[aqualis]

I have created an emitter that's based on a tileable texture. The goal is to use this texture to create a LED facade.


The facade is comprised of 10 different surfaces, and each surface has its own specific emitter assigned. This is needed because each surface has its own texture coordinates in order to align the textures across the facade. Here's a view of the different surfaces (material channel render), each color group of LED's depicts a separate surface / emitter:


In order to have control over the light intensity of the LED's, I decided to work with an image emission texture, as this keeps the light intensity per area constant, as opposed to using the surface as an emitter (with the above texture as a mask to obtain the LED effect), whose intensity is dependent on the size of the surface it is applied too. All the surfaces are different in size in this case.

First question: Is it possible to somehow define the intensity of an emitting surface (without image emission texture) as a constant per area? I suppose not, but nevertheless it would be quite handy to be able to define the emitter's intensity as "luminance emittance" (lux or lm/sqm), especially in the Rhino plugin, where textures can also be metrically defined.

The texture is applied to both the opacity mask and the emitter:



When I render this, with intensity set to 50, I get:


Even though I have used the same texture for both the emitter and the mask, there is a grey aura surrounding each LED. What I would expect is that everything that is not white light, would be transparant.

When I render this, with intensity set to 100, I get:


Raising the intensity gets rid of some of the grey aura, but also the light's fall-off is more abrubt. Somehow I would like to achieve a soft fade-out of light surrounding the LED's core.
Is there a way to achieve this? (get rid of grey aura and maintain soft fade-out)

On top of this, I would like the LED's to be emitting light on both sides of the surface. As there doesn't seem to be a "two sided" button to achieve this, I copy and move the surface 2 mm above the original, and apply the emitter with the normals facing the other side.

As a result, the aura around the LED's is even more pronounced: (upper half is 2 surfaces, lower half is single surface).


Any way to solve this??

[JDHill]

First question: Is it possible to somehow define the intensity of an emitting surface (without image emission texture) as a constant per area? I suppose not, but nevertheless it would be quite handy to be able to define the emitter's intensity as "luminance emittance" (lux or lm/sqm), especially in the Rhino plugin, where textures can also be metrically defined.

Yes, if your emitter is of the Color and Luminance type, you can change Luminance to Power, rather than watts/efficacy; then, you can set power units to lux.

On top of this, I would like the LED's to be emitting light on both sides of the surface. As there doesn't seem to be a "two sided" button to achieve this, I copy and move the surface 2 mm above the original, and apply the emitter with the normals facing the other side.

This is correct, emitters in Maxwell emit only in the direction of the surface normal.

Even though I have used the same texture for both the emitter and the mask, there is a grey aura surrounding each LED. What I would expect is that everything that is not white light, would be transparant.

Jpegs are often problematic for masking purposes, due to compression artifacts, and indeed this one has problems, at least if you are using the actual image posted above. Zooming in, the gradients looks like it is a gif. If you look at the half-cluster of on the right, it has an area (rgb 17,17,17 dots) bulging out toward the center. Were you to use a smoother gradient and save using a better format than the one-channel 8bit b&w that the image currently is, it should take care of the problem.

[Fernando Tella]

Maybe it would be easier just to use the mask over a normal emitter. You could change color without having to make another image or in multilight.

[aqualis]

Thanks JDHill for your input.

With the knowledge that I can have a constant emittance per area, my approach will change and I will proceed as Fernando suggests. Also thanks for your input Fernando.

I hope this will solve the issue.

[aqualis]

I have rendered the same model with the emitter set to {color and luminance > power >lm/sqm"}

The effect is that the render takes 3.5 times as long to get the same SL (8) and about the same emittance. It seems that by using a normal emitter, the render time is much more negatively affected by raising the power, than by increasing the intensity of the "image emission texture".

So, for efficiency's sake it would be faster to go with the "image emisson texture" approach.

Also, even if I bump up the luminance to 20.000 lux, I still dont get enough brightness out of the LED's. The core of the LED, which in the mask is pure white, even comes out black in the render.

So also in this case I seem to have more control with the "image emission texture"

FYI, for the moment I have't dealt with the texture's quality yet.

Also, I think the advantage to be able to control the color with the normal emitter is not really relevant, as it only exists in Maxwell itself. When I open up the .mxi in Photoshop, I can still select the separate layers with the emitters and apply an adjustment layer with hue/saturation > colorize and control the colors there.

Anyone has experience with the issues above?

[JDHill]

I cannot really speak to the efficiency of image emission emitters vs. masked emitter ones, not having tested that. As far as needing to use such a high power value, how does the math work out? Let's say that a 5mm LED puts out 0.5 lm (got that from here, using 5K mcd @ 20° spread). In a square meter, we can fit 40K of these, so 20K lux does not seem out of line. And indeed, here is a test showing, on the left, a 20K lux emitter plane masked with your texture, sized such that each "dot" is approximately 5mm. On the right are a collection of simple mesh planes, with 0.5 lm emitter applied:

• 

I'm not sure how you're getting the black dot in the center of each cluster, I do not observe that here (the dots above are because these emitters are 25mm above a plane, facing it). So, the first things I'd check would be scene scale, and whether it is reasonable to see a bright emitter, given the exposure value of the scene.

[aqualis]

hello JDHill,

Just for my understanding, the black dots on the image on the left are like mine, resulting from the image emission emitter?
(just because you say you don't observe them>> does that apply only to the image on the right?).

[JDHill]

The black dots in the image above are there because we are looking at the back of the emitters -- they're facing away from us, shining at a plane, which is 25mm further away from the camera. There are no mxis involved above, on the left is a masked emitter, and on the right, 52 individual emitter planes. Please let me know if that helps to explain it better.