Scene optimizing

[Hadi]

Hi guys, this is my first post on my first project with Corona after many years of V-Ray.
As per topic title, I'm struggling to get some decent render times with Corona 1.7. I attached a screen grab of an actual render from my scene in 6k.
I watched the newbie video of the mistakes to avoid when switching to Corona. So:

- White objects with an albedo of 200 maximum
- Portals capping perfectly every holes in the scene
- Corona Sun + Sky
- Default Settings
- There's Corona displacement on the bricks behind the render and on 3 towels
- Forest Pack green wall, as you can see from the picture, which is likely to slow down the render obviously
- All the bitmaps converted to Corona bitmaps
- All the normals imported with the correct gamma
- The glass shader used for the windows is standard, with no caustic ticked on
- I'm using the 3ds max built in camera, with photographic exposure and in-camera DOF

As you an see from the screenshot, after 9 hours of render on a machine with 88 threads, the noise amount was still 9%.
I think there's definitely something wrong. If it could help, I am able to send the scene over for testing.
Thanks.

[Philip kelly]

I know the feeling.

Can I ask have you rendered the scene with out the vegetation, and see what the outcome is?

[Hadi]

No, not yet. I was planning to do it tonight, as now I need the machine to work.

[maru]

Something is definitely wrong. This is a relatively simple scene, so should render faster.

Some ideas:
-the glowing objects to the left, over the window, and the yellow lamps - how are they made? Maybe you are incorrectly using light/light mtl/self illumination? Check out https://coronarenderer.freshdesk.com/support/solutions/articles/5000515603
-the glass on the lamps - are you sure caustics are off? can you switch to thin glass mode?
-the window glass - can you switch to thin glass mode?
-portal - can you check if it does not render faster without it? maybe the portal is intersecting with something, like the window glass?
-materials - try simplifying them, make sure the plants are not using refraction at all, but translucency

[Hadi]

Thanks for your reply Maru. So:

- You can check from the screenshots how the lamp bulbs are made. The left grey shape is the outside thin object, the right one is the inside thin object. I guess I can remove the inner shape and set the materials to thin? Then they have a corona light material applied to the geometry that it's supposed to cast light.
- caustics are off from the glass material as you can see from the screenshot.
- Yes I guess so.
- didn't try without. You can check from the screenshots how I set this up. From the close up you can see that I have that chamfer detail on the concrete before the portals, which I don;t know if it's creating any issue. Also, should I put portals on all the openings or just on one?
- There's no refractions at all on the plant, just translucency. All the materials are using the PBR mode, with no reflection map in the reflection slot. Only exception for the leaves, that have PBR mode on, but a reflection map as well.

[James Vella]

check 2 addional things on your plants should speed up quite alot

- bitmap blur is 1.0 not 0.1
- opacity maps are on "Clip" and no filtering in the bitmap option

[agentdark45]

2 things I've spotted:

1. You are using a complex light filament object as a main light source. I would make this object a self illuminating material and add a fake hidden corona light to give off the majority of the light from the bulb.
2. The light material is travelling through a thick glass bulb. Perhaps try adding a rayswitch material on the glass bulb material with an no material in the GI slot.

[maru]

Most probably that glowing light filament is the issue. Give it a self illuminated material or a light mtl with "emit light" off, and add a simple fake light as agentdark advised.

[Hadi]

Ok, thanks guys.
I'll try all the suggested advices in a bit. Should I add the fake Corona light inside the bulb or outside?

[maru]

Outside will be definitely safer. :)

For a start you can place some super simple spherical corona lights just below the light bulbs and see if there is a difference.

[Hadi]

Ok, quick test done.
I changed the bulb glass to a thin mesh with a glass material with the thin option ticked on.
Estimated time dropped from 40 hours to 21.
Then I tried again with all the artificial lights hidden, but it didn't change anything.
So it's either the vegetation or the portals.
As I asked before, do you guys usually use portals just on one opening or on all of them?
Another thing that popped in my mind is that I have a glass with glossy refraction behind the camera, set up like you can see in the screenshot.
Can that be one of the problems?

@James Vella - with no filtering in the opacity map, you mean blur to 0.01 for the opacity maps?

[romullus]

Filtering of opacity maps is disabled globally by default. If you didn't mess with dev/debug settings, you can worry not about it. Usually it is a good idea to clip opacity maps in the material, just don't expect huge speedup if your opacity maps are made decently. As for texture filtering bluring, that shouldn't have measurable effect in Corona 1.x and higher. And it won't have any effect on opacity maps anyway, since filtering for those maps are disabled.

AFAIK, portals should be added to all major openings or not to be added at all.

[Hadi]

Ok, so after few tests we are now sure that the problem is with the green wall.
Without it a get an estimated time of 2 hours 40 minutes for a 6k which is ok. Adding the clip options on the opacity maps definitely helped, but I still get too high render times.
I posted 2 screenshot of the foliage shaders, nothing fancy, but if someone could help me to spot any error within could be great.
I showed how I set up all the opacity maps as well, linking them to a forest edge node that allows me to use the edge mode within forest object to have a clean cut of the edges.

[PROH]

Hi. I would definitely make a test with the forest edge mode turned OFF. I believe I read somewhere that this could slow things down considerably. But can't find it ATM and not sure if it's still so. But anyway... I would make a test without it, to see if this is the "killer" or not.

[James Vella]

Filtering of opacity maps is disabled globally by default...

thanks for clarifying the filtering, I remember reading this but glad to hear it verified.

...@James Vella - with no filtering in the opacity map, you mean blur to 0.01 for the opacity maps?

Change this to 1.0 on all the maps for the vegetation if they have been changed - usually the diffuse map is the killer one for this.

Bitmap 0.1 filtering blur is great for things like floorboards where you want to see the texture on grazing angles perfectly, however on leaf maps its generally a bit over kill unless its a hero tree right next to the camera.