REALLY slow rendering

Labello · Post by **Labello** » Mon Feb 18, 2008 6:22 am

hey out there...

there is a issue that is not logical to me... mybe you can help...

i have got a scene with two exit-portals and a very simple room. a sun outside and a ground to reflect some light into the room.

but when i export to indigo it renders just with 1k samples/second.

i'm pretty shure that it's my mistake but i'm not able to find it -.-* maybe someone out there is able to help!

Thanks a lot in advance

PS:i attached the .blend-file so u can reproduce the problem

Big Fan · Post by **Big Fan** » Mon Feb 18, 2008 8:52 am

ok some issues-
flip normals and remove doubles of room ( 8 )
cover both openings with portal planes
use bidirectional

Labello · Post by **Labello** » Mon Feb 18, 2008 8:58 am

thanks a lot! i will try!

Labello · Post by **Labello** » Mon Feb 18, 2008 9:22 am

the suggestions didn't work.

I am going to recreate the whole scene and will see whether the issue turns up again!

i'm getting bothered in a way!

zsouthboy · Post by **zsouthboy** » Mon Feb 18, 2008 2:27 pm

I see only one exit portal in the scene, and it's not in the right place (intersect and completely SEAL the interior with exit portals - the one i found is floating behind a window)

My render results, as you uploaded the file, are attached.

Switch to simple path tracing / MLT and the slowness disappears.

Bidir KILLS performance on this scene - odd. I've never seen this before.

psor · Post by **psor** » Mon Feb 18, 2008 2:41 pm

I tried the scene too. I found two exit portals in the blender file adjusted
both to intersect the windows slightly and scaled the windows a tiny bit
to close some very small openings. Then I deleted the plane "outside",
it's not needed and slows the rendering down, because rays bounce
around. When I did render I've got ~8k s/s.

Then I imported the scene into 3dsmax flipped the normals of the room,
scaled the room to fit 250cm room height, then I added a camera and a
sun and did render. Believe it or not I've got ~40k s/s.

nb: Both scenes where rendered using the same settings and are
rendered on an Athlon64 X2 4400+.

So something with the mesh seems to be wrong. I'm not familiar with
blender so I can't check whats going on there.

take care
psor

zsouthboy · Post by **zsouthboy** » Mon Feb 18, 2008 2:42 pm

When I delete all the faces from the bottom of your structure, the problem with BiDir goes away.

EDIT:

This must be a bug - take a look at my screenshots.

I removed the bottom portion of the mesh - the remaining floor is a simple plane.
Export without that plane - normal speed render.
Export with plane - SLOW render.

zsouthboy · Post by **zsouthboy** » Mon Feb 18, 2008 3:07 pm

I'm screwing with this scene still, trying to figure out if it's a normals issue or something else.

Taking the structure and extruding an outside (so that we've got polys with normals pointing outwards) to it doesn't fix the speed issue.

doublez · Post by **doublez** » Mon Feb 18, 2008 4:23 pm

All the faces are facing out because that's what ctrl+n does, so after you press ctrl+n press W->Flip Normals. Of course you need to have all verts selected while you do all this.

Big Fan · Post by **Big Fan** » Mon Feb 18, 2008 7:09 pm

ok sorry it didnt work for you earlier I was rushing to get to work else I would have given more time

here is what I did just now
its running on my old Pentium 2.66 pc at 22k
1. flip normals of room and remove doubles
2. deleted your portal planes ( I see you have 1 hidden already - I didnt notice this first time) and replaced with a portal cube closely encasing the whole room - normals inward
3. changed sky turbidity to be 2.2
4. deleted your outside ground plane
5. scaled your sun lit window frame to cover the opening entirely
6. changed to bidirectional
7.reinhard 10,2,3
8.max consec reject 1000 depth 1000

and for me it looks like this:

Post by **OnoSendai** » Tue Feb 19, 2008 12:47 am

The slowness problem may be due to too high albedo.
Make sure there is not too much white in room or reduce RGB values.

zsouthboy · Post by **zsouthboy** » Tue Feb 19, 2008 3:10 am

That was it, Ono!

It didn't even occur to me to check the albedo material.

It was 1,1,1 - obviously way too high.

Set to .8 .8 .8, and the render speed (with BiDir) is fine.

Kram1032 · Post by **Kram1032** » Tue Feb 19, 2008 3:15 am

the exit portals should be as simple and as small as possible, without showing any thing behind them, so, a cube around the whole room isn't too efficient, I guess....

(the smaller they are, the smaller is the area, where light has to pass... Which brings all the efficiency of exit portals.)

doublez · Post by **doublez** » Tue Feb 19, 2008 4:19 am

What exactly does an exit portal do?

Labello · Post by **Labello** » Tue Feb 19, 2008 4:50 am

so it was just the total white color of the material?

Edit: i deleted all stuff except the room and rendered from the outside but still crappy quality and slow rendering.

REALLY slow rendering

REALLY slow rendering

Who is online