== Chimera Speed and Memory Use ==

What causes Chimera to run slowly or run out of memory?

 * [#GraphicsSpeed Graphics speed]
 * [#CalculationSpeed Calculation speed]
 * [#MemoryRequirements Memory requirements]
 * [#bit64 32-bit versus 64-bit Chimera binaries]
 * [#multicore Multi-core calculations]

== Graphics Speed ==

Why is rotating the scene slow?  Large molecules or volume data can cause display updating
slower than the normal 30 frames per second.

'''Graphics card.'''
Drawing speed is usually limited by the speed of the graphics card.
See the table of [wiki:benchmarks benchmark results] for different graphics cards running Chimera.
Chimera uses OpenGL for 3-dimensional graphics.  A card that is fast for playing video games is likely
to be fast for Chimera.  Integrated Intel graphics in laptops and desktops is usually slowest.
Graphics cards from Nvidia and ATI are common and work well.
On Linux installing a graphics driver is usually necessary.  If Chimera menu entry Help / Report a Bug
lists the OpenGL renderer as '''Mesa''' in the ''Gathered Information'' section then you need to install
a graphics driver.

'''Selected objects'''
The green outline around selected objects is created by drawing the selected objects 5 times.
If everything is selected than the rendering can be 5 times slower.

'''Transparency'''
Rotating large transparent surfaces can be slow.  For each orientation the triangles making up the
surface are sorted by depth and drawn in order from farthest away to nearest.  The sorting is done
on the CPU, not the graphics card.  The time to do the sorting each time the scene is redrawn often
limits the frame rate.

'''Molecule display styles'''
Displaying all atoms of a large molecule (e.g. 100,000 atoms) can cause slow rendering.
The ''wire'' display style is fastest, while ''stick'', ''ball and stick'', and ''sphere''
display styles are typically a 10 to 100 times slower.  Showing only the backbone of a protein
using ''ribbon'' style is faster than showing all atoms (except for ''wire'').  The Chimera
'''subdivision quality''' setting controls the smoothness of these molecule depictions and
higher values will cause slower display.


== Calculation Speed ==

== Memory Requirements ==

== 32-bit versus 64-bit Chimera binaries == #bit64

== Multi-core Calculations == #multicore