Ambient Oclusion render output strange behavior

[kubbek]

I noticed strange behaviour of the Ambient Oclusion render output. It reacts on scene lighting and I get good quality only with full lighting and GI enabled. I atached some examples - everywhere universal settings min 1 max 100 with noise threshold of 0.01. It should have the same quality everywhere, also with no lights at all but it looks differently in every lightin scenario.
Additionaly it reacts to frame buffer image adjustments like exposure, curves, white balance etc. That is not very convenient as it must now be saved separately with all adjustments turned off.

[kubbek]

Here clean example - physically based daylight turned on.

[vladimir.nedev]

I noticed strange behaviour of the Ambient Oclusion render output. It reacts on scene lighting and I get good quality only with full lighting and GI enabled. I atached some examples - everywhere universal settings min 1 max 100 with noise threshold of 0.01. It should have the same quality everywhere, also with no lights at all but it looks differently in every lightin scenario.

This happens because of the changes I made described here :
http://forums.chaosgroup.com/showthr...formance-issue

Since the AO subdivs get divided by the max image sampler subdivs (in your case 100) and since you don't have any noise in the main RGB element, both the image and the AO sampler take very few samples.

I've re-enabled AA for the Ambient occlusion render element in tomorrow's build ( 2015-10-22 ), you can manually disable it from the "Antialiasing" channel in the "Render Output" options.

Additionaly it reacts to frame buffer image adjustments like exposure, curves, white balance etc. That is not very convenient as it must now be saved separately with all adjustments turned off.

Do you think there might be a situation where you will want some of these adjustments applied to the Ambient occlusion element ?
We are thinking about disabling all VFB corrections, except sRGB, on all render elements, except the main RGB one.
This will affect V-Ray for Max/Maya as well.

Greetings,
Vladimir Nedev

[kubbek]

Thank you Vladimir, now it works as expected.

I don't think any render output other than the Final Color Output should be corrected by the framebuffers corrections. It is very easy to unintentionaly destroy this passes. Passes like AO have their own settings and don't need additional adjustments in framebuffer.

I asked for it a while ago but I will repeat it here as we talk about different render outputs. It would be very helpful if I could render chosen outputs like alphas and ao WITHOUT rendering final color output. Now I have to disable all lighting and GI to get decently fast render of this passes in complex scenes when I need to render them afterwards.

Best,
Jakub

[vladimir.nedev]

I asked for it a while ago but I will repeat it here as we talk about different render outputs. It would be very helpful if I could render chosen outputs like alphas and ao WITHOUT rendering final color output. Now I have to disable all lighting and GI to get decently fast render of this passes in complex scenes when I need to render them afterwards.

Well, I can make a "Render fast"(or Render AO, Alpha mask, etc... only) menu entry that will make the necessary modifications to the scene while exporting it.
The Final color output cannot be disabled in the V-Ray core, but like you said, materials can be changed to render very fast.
It should be easy to turn off GI, ignore all lights, turn on "Anti-alias masked alpha outputs" and change the materials to a simple light material.

But what happens if you have transparent materials, in this case the alpha element has transparency, but it will be lost with the light material ?
Do you have a solution for this, when you modify your scenes in this manner ?

Edit : transparency can affect the Ambient occlusion pass as well, I think.

Greetings,
Vladimir Nedev

[kubbek]

What I for now do is just disable lights, environment and GI and it works good enough. I do not change material settings though it could speed things up as you say. I have no realy satisfying solution for this. I just thought it should be simple to implement Anyway in modo it just works and it is very convenient. You just switch final color output and have lighting fast alpha render and so on.

[danielz]

This would be awesome.