Update README.md

README.md

@@ -1,4 +1,58 @@
 Sirit
 =====
+A runtime SPIR-V assembler. It aims to ease dynamic SPIR-V code generation
+without calling external applications (like Khronos' `spirv-as`)  
 
-A dynamic assembler for SPIR-V.
+Its design aims to move code that does not belong to the application in the
+library without, limitting its functionality.
+
+What it does for you:
+* Sort declaration opcodes
+* Handle types and constant duplicates
+* Emit SPIR-V opcodes  
+
+What it will try to do in the future:
+* Add capabilities automatically
+* Optimize code
+
+What does not do for you:
+* Avoid ID duplicates (emitting the same instruction twice)
+* Dump code to disk
+* Handle code blocks/branches
+* Compile from a higher level language
+  
+  
+It's in early stages of development, many instructions are missing since
+they are written manually instead of being generated from a file.
+
+Example
+-------
+
+```cpp
+class MyModule : public Sirit::Module {
+public:
+    MyModule() {}
+    ~MyModule() = default;
+
+    void Generate() {
+        AddCapability(spv::Capability::Shader);
+        SetMemoryModel(spv::AddressingModel::Logical, spv::MemoryModel::GLSL450);
+        
+        auto main_type{TypeFunction(TypeVoid())};
+        auto main_func{Emit(Function(TypeVoid(), spv::FunctionControlMask::MaskNone, main_type))};
+        Emit(Label());
+        Emit(Return());
+        Emit(FunctionEnd());
+
+        AddEntryPoint(spv::ExecutionModel::Vertex, main_func, "main");
+    }
+};
+
+// Then...
+
+MyModule module;
+module.Generate();
+
+module.Optimize(2);
+std::vector<std::uint8_t> code{module.Assembly()};
+```