update readme

README.md

@@ -18,6 +18,18 @@ The original glm library is for C++ only (templates, namespaces, classes...), th
   </tbody>
 </table>
 
+##Features
+- general purpose matrix operations (mat4, mat3)
+- general purpose vector operations (cross, dot, ...)
+- affine transforms
+- optimized affine transform matrices (mul, rigid-body inverse)
+- camera (lookat)
+- projections (ortho, perspective)
+- quaternions
+- euler angles / yaw-pitch-roll
+
+<hr />
+
 This library is header only so you dont need link to application. All functions are marked inline (always_inline) so compiler probably will inline all these functions
 
 Most of math functions are optimized manualy with SSE2 if available, if not? Dont worry there are non-sse versions of all operations
@@ -25,14 +37,13 @@ Most of math functions are optimized manualy with SSE2 if available, if not? Don
 This library provides:
 
 - Simple usage
-- Small memory usage
+- Small memory footprint
 - The codes are small and more readable than C++ templates, metafuncs
 - Optimized operations with SIMD and non-SIMD
-- Small code size
 - All operations are inline (if compiler will do), no function call overhead
 - Chain matrix multiplication (square only)
 
-You can pass matrices and vectors as array to functions rather than get address. 
+You can pass matrices and vectors as array to functions rather than get address.
 
 ```C
   mat4 m = {
@@ -45,6 +56,16 @@ You can pass matrices and vectors as array to functions rather than get address.
   glm_translate(m, (vec3){1.0f, 0.0f, 0.0f});
 ```
 
+Library contains general purpose mat4 mul and inverse functions but also contains some special form (optimized) of these functions for affine transform matrices. If you want to multiply two affine transform matrices you can use glm_mul instead of glm_mat4_mul and glm_inv_tr (ROT + TR) instead glm_mat4_inv
+```C
+/* multiplication */
+mat4 modelMat;
+glm_mul(T, R, modelMat);
+
+/* othonormal rot + tr matrix inverse (rigid-body) */
+glm_inv_tr(modelMat);
+```
+
 ##License
 MIT. check the LICENSE file