Altering the quality of light from an emission plane in cycles

Support Lighting and Rendering
1

Hi all,

I am currently creating a scene which has a number of fluorescent strip lights which should be visible objects within the scene, but also emit light onto the scene.

I have used a plane with its surface set to emission but when I render the image, the plane is too crisp i.e the edges of the light source are too sharp and therefore unrealistic.

I am wondering how I would go about changing it to look softer and more realistic?

Screen Shot 2015-06-09 at 11.00.56.png803×812 956 KB

Very much a work in progress but it should demonstrate what I mean.

Many thanks

2

I thought of a few options:

  1. Using texture on the emitter. ( Darker parts where you want to have less emission. )
    So it doesn’t look that sharp .
  2. Put the emission plane in a box with translucent material.
  3. I tried once with a blackbody node. As far as I remember that gave
  4. What about volumetric lights?

Just a few ideas to experiment with.

3

Thanks for the reply, this is my first Blender project so I have a few follow up questions and meandering thoughts on your suggestions.

With regards to the blackbody node, I have done a bit of research and that seems to be mainly for changing the colour temperature rather than the quality of the light?

I am interested in the volumetric lighting - if I understand correctly it basically adds a ‘fog’ across the whole scene which the lighting then interacts with? Will this work with an emissions plane, rather than a default lamp; i.e a spot lamp?

I am going to have a go at placing the emission plane inside a translucent material and report back.

I see that in compositing mode that a blur filter and glare filter can be applied - is there any way of adding these filters to specific objects i.e. the emissions plane, rather than the entire scene? When I add these filters it doesn’t seem to change the desired light in the OP.

4

Yes, you can isolate the emissive geometry in the ‘emission’ render pass, blur that in the compositor, and overlay it onto the image.

5

Nothing that a bit of tonemapping can’t fix.

Enable the curve correction in the color management panels, set the exposure to 0, set the max curve value to 2, and create a somewhat smooth curve where the visible part ends somewhere below 1 (this essentially will compress the highlights and reduce burnout).

6

Thanks for your reply.

I attempted what you suggested. Which was a great trick in terms of improving the overall look of the image (bringing back detail that was overexposed etc.) and certainly something I will use towards the end of the build.

But I am wondering whether you understood my issue, or more likely if I had explained it properly… at this stage all I am interested in is making the fluorescent strip light in the image look more flared/blurred - as at the moment the edges of the plane are too hard.

7

Thanks. Are you aware of any tutorials that would go into this technique in a bit more detail?

8

You could composite a bloom effect over the light to hide the sharp edges, or you could add a small volume around the lamp to get the same effect (with longer render times, but more realistic). If you want to go nuts with realism, you could also add a volume to the entire world.

9

Thanks. I am still unsure of how to composite certain aspects of the image (in this case the light) rather than the entire image.

Do I:

  • create a new ‘full copy’ scene
  • then delete everything from the copy scene except the emission plane of the light
  • then apply the filters to that copy scene
  • then mix the original scene and copy scene in the compositing node editor???
10

I’m rather new to compositing myself, but I think that you could use render layers here. Move the light to a separate render layer, then blur the light in the compositor and mix the two images. This is all just guesswork though since I’ve never used render layers myself, and I don’t know if it would work.

To get a simpler bloom effect, you can connect the image output to a color ramp node, set it so that only the very bright parts are white and the rest is black, then “screen” it over the original image.

11

Not sure if I already replied because my browser does weird stuff sometimes. Anyway,

you could duplicate the lamp and add it to a new render layer. Then, in the compositor, blur the lamp and mix it with the original image.

12

I appreciate the help so far guys. I feel that I am close to a breakthrough going down the compositing/layers route.

So I have moved the fluorescent light (emission plane) to the 2nd layer, with the 1st layer being the rest of the build. And I have managed to get both layers visible in the render.

However, I am trying to add the glare to the emissions plane layer but it doesn’t seem to be making any changes to the image.

I have attached a screenshot of the relevant screens, maybe somebody can see why it isn’t working?

Screen Shot 2015-06-17 at 11.49.21.jpg1913×978 511 KB

13

Ok so from doing a bit of digging online it appears that compositing does not appear in 3D rendered view, only in the render image/camera view?

14

Yes, compositing will only show up if you actually hit “render”. I don’t know if there’s a workaround for this, unfortunately.

15

Thanks for the confirmation. My end goal is to bake the the texture/shading onto the model for export to Unity, but haven’t yet looked into it. Now I am wondering if baking takes into account the “rendered” image or the 3-D rendered environment? I.e. if I clicked bake - would the compositing changes be baked on to the model or not?

If not, I may need to consider another method for altering this light.

16

No, I don’t think compositing is baked onto the models because it works on a 2D level. If you want to use this scene for a game, you might want to just add a plane to the lights and use a “fade-out glow” texture on that. Unity might also have some settings/effects to achieve a more realistic glow in real time.