Glow

[Guest rzito]

Hello all,

 

I have had a few attempts at creating the effect of light emitting from within a model, see the render attach it was LEDs. I find that a lot of the detail in the interior diffuser surface is lost. Any tips or comments on how to get realistic glows through semi opaque and clear materials would be great.

 

Regards Ralph

[IronKevin]

It might be just the sheer brightness of the LEDs is so high it's washing out the surface detail.

[Bryan Cargill]

Glow refers to the interaction of light with:

1. surrounding objects and 2. the atmosphere.

 

1. You can accurately represent the light being emitted with surrounding objects by using the emission setting under the smart paint properties. It controls the light emitting from a surface. When non-zero, area lights will be located in an approximation of the surface. The greater the emission value the greater the intensity of the light being emitted. The greater the samples value the closer the approximation of the surface. Note that this is a computationally expensive thing to do- and will slow down your renderings. Frequently, a simple point/spot/area light source is a sufficent approximation.

 

2. The realistic renderer does not accurately compute light-atmosphere interactions, so there is no accurate way to rendering a glowing object. However, the lights do have a 'glow' setting. It is a simple effect where a fake glow is drawn by adding the glow color to the rendered color. The effect drops off exponentially at distance. As the glow is added to the rendered color, it will wash things out-- especially if the glow is bright or white. You can think of the glow as basically a 2d effect with the exception that the glow will be blocked by objects in front of it-- without consideration of transparency.

 

This means the glow will be blocked by your transparent surfaces. To make it visible, you will have to move the glowing light source in front of the surface. Note that the light and its glow are somewhat independent-- you may for example turn the light intensity to zero but still have a glow. This lets you locate the glow without effecting your overall lighting.

 

 

 

 

 

[Bryan Cargill]

This image shows some of the limitations of glow, and what I mean about it being 2d. Notice that the glow does not appear in the refacted portion of the cylinders as viewewd through the transparent box. The glow is totally blocked by the transparent box. The glow does not appear in any reflection either. Finally, note the 'washing out' of the glow is very apparent becasue its intensity and size are both large.

 

This image shows a smaller, glow combined with a bright point light using linear attenuation. The other lights have been dimmed to accentuate the glow. Of course the transparent box still blocks the glow, but it looking a bit better.

 

Finally, here I've moved the glow closer to the camera by creating a second light. I turned off the glow for the original light in the box. I've made the second light (closer to the camera, in front of the box) have ONLY glow as to not effect the scene lighting.

 

 

 

[Guest rzito]

Thanks IK & Bryan,

 

I guess it all gets back to trial & error, I'm going to try turning off all the lights except the ones in the LEDs. I saw one rendering I think it was Eric's of a glass and the faceting was really clear I'd like to get similar results.

 

Regards Ralph

[Guest EricFoy]

One thing that totally frustrated me for a long time was not having figured out this TIP:

 

If you are rendering transparent objects, MAKE SURE you have set "Render Both Sides of Surfaces" under Part Properties | Rendering. If you don't do this, the refraction will be way off -it will refract the light on its way into the material, but not on its way back out, resulting in very non-realistic appearances.

 

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thank you. thank you very much