beeemtee Posted March 2, 2007 Share Posted March 2, 2007 Since it's my first post on OdForce i would like to greet the members of the community! My question is, how could i do motion blur behind transparent objects? Here is what i get with standard shaders (vex_glass for the transparent object): Is this behaviour caused by some wrong settings, or i shoud write or build a custom shader to reach the expected result? I don't want to loose the distorsions of refraction, thats why i don't want to do it in composition. Thanks in advance: bmt Quote Link to comment Share on other sites More sharing options...
stevenong Posted March 2, 2007 Share Posted March 2, 2007 Hi bmt, The problem is with the VEX Glass shader. If you replace the shader with the VEX Super Material without any refraction, for example, you'll see that motion blur works. Unfortunately, you'll have to either write your own shader or do a comp trick. Someone else might have a solution for you but I can't think of any at the moment. Sorry. Cheers! steven Quote Link to comment Share on other sites More sharing options...
Dennis Sedov Posted March 2, 2007 Share Posted March 2, 2007 Since it's my first post on OdForce i would like to greet the members of the community!My question is, how could i do motion blur behind transparent objects? Here is what i get with standard shaders (vex_glass for the transparent object): Is this behaviour caused by some wrong settings, or i shoud write or build a custom shader to reach the expected result? I don't want to loose the distorsions of refraction, thats why i don't want to do it in composition. Thanks in advance: bmt Don't know exactly what is causing it, but it has something to do with raytracing. Maybe the depth of rays, because for one thing the shadow from the glass should be much more transparent, and since it is not you are either using depthmap shadows, or your raytracing settings have something missing. That is definately has nothing to do with shaders, so play with render settings rather. 100% it is raytracing issue! Quote Link to comment Share on other sites More sharing options...
edward Posted March 3, 2007 Share Posted March 3, 2007 You owe it to yourself if you haven't used Mario's glass shader. Get it Glass_Part4.zip from this post here: http://forums.odforce.net/index.php?showtopic=4196&st=36 I'm absolutely in love with it. Quote Link to comment Share on other sites More sharing options...
stevenong Posted March 3, 2007 Share Posted March 3, 2007 Hey Edward, Mario's shader doesn't work for me when I tried it. Does a motion blurred object show through for you with Mario's Glass shader? Thanks! Cheers! steven Quote Link to comment Share on other sites More sharing options...
edward Posted March 3, 2007 Share Posted March 3, 2007 Oops, no. I just wanted to plug Mario's shader. I assume there's a good technical reason why not? Quote Link to comment Share on other sites More sharing options...
Dennis Sedov Posted March 3, 2007 Share Posted March 3, 2007 Oops, no. I just wanted to plug Mario's shader. I assume there's a good technical reason why not? Another idea is to get a motion vectors for that part and just comp MB in post for the refractions Quote Link to comment Share on other sites More sharing options...
Jason Posted March 5, 2007 Share Posted March 5, 2007 I haven't tried it for cases like this, but you could try switching Mantra into full raytracing mode by supplying the "-r" switch to the mantra command on the rop. So in the ROPs Command field, put: mantra -r Quote Link to comment Share on other sites More sharing options...
stevenong Posted March 5, 2007 Share Posted March 5, 2007 I tried mantra -r & it didn't work too. I don't know if there's an option or something I forgot to specify. I used a VEX Super Material & it worked. Something is funky with the refractlight() or reflectlight() functions maybe? Cheers! steven Quote Link to comment Share on other sites More sharing options...
AndrewVK Posted March 5, 2007 Share Posted March 5, 2007 Something is funky with the refractlight() or reflectlight() functions maybe? reflectlight(....) works fine. Something wrong with refractlight(...) function (as well as raytrace(...)) Color channel renturns colors without MB.... while opacity channel returns mixed opacity (wihtout MB over motion bluried) Quote Link to comment Share on other sites More sharing options...
beeemtee Posted March 5, 2007 Author Share Posted March 5, 2007 thanks for the fast responses, unfortunately i wasn't able to check your ansvers yet, but as i do it now, i see that i have to dig a bit deeper to resolve this.. if i find a solution i gonna post it here. but anyway thanks again. cheers bmt Quote Link to comment Share on other sites More sharing options...
andrewc Posted March 6, 2007 Share Posted March 6, 2007 You might be able to work around this by extracting the two geometry (the refractive plane and the refracted objects) into seperate geometry nodes. Mantra in H8 has a shortcoming that requires raytrace motion blur to be disabled when the rays are traced against the same object. Andrew Quote Link to comment Share on other sites More sharing options...
stevenong Posted March 6, 2007 Share Posted March 6, 2007 Hi Andrew, The tests I did were with a box & not a plane which is why motion blur didn't work. I split out the box into six separate Geometry objects & it works now (File attached and using Mario's Glass shader Pt 4). I guess users have to be aware of the shortcoming & plan their render carefully if they want raytraced motion blur. Thanks for letting us know about this. Cheers! steven glass_mb.hip.gz Quote Link to comment Share on other sites More sharing options...
Mario Marengo Posted March 6, 2007 Share Posted March 6, 2007 I just saw this. (hey Ed, thanks for the plug! ) Yes, separate objects, like Andrew and Steven said. Here's a test with houdini's built-in shader: And here with the custom shader: And the hipfile (sorry for the redundancy Steven, I was in the middle of making the test when you posted... you beat me to it ) testMB1.hip Quote Link to comment Share on other sites More sharing options...
stevenong Posted March 6, 2007 Share Posted March 6, 2007 Hey Mario, I like your setup better though. Thanks for posting your file because I haven't had much chance to use your Glass shader & that looks like a good setup for lots of render tests! Cheers! steven PS I know you're busy but please try to finish up the glass shader eh? Quote Link to comment Share on other sites More sharing options...
stevenong Posted March 6, 2007 Share Posted March 6, 2007 After looking at Mario's file, I realised my folly in the file I posted. I literally split the box into 6 faces/planes & put them into 6 separate objects. I did that because I was using micropolygon rendering which didn't give me the result. I should have used raytrace (mantra -r) rendering to test. I don't know why my earlier tests didn't give me the result I got today. I'll put this down to user error but many thanks to Andrew for highlighting a small shortcoming of mantra (which is easy to deal with) and Mario for showing the right way! Cheers! steven Quote Link to comment Share on other sites More sharing options...
Mario Marengo Posted March 6, 2007 Share Posted March 6, 2007 PS I know you're busy but please try to finish up the glass shader eh? :whistling: Soon, I promise. Quote Link to comment Share on other sites More sharing options...
meerkat Posted March 18, 2007 Share Posted March 18, 2007 i have downloaded mario,s example file and the sphere still renders without motion blur when i rendered with raytracing: is there something extra that i was meant to do that i have missed? amir Quote Link to comment Share on other sites More sharing options...
Jason Posted March 18, 2007 Share Posted March 18, 2007 is there something extra that i was meant to do that i have missed? Hi there, Which build of 8.1 are you using? I just spotted a fix on the Journal: Thursday, Febuary 8, 2007Houdini 8.1.872: Fixed a bug where mantra would reset the time for secondary rays to 0 in raytracing only mode (mantra -r). This change should fix self-occlusion artifacts that appear in secondary lighting when rendering with motion blur in this mode. ...it speaks about self-occlusion artifacts, but having the correct time on seconday rays sounds like it should be very important for this too. Could you download a build post-8.1.872 and give it another bash? Cheers, Jason Quote Link to comment Share on other sites More sharing options...
meerkat Posted March 18, 2007 Share Posted March 18, 2007 Hi there,Which build of 8.1 are you using? I just spotted a fix on the Journal: ...it speaks about self-occlusion artifacts, but having the correct time on seconday rays sounds like it should be very important for this too. Could you download a build post-8.1.872 and give it another bash? Cheers, Jason could be i am using build 8.1.704 right now. i will have a check. thanks. Quote Link to comment Share on other sites More sharing options...
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