runelore Posted May 31, 2011 Share Posted May 31, 2011 (edited) Hi guys, I have a very strange problem which I simply cannot get rid of. Basically when ever I render anything with mirrors (100% reflections) in the scene, the irradiance map samples just go crazey and the reflected surface has like 100x more samples than any of the rest of the scene. This causes the mirrors to take massively more time than the rest of the frame to calculate. I am not talking just a little longer, I mean it makes the frame take 10 or 20 times longer than normal to calculate. The final results are fine but it is just an issue I need to get around as I have a big residential project coming up and will have a lot of mirrors to deal with!! I have attached a couple of images showing how many more samples there are in the mirror compared to the wall next to it. The rest of the scene renders perfectly and I am happy with the look but the time the mirrors take to render are crazey..! Any help would be greatly apprectiated! Cheers - Mo Edited May 31, 2011 by runelore Link to comment Share on other sites More sharing options...
matthewgriswold Posted May 31, 2011 Share Posted May 31, 2011 Do you have Reflective GI caustics enabled? Might turn that off if you can live without it. Link to comment Share on other sites More sharing options...
runelore Posted May 31, 2011 Author Share Posted May 31, 2011 Hi, Many thanks for your response. I havent got any caustics enabled at all and I am just using Refractive GI for the Global Illumination. I tried ticking Reflective GI also and that made no difference at all Thanks Link to comment Share on other sites More sharing options...
matthewgriswold Posted May 31, 2011 Share Posted May 31, 2011 hmm, sorry I can't help. Link to comment Share on other sites More sharing options...
runelore Posted June 1, 2011 Author Share Posted June 1, 2011 No worries Matthew, thanks for trying anyway! I was really hoping someone on here would have an answer to this, it is driving me mad! lol Link to comment Share on other sites More sharing options...
Brian Smith Posted June 1, 2011 Share Posted June 1, 2011 You have some settings that I think are unnecessarily high. The one i would change the most is the Adapt amount. A value of 0.6 is really low and makes adaptive settings less adaptive. If you went to the extreme and took it to 0.0, then every adaptive settings would basically become brute force and your Noise threshold would be rendered meaningless. I suggest using 1.0 and drop down to say 0.85 only when noise develops that you can't remove otherwise. HDRIs are an example of when you would want/need to drop this down...but definitely not to what you have now. Your Adapt DMC Max value is way high for your needs...although with a Color thresh value of 0.005, anything over 6 or 7 is probably ignored. You'd have to drop it to 0.003 or 0.002 to actually make it use that Max value. Regardless, try 2 of Min and 5 for Max with 0.005 for Clr thresh. Increase to 3/6 and 0.003 if and only if there is a noticeable benefit. As for the irradiance map, i'd keep it simple and use a high preset, and use 20-30 for HSph subdivs and 50-100 for Interp samples. Since reflected surfaces are handled by the primary bounce engine, the light cache means nothing. I'm also wondering if you have put a little blurriness on the mirror and if your subdivs value for the material is excessively high. If so, use a value around 20-30. Regardless, there's no reason you should be getting a 10x increase in render times regardless of how high your sampling is on the mirror. hope that helps. Link to comment Share on other sites More sharing options...
notamondayfan Posted June 1, 2011 Share Posted June 1, 2011 Is the reflective part of the mirror part of the glass object (ie just a multisub material on one object) or is the reflective part a separate object behind the glass? Link to comment Share on other sites More sharing options...
runelore Posted June 2, 2011 Author Share Posted June 2, 2011 Hi, thanks for the replies guys, hopefully still gonna get this resolved. The refractive part of the mirror is the same object, basically I have attached an image in the original post showing the mirror, it is a bevelled box with all sides as glass except the back face which is the reflective surface (No glossiness to it, just 100% reflective). As per the rendering settings, many thanks for taking the time to look through my settings. I will take those changes on board and give them a try! To be honest, even with the settings I had, the render times are still great at only an hour or 2 for the final images which is VERY acceptable, but no matter what I set them to, that damn mirror still takes 10 x longer to do the irrad map than the rest of the scene, it just seems to multily the samples like mad for some reason, I have always had this issue when rendering mirrors, not sure why! maybe it is because I do it as 1 object, I will take a look at separating the reflective face from the glass... again, guys, many thanks for your responses!! Cheers - Mo Link to comment Share on other sites More sharing options...
notamondayfan Posted June 3, 2011 Share Posted June 3, 2011 Just try modelling the glass and the reflective part separate, with a tiny gap between them both. I don't know if this will solve the problems, but from experience, I would model things with a glass part separately, as it's more accurate and it's how these things are made in the real world. Link to comment Share on other sites More sharing options...
Brian Smith Posted June 3, 2011 Share Posted June 3, 2011 those images shouldn't take more than 5-10 mins on a decent machine at around 1500 pixels. if you are getting 2 hours, you should do a lot of optimizing Link to comment Share on other sites More sharing options...
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