MRay Daylight system and interiors

[saimirducellari]

Hello everybody.

I'm trying to make a sort of a simulation of a real lighting condition with MRay's Daylight system. I've imported and scaled my dwg, inserted the daylight system fixed the North direction and set up the location, time etc, etc. I inserted the daylight portals at every window and launched some test renders.

 

RESULT

 

NOT ENOUGH ILLUMINATION EVEN WHEN I INCREASE PHOTON'S ENERGY AND A SORT OF TOO BRIGHT AREA ON THE ROOF NEAR THE WINDOW WHERE ON MY THOUGHT IT SHOULDEN'T BE. (I'm attaching some img.)

If anybody can help me improve my work I'd be very grateful.

Thanks in advance.

Edited June 20, 2013 by saimirducellari

[Francisco Penaloza]

I think your illumination is pretty much where it should be, more bright accents should be done with artificial lights, lamps and so. IF you want brighter interior you can lower your exposure a little more, but you can adjust that in Photoshop too.

Do you have a ground plane under your room? this is important to get the right right also. there is one room that I see something strange on the ceiling, first check your mesh, if there is any gasp or flip polygons, and then you can try to reduce your Photon size, you may need to increase the photon count to compensate, but for this scene I would try only Final Gather I think it should be fine.

 

http://imtex.org/wp-content/uploads/loft-condo-interior-design-small-apartment-decorating-ideas-5-foto-image-01.jpg

[Corey Beaulieu]

I think It looks pretty close to correct. Or at least close to what I would expect. You could likely adjust your camera exposure just a little more because the windows should be blown out more than they are for an interior camera.

 

(http://www.interior-photography.net/wordpress/wp-content/upl/IMG_1554.jpg)

 

Also, Do you have a ground plane in your scene? If not, this will help bounce light into your image.

[Corey Beaulieu]

Haha... I forgot to hit "post" and it looks like Francisco was typing the same thing as me... I guess great minds think alike huh, Francisco?

[Francisco Penaloza]

LOL

it would be very freaky if you post the same image ha ha ha.

but yes you are right with your comment

[Justin Hunt]

Also make sure you have set the photon emit radius for the sun to be just big enough to fit the windows.

[Cesar R]

I think It looks pretty close to correct. Or at least close to what I would expect. You could likely adjust your camera exposure just a little more because the windows should be blown out more than they are for an interior camera.

 

(http://www.interior-photography.net/wordpress/wp-content/upl/IMG_1554.jpg)

 

Also, Do you have a ground plane in your scene? If not, this will help bounce light into your image.

 

 

Just to learn some thing new here, what do you guys mean by does he had a ground plane in the scene?

[matthewgriswold]

A simple plane outside of the space that can bounce light up into the scene...otherwise photons + light will shoot beyond the scene, to nowhere.

 

*Edit* I'm a visual guy, so here are three images showing what a ground plane can do with the different surfaces in a MR scene.

Edited June 21, 2013 by matthewgriswold

[saimirducellari]

Thanks to everybody for your reply. Yes I forgot my ground plane.... well maybe I didn't insert it because the flat is on the 10th floor but I guess this is not important I have to add it. Can you help me with some indications or the link of some tutorial on how to check for "gasp or flip polygons" I don't even know what they are, never had this kind of problem....my scene is .dwg composed of solids (extruded objects).

 

I may be wrong but the problem with the ceiling regards all images....I don't think in a real situation the light on the ceiling near the window could be like that. Well maybe if my windows touched the ceiling the render would be correct but not in my case I think. I'll try to see what happens adding the ground and rendering with final gather and I'll let you know.

Thanks again

Edited June 21, 2013 by saimirducellari

[CJI]

What Francisco means is to check for any gaps in your geometry. It needs to be tight and closed so light cant leak through, same goes for flipped normals. Mental ray cant read both sides of a polygon by default unless you tell it too through the shaders etc. So if light and photons hit the backface of a polygon they will just travel through it as though it wasn't there, the is the same for the camera, it may not "see" the polygon in the render if its back face is to the camera. The solids from the dwg are just faces that form a 3 dimensional shape, they are not actually "Solid" so if one of these is the wrong way round you need to flip it using the editable poly object/modifier.

 

As the guys have said the lighting doesn't seem a million miles away from where we would expect it to be. If you are describing the light cast on the ceiling, i think its a by product of the portal lights shunting the daylight from outside through the windows as final gather isn't very efficient at pulling light through these openings. At least that's what i think is happening.

[saimirducellari]

Well Curtis you are right about the light on the ceiling, it is a product of the light portal and final gather. Without final gather though the result is worst. Yes 3D max trasforms solids in boxses but I thought it flips automatically the normals. I will check and let you know.

[CJI]

Sorry for any confusion, I wasn’t suggesting you not use Final Gather.

 

Sometimes when importing any format I have found that there can be occasional problems with normals so its always wise to check.

[saimirducellari]

Don't worry no confusion. I just confirmed what you said about portals and final gather and since I'm trying to figure out how to obtain the best results I'm 'simply writing down everything that passes on my mind in order to extend the discussion. Thats what forums are forn arten't they.

[Cesar R]

thanks for the information. So I guess I was always missing an important part of the recipe.

[saimirducellari]

Well normals, ok. No gasps or spaces between vertical and horizontal objects but still the same problems with the light.....Can anyone help?

[Matt McDonald]

turn off FG and let's see what just the GI is doing. Or, here's a good tutorial for getting interiors lit with the daylight system to turn out correctly.

 

http://jeffpatton.net/2011/11/mental-ray-physical-sky-tips-for-architectural-interiors/

[Cesar R]

thanks for sharing, I hope its helpful to the OP.

[saimirducellari]

Here is the link to the img with FG off. I guess I have too much energy on those light sources. I will try to decrease and let everybody know.

http://db.tt/SYtFB8iE

[saimirducellari]

here we go with the no FG render... I guess I have to much photon's energy in my schene so I switched off portals and decreased photons energy, than I fixed the light amount with envrionement control. after decreasing the photons radius I had a strange result (boo.jpg)...I guess the bright area on the ceiling is the reflection of the sunlight.

[CJI]

That is a pretty clean photon map there! I personally have never used it to create a clean image on its own before as its so much quicker and better result with FG.

 

I think what Matt was looking for when he said no FG was so we could see what the secondary bounces of GI were doing before final gather clean up. It generally looks like loads of overlapping polka dots and is a great way of trouble shooting what the photons are doing. Yours is seriously smooth so im guessing you have a high (or default) sampling radius so they have all merged together. Could you maybe post an image of your render settings?

[saimirducellari]

here you go with my GI settings.

[Francisco Penaloza]

did you received the file I send you?

The photon Radius is too big, this will give "clean" solution but, it will generate those bright areas in corners and will no produce any details. as Curtis mentioned a good solution of Gi will be hundreds or thousand of polka dots all around your scene, if you want more bright dots you need to decrees the Decay value, instead of increase multiplier.

I'll recommend to visit Jeff Patton website he has very good Tutorials explaining how FG and Photon map works.

[Cesar R]

Francisco, thank you make the post above. As it was what I had learned years ago. The good result of the OP were making me question this.

I have to say that 5.0m photons is what is also probably making the renders look a little flat?

[saimirducellari]

Yes Francisco I recived the file...it looks almost perfect thanx.