender/nodes/shader/materialx/nodes/bsdf_principled.cc

@@ -68,7 +68,7 @@ NodeItem BSDFPrincipledNodeParser::compute()
   NodeItem tangent = get_input_link("Tangent");
 
   /* Creating standard_surface */
-  NodeItem res = create_node("standard_surface", "surfaceshader", false);
+  NodeItem res = create_node("standard_surface", "surfaceshader");
   res.set_input("base", 1.0, "float");
   res.set_input("base_color", base_color.to_color3());
   res.set_input("diffuse_roughness", roughness);
@@ -90,9 +90,11 @@ NodeItem BSDFPrincipledNodeParser::compute()
     res.set_input("specular_IOR", ior);
     if (anisotropic) {
       res.set_input("specular_anisotropy", anisotropic);
+      if (anisotropic_rotation) {
         res.set_input("specular_rotation", anisotropic_rotation);
       }
     }
+  }
 
   if (transmission != zero) {
     res.set_input("transmission", transmission);

source/blender/nodes/shader/materialx/nodes/hueSatVal.cc

@@ -23,7 +23,7 @@ NodeItem HueSatValNodeParser::compute()
   combine.set_input("in2", saturation);
   combine.set_input("in3", val);
 
-  NodeItem res = create_node("hsvadjust", "color3", false);
+  NodeItem res = create_node("hsvadjust", "color3");
   res.set_input("in", color.to_color3());
   res.set_input("amount", combine);
   return res;

source/blender/nodes/shader/materialx/nodes/math.cc

@@ -10,7 +10,7 @@ namespace blender::nodes::materialx {
 NodeItem MathNodeParser::compute()
 {
   /* TODO: finish some math operations */
-  auto op = node->custom1;
+  auto op = node_->custom1;
   NodeItem res = empty();
 
   /* Single operand operations */
@@ -158,7 +158,7 @@ NodeItem MathNodeParser::compute()
     }
   }
 
-  bool clamp_output = node->custom2 != 0;
+  bool clamp_output = node_->custom2 != 0;
   if (clamp_output && res) {
     res = res.clamp();
   }

source/blender/nodes/shader/materialx/nodes/node_parser.cc

@@ -12,56 +12,59 @@ namespace blender::nodes::materialx {
 NodeParser::NodeParser(MaterialX::GraphElement *graph,
                        const Depsgraph *depsgraph,
                        const Material *material,
-                       const bNode *node)
+                       const bNode *node,
-    : graph(graph), depsgraph(depsgraph), material(material), node(node)
+                       const bNodeSocket *socket_out)
+    : graph_(graph), depsgraph_(depsgraph), material_(material), node_(node), socket_out_(socket_out)
 {
 }
 
-NodeItem NodeParser::create_node(const std::string &mx_category,
+std::string NodeParser::node_name(const bNode *node, const bNodeSocket *socket_out)
-                                 const std::string &mx_type,
+{
-                                 bool noname)
+  return MaterialX::createValidName(node->output_sockets().size() <= 1 ?
+                                        std::string(node->name) :
+                                        std::string(node->name) + "_" + socket_out->name);
+}
+
+NodeItem NodeParser::create_node(const std::string &mx_category, const std::string &mx_type)
 {
   NodeItem res = empty();
-  res.node = graph->addNode(mx_category,
+  res.node = graph_->addNode(mx_category, MaterialX::EMPTY_STRING, mx_type);
-                            noname ? MaterialX::EMPTY_STRING :
-                                     MaterialX::createValidName(node->name),
-                            mx_type);
   return res;
 }
 
 NodeItem NodeParser::get_input_default(const std::string &name)
 {
-  return get_input_default(node->input_by_identifier(name));
+  return get_input_default(node_->input_by_identifier(name));
 }
 
 NodeItem NodeParser::get_input_default(int index)
 {
-  return get_input_default(node->input_socket(index));
+  return get_input_default(node_->input_socket(index));
 }
 
 NodeItem NodeParser::get_input_link(const std::string &name)
 {
-  return get_input_link(node->input_by_identifier(name));
+  return get_input_link(node_->input_by_identifier(name));
 }
 
 NodeItem NodeParser::get_input_link(int index)
 {
-  return get_input_link(node->input_socket(index));
+  return get_input_link(node_->input_socket(index));
 }
 
 NodeItem NodeParser::get_input_value(const std::string &name)
 {
-  return get_input_value(node->input_by_identifier(name));
+  return get_input_value(node_->input_by_identifier(name));
 }
 
 NodeItem NodeParser::get_input_value(int index)
 {
-  return get_input_value(node->input_socket(index));
+  return get_input_value(node_->input_socket(index));
 }
 
 NodeItem NodeParser::empty() const
 {
-  return NodeItem(graph);
+  return NodeItem(graph_);
 }
 
 NodeItem NodeParser::get_input_default(const bNodeSocket &socket)
@@ -98,59 +101,49 @@ NodeItem NodeParser::get_input_link(const bNodeSocket &socket)
     return res;
   }
 
-  const bNode *in_node = link->fromnode;
+  const bNode *from_node = link->fromnode;
 
   /* Passing NODE_REROUTE nodes */
-  while (in_node->type == NODE_REROUTE) {
+  while (from_node->type == NODE_REROUTE) {
-    link = in_node->input_socket(0).link;
+    link = from_node->input_socket(0).link;
     if (!(link && link->is_used())) {
       return res;
     }
-    in_node = link->fromnode;
+    from_node = link->fromnode;
   }
 
-  /* Getting required NodeParser object */
+  /* Checking if node was already computed */
-  std::unique_ptr<NodeParser> parser;
+  res.node = graph_->getNode(node_name(from_node, link->fromsock));
-  switch (in_node->typeinfo->type) {
+  if (res.node) {
-    case SH_NODE_BSDF_PRINCIPLED:
-      parser = std::make_unique<BSDFPrincipledNodeParser>(graph, depsgraph, material, in_node);
-      break;
-    case SH_NODE_INVERT:
-      parser = std::make_unique<InvertNodeParser>(graph, depsgraph, material, in_node);
-      break;
-    case SH_NODE_HUE_SAT:
-      parser = std::make_unique<HueSatValNodeParser>(graph, depsgraph, material, in_node);
-      break;
-    case SH_NODE_MATH:
-      parser = std::make_unique<MathNodeParser>(graph, depsgraph, material, in_node);
-      break;
-    case SH_NODE_MIX_RGB_LEGACY:
-      parser = std::make_unique<MixRGBNodeParser>(graph, depsgraph, material, in_node);
-      break;
-    case SH_NODE_NORMAL_MAP:
-      parser = std::make_unique<NormalMapNodeParser>(graph, depsgraph, material, in_node);
-      break;
-    case SH_NODE_TEX_IMAGE:
-      parser = std::make_unique<TexImageNodeParser>(graph, depsgraph, material, in_node);
-      break;
-    case SH_NODE_TEX_ENVIRONMENT:
-      parser = std::make_unique<TexEnvironmentNodeParser>(graph, depsgraph, material, in_node);
-      break;
-    case SH_NODE_TEX_NOISE:
-      parser = std::make_unique<TexNoiseNodeParser>(graph, depsgraph, material, in_node);
-      break;
-    case SH_NODE_TEX_CHECKER:
-      parser = std::make_unique<TexCheckerNodeParser>(graph, depsgraph, material, in_node);
-      break;
-    case SH_NODE_VECTOR_MATH:
-      parser = std::make_unique<VectorMathNodeParser>(graph, depsgraph, material, in_node);
-      break;
-    default:
-      CLOG_WARN(LOG_MATERIALX_SHADER, "Unsupported node: %s (%d)", in_node->name, in_node->type);
     return res;
   }
 
-  res = parser->compute();
+  /* Computing from_node with required NodeParser object */
+#define CASE_NODE_TYPE(type, T) \
+  case type: \
+    res = T(graph_, depsgraph_, material_, from_node, link->fromsock).compute_full(); \
+    break;
+
+  switch (from_node->typeinfo->type) {
+    CASE_NODE_TYPE(SH_NODE_BSDF_PRINCIPLED, BSDFPrincipledNodeParser)
+    CASE_NODE_TYPE(SH_NODE_HUE_SAT, HueSatValNodeParser)
+    CASE_NODE_TYPE(SH_NODE_INVERT, InvertNodeParser)
+    CASE_NODE_TYPE(SH_NODE_MATH, MathNodeParser)
+    CASE_NODE_TYPE(SH_NODE_MIX_RGB_LEGACY, MixRGBNodeParser)
+    CASE_NODE_TYPE(SH_NODE_NORMAL_MAP, NormalMapNodeParser)
+    CASE_NODE_TYPE(SH_NODE_TEX_CHECKER, TexCheckerNodeParser)
+    CASE_NODE_TYPE(SH_NODE_TEX_ENVIRONMENT, TexEnvironmentNodeParser)
+    CASE_NODE_TYPE(SH_NODE_TEX_IMAGE, TexImageNodeParser)
+    CASE_NODE_TYPE(SH_NODE_TEX_NOISE, TexNoiseNodeParser)
+    CASE_NODE_TYPE(SH_NODE_VECTOR_MATH, VectorMathNodeParser)
+
+    default:
+      CLOG_WARN(LOG_MATERIALX_SHADER,
+                "Unsupported node: %s [%d]",
+                from_node->name,
+                from_node->typeinfo->type);
+  }
+
   return res;
 }
 
@@ -163,4 +156,14 @@ NodeItem NodeParser::get_input_value(const bNodeSocket &socket)
   return res;
 }
 
+NodeItem NodeParser::compute_full()
+{
+  CLOG_INFO(LOG_MATERIALX_SHADER, 1, "%s [%d]", node_->name, node_->typeinfo->type);
+  NodeItem res = compute();
+  if (res.node) {
+    res.node->setName(node_name(node_, socket_out_));
+  }
+  return res;
+}
+
 }  // namespace blender::nodes::materialx

source/blender/nodes/shader/materialx/nodes/node_parser.h

@@ -13,25 +13,26 @@
 namespace blender::nodes::materialx {
 
 class NodeParser {
- public:
+ protected:
-  MaterialX::GraphElement *graph;
+  MaterialX::GraphElement *graph_;
-  const Depsgraph *depsgraph;
+  const Depsgraph *depsgraph_;
-  const Material *material;
+  const Material *material_;
-  const bNode *node;
+  const bNode *node_;
+  const bNodeSocket *socket_out_;
 
  public:
   NodeParser(MaterialX::GraphElement *graph,
              const Depsgraph *depsgraph,
              const Material *material,
-             const bNode *node);
+             const bNode *node,
+             const bNodeSocket *socket_out);
   virtual ~NodeParser() = default;
 
   virtual NodeItem compute() = 0;
 
  protected:
-  NodeItem create_node(const std::string &mx_category,
+  static std::string node_name(const bNode *node, const bNodeSocket *socket_out);
-                       const std::string &mx_type,
+  NodeItem create_node(const std::string &mx_category, const std::string &mx_type);
-                       bool noname = true);
   NodeItem get_input_default(const std::string &name);
   NodeItem get_input_default(int index);
   NodeItem get_input_link(const std::string &name);
@@ -45,6 +46,7 @@ class NodeParser {
   NodeItem get_input_default(const bNodeSocket &socket);
   NodeItem get_input_link(const bNodeSocket &socket);
   NodeItem get_input_value(const bNodeSocket &socket);
+  NodeItem compute_full();
 };
 
 template<class T> NodeItem NodeParser::value(const T &data) const
@@ -65,7 +67,6 @@ DECLARE_PARSER(InvertNodeParser)
 DECLARE_PARSER(MathNodeParser)
 DECLARE_PARSER(MixRGBNodeParser)
 DECLARE_PARSER(NormalMapNodeParser)
-DECLARE_PARSER(OutputMaterialNodeParser)
 DECLARE_PARSER(TexCheckerNodeParser)
 DECLARE_PARSER(TexEnvironmentNodeParser)
 DECLARE_PARSER(TexImageNodeParser)

source/blender/nodes/shader/materialx/nodes/normal_map.cc

@@ -2,6 +2,7 @@
  *
  * SPDX-License-Identifier: GPL-2.0-or-later */
 
+#include "../material.h"
 #include "node_parser.h"
 
 namespace blender::nodes::materialx {
@@ -9,11 +10,11 @@ namespace blender::nodes::materialx {
 NodeItem NormalMapNodeParser::compute()
 {
   std::string default_space = "object";
-  NodeShaderNormalMap *normal_map_node = static_cast<NodeShaderNormalMap *>(node->storage);
+  NodeShaderNormalMap *normal_map_node = static_cast<NodeShaderNormalMap *>(node_->storage);
   NodeItem color = get_input_value("Color");
   NodeItem strength = get_input_value("Strength");
 
-  NodeItem res = create_node("normalmap", "vector3", false);
+  NodeItem res = create_node("normalmap", "vector3");
   res.set_input("in", color.to_vector3());
   res.set_input("scale", strength);
 
@@ -29,8 +30,8 @@ NodeItem NormalMapNodeParser::compute()
       CLOG_WARN(LOG_MATERIALX_SHADER,
                 "Ignoring unsupported Space: %d %s (%d), %s will be used",
                 normal_map_node->space,
-                node->name,
+                node_->name,
-                node->type,
+                node_->type,
                 default_space);
   }
   return res;

source/blender/nodes/shader/materialx/nodes/output_material.cc

@@ -2,19 +2,56 @@
  *
  * SPDX-License-Identifier: GPL-2.0-or-later */
 
-#include "node_parser.h"
+#include "output_material.h"
 
 namespace blender::nodes::materialx {
+OutputMaterialNodeParser::OutputMaterialNodeParser(MaterialX::GraphElement *graph,
+                                                   const Depsgraph *depsgraph,
+                                                   const Material *material,
+                                                   const bNode *node)
+    : NodeParser(graph, depsgraph, material, node, nullptr)
+{
+}
 
 NodeItem OutputMaterialNodeParser::compute()
 {
-  NodeItem node = empty();
+  return empty();
-  NodeItem surface = get_input_link("Surface");
-  if (surface) {
-    node = create_node("surfacematerial", "material", false);
-    node.set_input("surfaceshader", surface);
 }
-  return node;
+
+NodeItem OutputMaterialNodeParser::compute(const std::string &socket_name)
+{
+  NodeItem surface = empty();
+  if (node_) {
+    surface = get_input_link(socket_name);
+  }
+  else {
+    surface = create_node("standard_surface", "surfaceshader");
+    surface.set_input("base_color", value(MaterialX::Color3(1.0f, 0.0f, 1.0f)));
+  }
+  NodeItem res = create_node("surfacematerial", "material");
+  res.node->setName(node_name(node_, nullptr));
+  res.set_input("surfaceshader", surface);
+  return res;
+}
+
+NodeItem OutputMaterialNodeParser::compute_default()
+{
+  NodeItem surface = create_node("standard_surface", "surfaceshader");
+  surface.set_input("base_color", value(MaterialX::Color3(material_->r, material_->g, material_->b)));
+  surface.set_input("diffuse_roughness", value(material_->roughness));
+  if (material_->metallic > 0.0f) {
+    surface.set_input("metalness", value(material_->metallic));
+  }
+  if (material_->spec) {
+    surface.set_input("specular", value(material_->spec));
+    surface.set_input("specular_color", value(material_->spec));
+    surface.set_input("specular_roughness", value(material_->roughness));
+  }
+
+  NodeItem res = create_node("surfacematerial", "material");
+  res.node->setName("Material_Default");
+  res.set_input("surfaceshader", surface);
+  return res;
 }
 
 }  // namespace blender::nodes::materialx

source/blender/nodes/shader/materialx/nodes/output_material.h

@@ -0,0 +1,22 @@
+/* SPDX-FileCopyrightText: 2011-2022 Blender Foundation
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later */
+
+#pragma once
+
+#include "node_parser.h"
+
+namespace blender::nodes::materialx {
+
+class OutputMaterialNodeParser : public NodeParser {
+ public:
+  OutputMaterialNodeParser(MaterialX::GraphElement *graph,
+                           const Depsgraph *depsgraph,
+                           const Material *material,
+                           const bNode *node);
+  NodeItem compute() override;
+  NodeItem compute(const std::string &socket_name);
+  NodeItem compute_default();
+};
+
+}  // namespace blender::nodes::materialx

source/blender/nodes/shader/materialx/nodes/tex_checker.cc

@@ -16,16 +16,11 @@ NodeItem TexCheckerNodeParser::compute()
     float v = scale.value->asA<float>();
     scale = value(MaterialX::Vector2(v, v));
   }
-  /* Modifier to follow Cycles result */
-  scale = scale * value(4.0f);
 
   NodeItem texcoord = create_node("texcoord", "vector2");
   NodeItem place2d = create_node("place2d", "vector2");
   place2d.set_input("texcoord", texcoord * scale);
 
-  /* TODO: fix offset:
-   * place2d.set_input("offset", offset); */
-
   NodeItem separate = create_node("separate2", "multioutput");
   separate.set_input("in", place2d);
   separate.add_output("outx", "float");
@@ -42,9 +37,9 @@ NodeItem TexCheckerNodeParser::compute()
   NodeItem ifequal =
       (modulo_x.floor() + modulo_y.floor()).if_else("==", value(1.0f), value(0.0f), value(1.0f));
 
-  NodeItem res = create_node("mix", "color3", false);
+  NodeItem res = create_node("mix", "color3");
-  res.set_input("fg", color1.to_color3());
+  res.set_input("bg", color1.to_color3());
-  res.set_input("bg", color2.to_color3());
+  res.set_input("fg", color2.to_color3());
   res.set_input("mix", ifequal);
   return res;
 }

source/blender/nodes/shader/materialx/nodes/tex_environment.cc

@@ -12,10 +12,10 @@ namespace blender::nodes::materialx {
 
 NodeItem TexEnvironmentNodeParser::compute()
 {
-  Image *image = (Image *)node->id;
+  Image *image = (Image *)node_->id;
-  NodeTexEnvironment *tex = static_cast<NodeTexEnvironment *>(node->storage);
+  NodeTexEnvironment *tex = static_cast<NodeTexEnvironment *>(node_->storage);
-  Scene *scene = DEG_get_input_scene(depsgraph);
+  Scene *scene = DEG_get_input_scene(depsgraph_);
-  Main *bmain = DEG_get_bmain(depsgraph);
+  Main *bmain = DEG_get_bmain(depsgraph_);
   std::string image_path;
   /* TODO: What if Blender built without Hydra? Also io::hydra::cache_or_get_image_file contains
    * pretty general code, so could be moved from bf_usd project. */
@@ -24,7 +24,7 @@ NodeItem TexEnvironmentNodeParser::compute()
 #endif
 
   NodeItem texcoord = create_node("texcoord", "vector2");
-  NodeItem res = create_node("image", "color3", false);
+  NodeItem res = create_node("image", "color3");
   res.set_input("file", image_path, "filename");
   res.set_input("texcoord", texcoord);
   return res;

source/blender/nodes/shader/materialx/nodes/tex_image.cc

@@ -12,10 +12,10 @@ namespace blender::nodes::materialx {
 
 NodeItem TexImageNodeParser::compute()
 {
-  Image *image = (Image *)node->id;
+  Image *image = (Image *)node_->id;
-  NodeTexImage *tex = static_cast<NodeTexImage *>(node->storage);
+  NodeTexImage *tex = static_cast<NodeTexImage *>(node_->storage);
-  Scene *scene = DEG_get_input_scene(depsgraph);
+  Scene *scene = DEG_get_input_scene(depsgraph_);
-  Main *bmain = DEG_get_bmain(depsgraph);
+  Main *bmain = DEG_get_bmain(depsgraph_);
   std::string image_path;
   /* TODO: What if Blender built without Hydra? Also io::hydra::cache_or_get_image_file contains
    * pretty general code, so could be moved from bf_usd project. */
@@ -24,7 +24,7 @@ NodeItem TexImageNodeParser::compute()
 #endif
 
   NodeItem texcoord = create_node("texcoord", "vector2");
-  NodeItem res = create_node("image", "color3", false);
+  NodeItem res = create_node("image", "color3");
   res.set_input("file", image_path, "filename");
   res.set_input("texcoord", texcoord);
   return res;

source/blender/nodes/shader/materialx/nodes/tex_noise.cc

@@ -18,7 +18,7 @@ NodeItem TexNoiseNodeParser::compute()
 
   NodeItem texcoord = create_node("position", "vector3");
 
-  NodeItem res = create_node("fractal3d", "color3", false);
+  NodeItem res = create_node("fractal3d", "color3");
   res.set_input("position", texcoord * scale);
   res.set_input("octaves", detail);
   res.set_input("lacunarity", lacunarity);

source/blender/nodes/shader/materialx/nodes/vector_math.cc

@@ -10,7 +10,7 @@ namespace blender::nodes::materialx {
 NodeItem VectorMathNodeParser::compute()
 {
   /* TODO: finish some math operations */
-  auto op = node->custom1;
+  auto op = node_->custom1;
   NodeItem res = empty();
 
   /* Single operand operations */