Order of the Butterfly
Posts: 405 from 2003/7/25
I would like to ask about something regarding TinyGL because I probably something don’t understand.
I am talking about current final public version of TinyGL in MorphOS 3.17 which doesn’t support shaders (fixed pipeline). Please forget for a moment about amazing public beta-versions of TinyGL which have been released by Bigfoot. :)
There may be two reasons for low performance of a program which uses OpenGL 1.x (fixed pipeline) for rendering a graphics on screen:
1. Geometry of graphics is too high and CPU (in case of fixed pipeline) is not able to recalculate all transformations.
2. Huge polygons (especially with transparency) with big textures cause problems with fillrate performance.
I see that I can create very very simple geometry (which is not a challenge for 68040) with huge polygons for achieve low performance. In this case CPU gauge shows 100% usage. If I resize window from 1440x960 to 320x200, CPU usage is about 10-15%.
1. Is it normal situation that CPU usage is very high when geometry is extremely low but big polygons kill fillrate? Should I observe 100% CPU usage in this case? Should rendering of huge polygons (using 3d accelerator) influence very high to CPU usage?
2. Does CPU gauge in MorphOS shows only CPU usage or also GPU usage?
I don’t want to say that there is something wrong in TinyGL. I am sure it is not. :) I would like to increase my knowledge and understand something. I have already found somewhere a very old post (from fixed pipeline ages) where someone written that there is no general rules and it depends on gfx driver.
One more thing
I run examples from beta-versions of TinyGL NG wich support shaders. Why do I see 100% CPU usage if geometry is calculated by GPU, gfx is rendered by GPU. CPU should be unoccupied. Am I right? Of course, theoretically.. :)
I hope I was able to explain what I wanted using my English… :) :)
[ Edited by MDW 05.12.2022 - 19:08 ]