Preview Render incredibly slow (compared to 27.16)

[Andreas_Resch]

In the process of testing the isolated rendering of selected objects, it became clear that there are some serious issues with the refreshing of the scene while being in preview rendering mode. Compared to V27.16 there are staggering differences in how the scenes processing is handled. This certainly needs to be addressed. I have done two comparisons and record screencasts of them.

Here's the first test ...
*) Created an array of 2500 simple spheres
*) Converted them to a mesh
*) Separating them into individual objects
*) Toggle Local View ON
*) Toggle Local View OFF

In V27.16 all those steps are faster than in 28.5. But the worst part is when the preview updates after the spheres are separated. As you can see, there are only a few spheres rendered at a time. The sample count never goes above 1 until all the spheres have been gone through. And it gets even worse when I isolate the preview for the selected object. It takes about 4 minutes until the viewport is updated. And it takes another few minutes when you turn the local view OFF again. As you can see in the recording of the 28.5 version, I've eventually canceled the recording. But like in the separation it seems that only a few of the spheres appear at a time.

Here's the screencast video of the 27.16 version ... http://www.argfx.at/upload/Octane2716_A ... ate_01.zip
Here's the screencast video of the 28.5 version ... http://www.argfx.at/upload/Octane285_Ar ... ate_01.zip


Here's the second test ...
*) Switch to preview render
*) Switch back to solid mode

Here the situation is very bad as well. Switching the scene from above to preview mode takes almost 3 minutes in V28.5. In V27.16 the same process takes about 5 seconds. There's something wrong in the code here. Maybe the underlying problem to all the issues from above.

Here's the screencast video of the 27.16 version ... http://www.argfx.at/upload/Octane2716_S ... iew_01.zip
Here's the screencast video of the 28.5 version ... http://www.argfx.at/upload/Octane285_St ... iew_01.zip