caicedor Posted February 2, 2009 Share Posted February 2, 2009 Well, finally opening my first thread. Its about a test I'm working on, where I try to have illuminated interior scenes using only vray sun and sky. Light is suposed to come in trough windows in the model, and it does. The problem is that I get to little gi in the interior model. I have tried deleting windows and, with no gi the result is pretty the same than using transparent windows. When I turn on gi, the interior scene is a lot much more illuminated. Somebody can explain this to me, I mean, why there is such a big difference and is there any way to work on it?? Hope tomorrow I can post pictures of what I'm talking about and glass material specifications... Link to comment Share on other sites More sharing options...
Ky Lane Posted February 2, 2009 Share Posted February 2, 2009 Someone correct me if Im wrong here.. GI is just faking what the window light source would do in the real world - which is bounce a million times off everything in your scene, and give a gentle general illumination. Rather than let your render engine calculate every single bounce etc, GI just fakes it to give it a nice feel. GI is good, if its too bright, you;'ll need to work on the intensities and exposures. Link to comment Share on other sites More sharing options...
caicedor Posted February 2, 2009 Author Share Posted February 2, 2009 Hey man, thanks for your answer. That's fast!! I think I have to ezplain my issue better. I have a little building model iluminated with vray sun and sky. Exteriors are fne, so I go interior. I supose light come in trough windows, using glass material applied to a 3mm box. I first start testing render with no gi, and I get a darl image were I can see light coming in. No gi, so image is dark. Then, I erased windows at all and get a little bit more illuminated scene, but no big difference. Then I undelet windows, turn on gi and get almost no improvement in lighting, I mean, very short gi. Finally, I erase again windows and render with gi on, I get a much more better iluminated scene. Now the question is. Why is there is so little difference when rendering no gi lights between scenes where windows present and erased? Why is there such a big difference when render with gi on between scenes where windows are present and erased?? As I said before, I hope tomorrow I can post pictures so you can better understand what I'm talking about!! Really thanks for your answer!! Link to comment Share on other sites More sharing options...
Ky Lane Posted February 2, 2009 Share Posted February 2, 2009 I think I get it. Are you using the same camera exposures for the interior, as the exterior? Link to comment Share on other sites More sharing options...
caicedor Posted February 2, 2009 Author Share Posted February 2, 2009 Not really, I'm using in a vray physical camera in both, but I've tweaked the interior one so I can improve the exposition. The thing I don't understand is why is there so little gi when the light comes in through the windows? Its like the light bounces much more when it comes directly (windows erased)... Link to comment Share on other sites More sharing options...
Ky Lane Posted February 2, 2009 Share Posted February 2, 2009 I havent used Vray in a long time, so my syntax is limited. You can up the GI bounces... I cant remember where. hopefully a Vray person will share. It defaults at 1, but you can up it alot. Link to comment Share on other sites More sharing options...
caicedor Posted February 2, 2009 Author Share Posted February 2, 2009 Yeah, and I think that the pictures will help a lot too!! The darkness of my pictures doesn't really matter... I'm trying to understand how is light behaving so I can know what I can do with that behavior Link to comment Share on other sites More sharing options...
Ky Lane Posted February 2, 2009 Share Posted February 2, 2009 Might just be your material. Try applying it to a plane instead of a box, and see what happens? Link to comment Share on other sites More sharing options...
caicedor Posted February 2, 2009 Author Share Posted February 2, 2009 Maybe, ill try tweaking it and let you know what happens... Thanks for your time and your will!! Link to comment Share on other sites More sharing options...
Ky Lane Posted February 2, 2009 Share Posted February 2, 2009 No worries mate. Im no Vray expert, but we can both play and learn while we wait for someone who knows what theyre talking about pipes in Link to comment Share on other sites More sharing options...
caicedor Posted February 2, 2009 Author Share Posted February 2, 2009 Well, I've been doing some research and I think that I have already followed the recomendation for galss materials to let the light come through it. As a matter of fact, in my model light is already coming through my glasses. If I compare my renders done with no global illumination, one with windows and the other with holes in the walls and no windows, the like is pretty much the same... And that's what I can't understand!!! Because if I do the same renders but with gi on, if the windows are present I get almost no light improvement, but if windows are deleted, light bounces much more!!! I'm feeling really frustrated for not carrying those pictures with me!! Link to comment Share on other sites More sharing options...
Ky Lane Posted February 2, 2009 Share Posted February 2, 2009 Maybe a skylight portal? Link to comment Share on other sites More sharing options...
Stephen Thomas Posted February 2, 2009 Share Posted February 2, 2009 A picture tells a thousand words... If I understand you correctly your window glass is blocking light from entering the room. This is probably because you haven't checked the 'Affect shadows' box on your glass material. If you do that then the light will be affected by whatever refraction value you have. Otherwise you can go to the glass objects properties and uncheck 'Cast shadows' to not have the glass affect the light coming in at all. Link to comment Share on other sites More sharing options...
caicedor Posted February 2, 2009 Author Share Posted February 2, 2009 Thanks Stephen, that's what I think to. I've done the cast shadows thing and got good results. Wath ior should I use to let all the light through my glasses to simulate like there is no glass at all?? Like in 1 hour ill be at work and will be able to post the photos Link to comment Share on other sites More sharing options...
Stephen Thomas Posted February 2, 2009 Share Posted February 2, 2009 IOR only affects how much the light rays are bent as they pass through the glass, it doesn't affect the amount of light getting through. The colour of your refraction slot (or fog if you're using it) will determine how much light passes through and whether it gets tinted a particular colour. Generally I don't use fog for architectural glass as I feel it is better suited to objects which vary in thickness. I do like my glass to cast a faint shadow and give the light a slight colour tint though, so my standard material setup would be: diffuse = black; reflection = white; refraction = h-100, s-5, v-240; ior = 1.6, fresnel ticked; affect shadow and affect alpha both ticked. Link to comment Share on other sites More sharing options...
caicedor Posted February 2, 2009 Author Share Posted February 2, 2009 Next, photos ive been talking about... They are very dark but thats not the problem. See the slight difference between renders with no gi. On have transparent glasses, the other only has holes in the walls. In the renders with gi, the difference becomes a lot much more evident!!! Why is that big difference coming in?? ALso mi glass matieral props. Link to comment Share on other sites More sharing options...
caicedor Posted February 2, 2009 Author Share Posted February 2, 2009 Ive bei doing tests and theres no difference in the ilumination. Does anybody knows how to get the ilumination in the scene with no windows, but having windows??? I can achieve that with no cast shadows, but i would like to know if its possible just changing the glass material properties... Also a little explanation about whats going on, so i can understand what vray is doing to get the results you can see in my previous post. I am including a test i have made aplying materials and with a better render. In all cases im using only vray sky, vray sun and physical camera... Link to comment Share on other sites More sharing options...
caicedor Posted February 2, 2009 Author Share Posted February 2, 2009 (edited) Hey guys, im really happy!!! I have found the answer to my questions. All i had to do to get the light coming through the windows bouncing inside my scene was turn on caustics reflactions!!! Im posting the images. All of them have gi tunrned on. The first has caustics refractions off, the other has caustics refractions turned on, and the last one has caustics rafractions turned off and windows are erased... Thanks to all of you for your answers!!! Edited February 2, 2009 by caicedor Wrong images.... Link to comment Share on other sites More sharing options...
Devin Johnston Posted February 2, 2009 Share Posted February 2, 2009 I think you have several issues here, first your camera settings should be adjusted properly for the type of space your in, if the room is to dim it might not be the light it might just be the camera. Second the position of the sun can dramatically change the light levels in the room, you should play with this. Third GI affects indirect light not direct, so if there is little direct light entering the room it will be naturally dark, if there is a lot then it will be brighter. Caustics will help a little bit but they shouldn’t be used to lighten up a scene, they are mainly an effect and will cause your render times to go up. The kind of color mapping your using can also affect how light or dark your image looks. Personally I don't think you have a "light" or "GI" problem I think your color mapping and camera settings are the issue. Link to comment Share on other sites More sharing options...
caicedor Posted February 2, 2009 Author Share Posted February 2, 2009 Thanks for your comments. Well, i think youre right. The best way to adjust poorly lit scenes is adjunting exposure and camera settings in this case. But as you can se the images in my previous post, ist evident that when i tunrned on refractive caustics, the global illumination solution found much more light bounces inside the room... If this causes more rendering times or some other issues, thats something to consider when you do your renders. For now, what i have realized is that refractive caustics have lit my scene lot more. Remember that all my pictures have been gottem with the same exposure and camera specifications. If you see the entire thread, you can see that if i turn on gi, and render two identical scenes, only different in the presence of absence of windows (holes on the wall with no material or a thin box aplied a glass material to simulate windows), the one with windows almost wont get lit by gi, and the other does. Now, if i turn on refractive caustics to render, the scene with windows get light from the gi solution, and it seems very like the scene where i erased my windows and let the light come in directly... Maybe its not practical to do this, but i think its how the reality behaves... And surely has helped me to understood a little bit more how does vray does its job!! Link to comment Share on other sites More sharing options...
tarmac Posted February 3, 2009 Share Posted February 3, 2009 hi people, about the gi i'm the same train that u both,so i cant help you. about vray do anyone of you know how to render wood ( the one that's in sketchup ) and mantain the texture ? of course adding a litlle brigth ... because when i do it , the final result have only one colour. thanks Link to comment Share on other sites More sharing options...
tarmac Posted February 3, 2009 Share Posted February 3, 2009 the texture in the picture is the one i'm talking about in this scene i've just added some light from the exterior but didn't render the floor if u could help me i would be very thankfull Link to comment Share on other sites More sharing options...
caicedor Posted February 3, 2009 Author Share Posted February 3, 2009 i dont understand what are talking about... The image you´ve posted, how did you do it?? because i can see the wood there... Link to comment Share on other sites More sharing options...
tarmac Posted February 3, 2009 Share Posted February 3, 2009 hi caicedor yes i know the texture is there, but in this one i have not add material or texture to the floor wath i mean is , to render this floor with bright, and reflections u understand ? this is standard what i wish to do is the result of the next picture that i've downloaded from the net sorry the english ( i'm portuguese ) do u think u can help me? Link to comment Share on other sites More sharing options...
caicedor Posted February 3, 2009 Author Share Posted February 3, 2009 Well, lets see if i have understood... You already have a material that you have put in the floor, but you want to get some reflections on that material, im right?? If you are using a vray material, then you have to give it some reflection value... Put a gray - white color in the material reflections color option, and render. Are you using vray renderer and vray materials?? Link to comment Share on other sites More sharing options...
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