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VrayLight/MeshLight. Same dimensions, same power yet different results?

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  • VrayLight/MeshLight. Same dimensions, same power yet different results?

    In a bid to better understand interior lighting, I'm running some simple tests.

    Essentially, the goal is to better optimize our exterior night/dusk exterior views renders, as we tend to work on large master planning scheme views that contain tons of buildings and thousands of apartments. Given the time of day and mood required for such visuals we need to show that these buildings are occupied, so we must have lights in apartments turned on.

    I always like to stick to as real world setup as is possible in my work, so I would usually create instanced vray disc lights (to mimic ceiling spot lights) space them out in one apartment room, raise them to just below ceiling level, group them and then proceed to copy the grouped instanced vray lights around scheme. Now, this is already a tedious job, but it gets to a point when for some reason Max starts to become slow and unresponsive with the number of lights in the scene (I'm talking view port and general max lag, rather than anything to do with rendering at this point). For example clicking on a group of lights can result in a 3-4 minute UI response when the scene is heavy with vray lights.

    After a nightmare experience dealing a ridiculously large scene I gave up on that approach and I played around with the idea of using a mesh light instead. So, instead of creating a Vray disc light and instancing that around the scene in groups, I created a circle spline, converted it an editable poly, flipped the normal and copied the circle in element mode instead. So, we have the same layout of spotlights lights, just this one is an object of circle polygons acting as one light, rather multiple instanced vray disc lights. To my utter joy, this approach worked, copying the circle elements around the scheme was smooth and I experienced absolutely no lag whatsoever. Then the simple task of applying the vray mesh light to the one object!

    The problem with this approach is, you have to crank up the power of the mesh light to unreasonable levels, crazy levels. I'm assuming this is because the light is being spread across many polygons (larger surface area). As a result buckets are getting stuck during a render over the lit areas even if the areas are not too bright, thus my render times have gone through the roof.

    I guess the question is, what is the best approach to lighting many apartments up in large scenes. I've seen the use of light image planes on the interior walls of an apartment. This seems like a good idea, but the floor plans we work with are not always uniform and would mean creating many different image planes for every different apartment specification.

    I've attached two images, one with a vray disc light emitting 1350lm, the second a circle mesh light with the same diameter and power, yet they show different results (the dimmer is the mesh light) to add, copying the mesh light circle around in element mode reduces the amount of light cast from the mesh light even further (again referring to my point about surface areas above).

    Your thoughts and ideas would be greatly appreciated!
    Attached Files

  • #2
    I haven`t used it but doesn`t 2019 have OSL shaders that can do this for interiors ? Looked rather clever. In fact there`s a thread on the forum and and a link to an OSL later in the thread.
    https://forums.chaosgroup.com/forum/...mapping-shader
    I`m not sure if it helps in your case ?
    anthonyh

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    • #3
      Originally posted by DanSHP View Post

      I always like to stick to as real world setup as is possible in my work, so I would usually create instanced vray disc lights (to mimic ceiling spot lights) space them out in one apartment room, raise them to just below ceiling level, group them and then proceed to copy the grouped instanced vray lights around scheme. Now, this is already a tedious job, but it gets to a point when for some reason Max starts to become slow and unresponsive with the number of lights in the scene (I'm talking view port and general max lag, rather than anything to do with rendering at this point). For example clicking on a group of lights can result in a 3-4 minute UI response when the scene is heavy with vray lights.
      We had big performance problems with groups. We avoid them almost completely now.
      We use selection sets, Layers and hierarchy now. Mostly hierarchy there is a cool soulburnscript which creates a helper and links all selected objects to it.
      German guy, sorry for my English.

      Comment


      • #4
        Originally posted by anthonyh View Post
        I haven`t used it but doesn`t 2019 have OSL shaders that can do this for interiors ? Looked rather clever. In fact there`s a thread on the forum and and a link to an OSL later in the thread.
        https://forums.chaosgroup.com/forum/...mapping-shader
        I`m not sure if it helps in your case ?
        anthonyh
        Yeah I've tried it. It is very cool! It seems a little too rough around the edges for the quality I'm after though. Generally, we don't really see too much detail inside either, just the ceilings, mostly skyscrapers from ground level looking up. So it's nice to see those ceiling spot lights.

        Those interiors we do see, I can populate with a few blinds, plants sofas etc.

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        • #5
          Originally posted by Ihno View Post

          We had big performance problems with groups. We avoid them almost completely now.
          We use selection sets, Layers and hierarchy now. Mostly hierarchy there is a cool soulburnscript which creates a helper and links all selected objects to it.
          Yeah, i guess I could use selection sets, but I still think even then selection of just one light will bring max to its knees.

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          • #6
            ...for example, I just threw together this crude render. Typical tower block.

            Both images both have lights on in the apartments.

            Image 1 with, is a collection of instanced vray disc lights at 1350lm (avoided using groups). There are around 3500 lights just in this one tower. I understand this is a lot, but using vray lights produces a really nice glow to the apartments, and the spotlights add a nice bit of detail (without them it looks a little bland). Also this method renders much, much quicker than the mesh light method I've tried.

            Image 2 mesh light circular polygons, same dimensions and power, but the light isn't powerful enough (due to surface areas, they are just black spots). The thing is, if you increase the power of the mesh light to get a similar look or amount of light as in image 1, render times go through the roof. So it just isn't feasible.

            So, it boils down to this.

            Vray disc light method. Produces exactly the look I want, but 3500 instanced vray disc lights in just one tower, in scenes sometimes containing 6 or more towers and then other lower resi blocks to boot, max just wants to kill me. Max chugs and it's impossible to work with.

            Mesh light method. A lot easier to setup, no obvious slowdown in max performance, but in order to get any light emission similar to that of disc light approach, the mesh light must have crazy values. And with that crazy render times.

            There has to be a better way of doing this right?

            edit: I should add, the mesh lights are one object so polygons are just moved from floor to floor in element mode.
            Attached Files
            Last edited by DanSHP; 16-07-2018, 09:10 AM.

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