Document what to expect in terms of trace size and CPU overhead.

See also issue #146.

diff --git a/BUGS.markdown b/BUGS.markdown
index 09811332e763cfd3d1686dfda58d8440f32d1487..0c963f11a37befaf0b6be61eba437f67ad4df54b 100644 (file)
--- a/BUGS.markdown
+++ b/BUGS.markdown
@@ -50,12 +50,29 @@ Tracing
   There is no way to distinguish the fake calls from those actually
   made by the application yet.
 
   There is no way to distinguish the fake calls from those actually
   made by the application yet.
 

+* Huge traces will be generated for applications that make extensive use of
+  immediate mode drawing (ie., glBegin/glEnd), use vertex/element arrays in
+  user memory, or generate a lot of dynamic vertex data per frame.
+
+  However, this should not be a problem for modern OpenGL applications that
+  make an efficient use of VBOs and vertex shaders.
+

 * On MacOSX, the internal OpenGL calls done by GLU are not traced yet.
 
 
 Retracing
 ---------
 
 * On MacOSX, the internal OpenGL calls done by GLU are not traced yet.
 
 
 Retracing
 ---------
 

+* Replaying can take substantially more CPU due to the overhead of reading the
+  trace file from disk.
+
+  However, the overhead should not be significant for modern 3D applications
+  that do efficient use of VBOs and vertex shaders.  The communication between
+  CPU to GPU can easily be a bottleneck on the powerful discrete GPUs of
+  nowadays, and trace overhead tend to be propotional so it is not a
+  coincidence that applications that are optimized for modern GPUs will also be
+  traced and replayed efficiently.
+

 * glretrace needs to infer window sizes from glViewport calls, because calls
   that create/resize windows happen outside of OpenGL and are not traced.
   Therefore window will be missing if the application relies on the default
 * glretrace needs to infer window sizes from glViewport calls, because calls
   that create/resize windows happen outside of OpenGL and are not traced.
   Therefore window will be missing if the application relies on the default