nmn Posted June 16, 2009 Share Posted June 16, 2009 (edited) Hi everyone in fact i'm kind of stuck here so i need your help is there any way i can get a global illumination pass (GI alone without the AO included) and an AO Pass (grayscale ! without the colors) , if i'm using the vex global illumination shader ? in fact i took a look into the code of the shader and seems the irradiance function calculates the whole thing in one shot (i mean the color bleeding + AO ...etc) anyway i can get the GI alone and the AO (grayscale) alone to get them in different passes while using this shader ? waiting for your answers Danke sehr .. Cheers edit: i did a test, i created a shader with the same code of the vex global illumination but instead of irradiance i used irraadiance - occlusion , it gave me something that looks as if it's the GI pass, but i'm not sure if it's correct ... Edited June 16, 2009 by nmn Quote Link to comment Share on other sites More sharing options...
rob Posted June 18, 2009 Share Posted June 18, 2009 Maybe something like this r rse_simpleOcclusion.hipFetching info... Quote Link to comment Share on other sites More sharing options...
nmn Posted June 18, 2009 Author Share Posted June 18, 2009 thanks rob for your answer , but ... Apparently my question wasn't clear ? the problem is not getting the AO pass ... the problem is doing a render WITHOUT AO while using the vex global illumination light => i need the AO to be a separate pass and the color WITHOUT AO to be a separate pass to be used in comp, and my problem now is that i don't know how to get that color with no AO pass ! in my scene the GI is done with a vex global illumination light, so i prefer not to replace it with other GI techniques, because then i will have to redo all the lighting and i don't have time at all ... all pipelines get their renders in passes so i assume that houdini should have something to do that, that i'm missing ... Please any help is very much appreciated waiting for your answers Thanks Quote Link to comment Share on other sites More sharing options...
rob Posted June 18, 2009 Share Posted June 18, 2009 If you want to render passes you need to add the export parameters from your shaders to the Mantra > properites > output > add extra image planes. That way you can render out all your passes for comp. The AO from the irradiance style occlusion will then be in the diffuse pass. Quote Link to comment Share on other sites More sharing options...
nmn Posted June 18, 2009 Author Share Posted June 18, 2009 once again thanks rob , i know that one also , but hmmm maybe i'm not expressing my need very well i'll try and reformulate it again, with a simple example a white plane a red sphere and a point light with ray traced shadows, then on top of all of that a light template with vex global illumination shader set to full irradiance ( so now the vex GI is causing color bleeding and AO into our scene) and our scene has direct and indirect illumination and AO so now how would you get a pass that contains the direct and indirect illumination but WITHOUT the AO (my problem is that the AO and indirect illumination come together ... so no one can exist without the other (when using a vex GI) ... so seems i'm missing something here ... ) Thanks for your help, very much appreciated Best Regards Quote Link to comment Share on other sites More sharing options...
DaJuice Posted June 19, 2009 Share Posted June 19, 2009 Hay nmn, If you set the "Background Color" to black on your vex_gilight shader, that will be the same as no AO. You will still get color bleeding and bounced light from other lights present in the scene. Quote Link to comment Share on other sites More sharing options...
rob Posted June 19, 2009 Share Posted June 19, 2009 (edited) Well there's something I never knew ... Edited June 19, 2009 by rob Quote Link to comment Share on other sites More sharing options...
nmn Posted June 19, 2009 Author Share Posted June 19, 2009 (edited) DaJuice said: Hay nmn,If you set the "Background Color" to black on your vex_gilight shader, that will be the same as no AO. You will still get color bleeding and bounced light from other lights present in the scene. Hey DaJuice and thanks for your intervention i did some fast tests and i couldn't confirm your method mainly because when we take down the env color to 0 it changes all the lighting in the scene , any example that can help me see that ? so ... it's kind of problematic, because it's not only the color bleeding we need, but the whole lighting of the scene in which this BG color is an important contributor ... so not solved yet i'm afraid, in fact i thought it should be easy to tell houdini give me only the GI light without AO ... because all the rendering pipelines usually take the AO as a separate pass so don't want it included in other passes. and another question comes to my mind here, if you use the irradiance or the AO nodes inside a surface shader how do you get them in the calculation you add the irradiance and you multiply the AO ? (i know we don't use them together in the same material usually because irradiance calculates the AO also ... my problem source ... ) Cheers Edited June 19, 2009 by nmn Quote Link to comment Share on other sites More sharing options...
rob Posted June 19, 2009 Share Posted June 19, 2009 Well you need to roll your own shader then ! r Quote Link to comment Share on other sites More sharing options...
DaJuice Posted June 19, 2009 Share Posted June 19, 2009 nmn said: it's kind of problematic, because it's not only the color bleeding we need, but the whole lighting of the scene in which this BG color is an important contributor ... That "Background Color" is your occlusion. The Global Tint is a master dial for muting/boosting/tinting the effect of the gi shader as a whole, wether it's doing AO, Full Irradiance, or path tracing. You achieved the look of your scene while working with occlusion, if you turn it off, of course it will look different. :] If you still want to output a seperate AO pass to work with in post (everything is a white material, shaded with occlusion), then you should still be able to set that up in your shaders or with takes, etc. Not sure of the best way, I haven't dealt with passes in a while tbh. A quick re-creation of the scene you described: Quote Link to comment Share on other sites More sharing options...
nmn Posted June 19, 2009 Author Share Posted June 19, 2009 (edited) Thanks DaJuice for your help let me think outloud : here what you are saying is that the left side image is one with AO and the right side one is one without it, BUT look at the difference between the two (like the black shadow for example) - if we assume the second one is the pass without AO and then we do a grayscale AO pass and we multiply it with it, well ... i don't think we will achieve the left side image ... because you're right the global tint tints the whole GI , but it acts as a multiplier ... so if you have a zone in your scene which is already very dark it won't light it, because its light strength will come mainly from the BG color (which contributes to the lighting and not only to the AO in my opinion) hope i was convincing , i'm not believing that Houdini doesn't have something out of the box for such a thing :|:| - in fact i'm still hoping there is ... but i didn't find it yet ... Regards Edited June 19, 2009 by nmn Quote Link to comment Share on other sites More sharing options...
stu Posted June 19, 2009 Share Posted June 19, 2009 Ambient Occlusion, without the occlusion, is just a simple ambient light, no? And if you want an image lookup to contribute the ambient color to the scene without occlusion, then you're basically just dealing with a simple environment reflection scenario. Quote Link to comment Share on other sites More sharing options...
nmn Posted June 19, 2009 Author Share Posted June 19, 2009 (edited) stu said: Ambient Occlusion, without the occlusion, is just a simple ambient light, no? the question is not about an ambient occlusion without occlusion ... that has no sense in itself the question is a full render without AO enabled, a similar thing in maya would be ... using different mia_materials all over your scene on your objects, with any lights in the scene and evrtg, BUT without enabling the AO that's all it is about :| is it that hard to do in houdini with the vex global illumination?! Edited June 19, 2009 by nmn Quote Link to comment Share on other sites More sharing options...
DaJuice Posted June 20, 2009 Share Posted June 20, 2009 nmn said: if we assume the second one is the pass without AO and then we do a grayscale AO pass and we multiply it with it, well ... i don't think we will achieve the left side image ... Conventional wisdom is to multiply the occlusion pass with your ambient color, and then to add it into the comp (rather than multiply). I tried it with this example and the results are identical to using occlusion (aka Background Color) with full irradiance in the vex_gilight. Quote Link to comment Share on other sites More sharing options...
nmn Posted June 20, 2009 Author Share Posted June 20, 2009 (edited) DaJuice said: Conventional wisdom is to multiply the occlusion pass with your ambient color, and then to add it into the comp (rather than multiply). I tried it with this example and the results are identical to using occlusion (aka Background Color) with full irradiance in the vex_gilight. Ahaaa Awesome we got it finally ! Thanks DaJuice you rock in fact i knew it has to be calculated like this ( when i said multiply i meant multiply with the ambient) but from the looks of it i didn't expect it will give the same result (excuse my beginner experience with compositing), because in my head it was like 'AO is to darken areas of the image' but i never thought of it this way as in your example where it got the shadows brighter ... great so now i know how to do that full irradiance no AO pass, and the AO pass , but how do i create the Ambient pass ? Cheers Edited June 20, 2009 by nmn Quote Link to comment Share on other sites More sharing options...
DaJuice Posted June 20, 2009 Share Posted June 20, 2009 No problem. nmn said: how do i create the Ambient pass ? I believe all the materials in the pallette already have exports set, (the green colored nodes in the vopnet) with the ambient color being named paintExport. If you check those out you will see how it's done. Then once you are exporting from your shader, you also have to tell mantra to make use of the extra image planes of course. Quote Link to comment Share on other sites More sharing options...
nmn Posted June 20, 2009 Author Share Posted June 20, 2009 DaJuice said: Then once you are exporting from your shader, you also have to tell mantra to make use of the extra image planes of course. Ye sure. Thanks for all the help! i really appreciate it, that thing was driving me crazy lol i'll do some thorough tests with that new infos and will get back to you if i have more questions Best Regards Quote Link to comment Share on other sites More sharing options...
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