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Lets make Lightmass EPIC (and understandable)

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    Hi Raghu, thank you as well for putting all this together- I really appreciate all the great help and the other folks who contributed- very much appreciated
    environment artist | VR Dev
    serriffe.com

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      I like your visual notes Raghu! thumbs up!

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        Awesome thread! I appreciate a lot all the contribution people are making.

        @DanielW (or anybody with that knowledge from post #8), if you could explain the functioning of Lightmass using Feynman Technique, surely most people would understand and we would progress a lot on this thread. Feynman Technique, for those who don't know, is basically about simplifying a hard concept and making analogies as if you were explaining it to a 5 years old child.

        Example:
        For a 5 years old child, this would be very confusing:
        "Gravity is described by the general theory of relativity as a consequence of the curvature of spacetime caused by the uneven distribution of mass/energy; and resulting in time dilation, where time lapses more slowly in strong gravitation"
        But this would be easy:
        "Gravity is what attracts the planets to the Sun and us to the Earth"

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          Did you just explain the Feynman Technique using the Feynman Technique? :P

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            Great thread! It was about time we would demystify Lightmass
            Alex Leiva

            Architect/Visualiser, National VR lead
            C o x Architecture

            LinkedIn: https://www.linkedin.com/in/alex-leiva-88187840/

            COLORAMA - Cinematic color grading // The Vineyard Challenge Solo – Runner Up

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              Hi guys! Finally I got some time to finish this.

              https://ue4arch.com/ue4archs-unreal-...rkflow-part-1/

              Thanks
              http://www.ue4arch.com

              https://www.youtube.com/channel/UCjp...pois6WVG6hqXNQ
              Latest projects

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                You're a god! Thank you!

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                  @ Rafareis. You nicely consolidated the whole tread. Thanks. Its going to help the new comers a lot.
                  Last edited by 3darchstuffs; 11-10-2015, 01:09 PM.
                  CHECK OUT:- Visit https://3darchstuffs.com/ for Unreal arch-viz tutorials, Unreal Demo EXE and Unreal projects with source files.


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                    Hi

                    Its a very intersting thread. Thanks a lot to all contributors, especially the thread starter Raghu, and of course DanielW for all the insightful information. Its very nice to have first hand contribution from a developer.

                    From the tests I made, the parameters from Klepadło (thanx!), post #169, seems to give a very similar result on Raghu's test scene to what Koola (thanx too!) gets with his parameters, post #172, but about 3 times faster and with no modification of the baselightmass.ini

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                      I have created few visual notes of my general understanding about the working of values in BaseLightmass.ini, need your feedback about the same.
                      'Scale' always means multiplier. Most of the 'Scale' variables in BaseLightmass.ini are to implement the various quality levels (Medium, Production). So for example NumHemisphereSamples * NumHemisphereSamplesScale gives the number of requested rays in the final gather. IndirectLightingQuality further scales up this setting.

                      Your calculation of total samples using NumHemisphereSamples * NumHemisphereSamplesScale * IndirectLightingQuality is correct. IndirectLightingQuality does affect a few other things though that also increase the build time.

                      @Daneil - Kindly let us know if this is the perfect solution to remove light leaks (combination of "NumIrradianceCalculationPhotons" + "IndirectPhotonSearchDistance")?
                      Unfortunately I have not done enough investigation with the photons to understand exactly what is going on to answer a question like this. The phantom lights happen because not enough photons were gathered to estimate lighting. Increasing NumIrradianceCalculationPhotons and IndirectPhotonSearchDistance will both increase the number of photons gathered, which is the right direction. However there are several steps in there and I'm not sure which one is the problem (direct photons, indirect photons, irradiance photons).

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                        Rafareis, great guide.

                        We can always work with the following relationship: the lower your “Static Lighting Level Scale” is, you will have to increase the value of “NumHemisphereSamples” to get away any bugs, thus causing a considerable increase in render time.
                        This is a good guideline. Lower 'Static Lighting Level Scale' means less reliance on smoothing, therefore the noise will show through. You have to then increase IndirectLightingQuality (NumHemisphereSamples) to compensate.

                        I recommend using 1024 (or greater) for lightmaps in walls / floors / ceilings that will receive a lot of shadow details from other objects in the scene.
                        Lightmap resolution has the most predictable impact on the final image quality. It's a good practice to always start working on quality issues with a lower lightmap resolution, and only set the the high resolution (1024) once you are confident in your settings.

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                          Originally posted by DanielW View Post


                          Lightmap resolution has the most predictable impact on the final image quality. It's a good practice to always start working on quality issues with a lower lightmap resolution, and only set the the high resolution (1024) once you are confident in your settings.
                          This confuses me because when I increased lightmap rez a lot of problems disappeared.

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                            Originally posted by RI3DVIZ View Post
                            This confuses me because when I increased lightmap rez a lot of problems disappeared.
                            Maybe because its about a different kind of problem. Increasing lightmap resolution indeed solves problems 'when' the problem is related to insufficient size of the uvmap dedicated to the lightmap of the object concerned.

                            @DanielW : my previous post went through the moderation and appeared before yours with a delay. When you mention increasing IndirectLightingQuality, does it only affect NumHemisphereSamples or also the parameters related to PhotonScale (NumDirectPhotonsScale / NumIndirectPhotonsScale / NumIndirectIrradiancePhotonsScale : parameters modified by Koola in his latest lightmass settings.) ?

                            Maybe I made a mistake somewhere but I'm curious to know if the observation I made in my previous post is correct : Koola parameters (involving Lighmass modification) vs. Klepadło parameters (no Lightmass modification & being faster).
                            It would be nice to have your insight on this if possible

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                              Originally posted by RI3DVIZ View Post
                              This confuses me because when I increased lightmap rez a lot of problems disappeared.
                              Issues with lightmap resolution and issues with the photon bounces should be distinguishable. So he's saying to thoroughly test your lighting settings (with iteration and faster builds) before committing to resolutions that will inflate your times. Only bump resolution when you have to.
                              Theia Interactive makes immersive VR experiences in collaboration with the world’s leading companies and creatives, leveraging this bleeding edge technology to pioneer the next generation of entertainment, storytelling, and customer engagement.

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                                This confuses me because when I increased lightmap rez a lot of problems disappeared.
                                I'm talking about when your texels are already on the centimeter scale, in which case 2x higher or lower is not going to make a huge difference in quality, but it will make a huge difference in build time.

                                You can use Lightmap Density viewmode to visualize texel size.

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