Among the notable changes in Clutter 1.3.6 is a GLX fall-back for using the EXT_framebuffer_blit extension if the MESA_copy_sub_buffer extension is not available, using fragment shaders instead of texture combiners inside Cogl materials, a new design for materials have been implemented, a modified GLU tesselator is now used for drawing paths to a vertex buffer rather than the stencil buffer or scanline rasterizer, always use scissoring when clipping, the GL libraries are no longer included when using the EGL X11 back-end, and the EGL native and X11 back-ends have been merged together. There are also various other changes to be found in Clutter 1.3.6.
The release announcement for Clutter 1.3.6 can be read on clutter-announce. Clutter 1.4.0, which will be the first stable release to incorporate all of these Clutter 1.3 changes, will be released in time for the GNOME 3.0 release in September. Clutter is used within the Mutter compositing window manager found in GNOME 3.0 and is also used by various GNOME Games and other projects.