Author Topic: Simulated "Tail Lamp" for car- not working?  (Read 1726 times)

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Offline Funktion_Dan

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Simulated "Tail Lamp" for car- not working?
« on: February 15, 2019, 05:27:22 pm »
Hello,

Looking for some help with lighting translucent materials.
I am attempting to "light" a tail lamp for a car. In the same way that the original car used light bulbs / reflector pockets with a clear lens-- I have replicated that scenario. The reflectors are a "chrome" material, the lens a translucent glass, and the bulbs are "Point Light Diffuse".

Even when cranked up to 2000 watts, the "Point Light Diffuse" material just doesn't illuminate the tail lamp. Actually I can hardly see it.

I know that light is traveling through the lens because I can see the reflectors- reflecting light back through the lens.

Have also tried "Emissive" materials, area light, etc-- pretty much everything I can see that is relevant.

What am I missing?
« Last Edit: February 15, 2019, 05:35:25 pm by Funktion_Dan »

Offline DMerz III

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Re: Simulated "Tail Lamp" for car- not working?
« Reply #1 on: February 15, 2019, 06:15:25 pm »
First few things I would check;

A.) How many ray bounces are you using?
B.) Do you have Global Illumination turned on?
C.) Scene units, are you using something that is applicable to 'real world values'? And if so, is your model to scale?


Offline Funktion_Dan

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Re: Simulated "Tail Lamp" for car- not working?
« Reply #2 on: February 15, 2019, 08:10:50 pm »
First few things I would check;

A.) How many ray bounces are you using?
B.) Do you have Global Illumination turned on?
C.) Scene units, are you using something that is applicable to 'real world values'? And if so, is your model to scale?

Hello!

Please see replies below:
1). Under the lighting tab- ray bounces is currently set to 50 ( see attached)
2). Yes
3). The scene units are in inches...the CAD model was generated in inches as 1:24 of full size ( I made the model for a production model kit which is 1/24 scale). The environment "ground size" is approximately 39" ( 1 meter). Other than that I don't know how to evaluate the units relative to everything else.

Note: you can notice that the bulbs in the Left hand tail lamp are assigned with the point light material- the ones in the Right hand tail lamp are not.

Thank you

Offline Funktion_Dan

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Re: Simulated "Tail Lamp" for car- not working?
« Reply #3 on: February 16, 2019, 11:52:22 am »
OK so I started over-- New Keyshot file. Sorry for all of the images but just trying to give you a complete picture.

Offline bdesign

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Re: Simulated "Tail Lamp" for car- not working?
« Reply #4 on: February 16, 2019, 02:57:06 pm »
Hi Dan-

A few things:

1. I assume the tail lamp cover is modeled to real world specs, as solid geometry with thickness (?). This is very important.
2. What material type are you using for the tail lamp cover? Enable Diffuse Transmission with a grayscale value approximately 15-30%.
2. The color of your point light is quite dark, and the radius value is quite high. Try color of 6500K to start, and tweak from there. The radius softens and diffuses the light; try reducing the value.
3. Try using lumen instead of watt.
5. Try enabling caustics.
6. You have global illumination bounces at 32- this is overkill and will greatly increase render time. 3-6 bounces should suffice.

Cheers,
Eric
« Last Edit: February 16, 2019, 03:05:42 pm by bdesign »

Offline DMerz III

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Re: Simulated "Tail Lamp" for car- not working?
« Reply #5 on: February 17, 2019, 08:25:43 am »
I second everything. BDesign has mentioned, especially the part about Watts vs Lumens. Often that is a tricky and misleading feature if you're scale and values are off in any way. Much easier to get a result using lumens.

Looks like the start of a beauitful image, hopefully this tail light gets sorted out and we can see your result soon!

Offline Funktion_Dan

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Re: Simulated "Tail Lamp" for car- not working?
« Reply #6 on: February 17, 2019, 11:10:20 am »
I second everything. BDesign has mentioned, especially the part about Watts vs Lumens. Often that is a tricky and misleading feature if you're scale and values are off in any way. Much easier to get a result using lumens.

Looks like the start of a beauitful image, hopefully this tail light gets sorted out and we can see your result soon!


Thank you both so much! I hope to have something to show within the next few days.

Offline DMerz III

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Re: Simulated "Tail Lamp" for car- not working?
« Reply #7 on: February 19, 2019, 08:06:56 am »
Also, just noticed you have caustics off, any changes when you turn that on?

Offline Funktion_Dan

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Re: Simulated "Tail Lamp" for car- not working?
« Reply #8 on: February 19, 2019, 04:58:46 pm »
Also, just noticed you have caustics off, any changes when you turn that on?

Hello! Yes I did turn caustics "on"

Offline Funktion_Dan

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Re: Simulated "Tail Lamp" for car- not working?
« Reply #9 on: February 19, 2019, 05:08:36 pm »
Hi Dan-

A few things:

1. I assume the tail lamp cover is modeled to real world specs, as solid geometry with thickness (?). This is very important.
2. What material type are you using for the tail lamp cover? Enable Diffuse Transmission with a grayscale value approximately 15-30%.
2. The color of your point light is quite dark, and the radius value is quite high. Try color of 6500K to start, and tweak from there. The radius softens and diffuses the light; try reducing the value.
3. Try using lumen instead of watt.
5. Try enabling caustics.
6. You have global illumination bounces at 32- this is overkill and will greatly increase render time. 3-6 bounces should suffice.

Cheers,
Eric

Hi Eric, yes the tail lamp lens ( and everything else in the car) has wall thickness was a contiguous solid entity before exporting. The "Lens" part even has a diffuser pattern modeled into the geometry of the inside surface.

Both Global Illumination and Caustics are enabled. Ray bounces is back down @ 5 for both.

I have been applying the recommendations here and getting some results! ( Attached are images)

The first material is an "Advanced" material with Diffuse Transmission set to a 20% grey. It glows when the lights are on. ( but it looks "milky" when the lights are "off" and seems to be refracting quite a bit of ambient light)

The second material is a "Solid Glass" material. It has a nice appearance when the lights are dark but it doesn't transmit light well.



« Last Edit: February 19, 2019, 05:15:42 pm by Funktion_Dan »

Offline MWo

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Re: Simulated "Tail Lamp" for car- not working?
« Reply #10 on: February 20, 2019, 12:36:25 pm »
Just look into the clear shiny plastics. There you‘ll find examples of advanced materials and notice that the color (red) is defined in the transmissions and not the diffuse channel. (Just like in the tortoise example: https://www.keyshot.com/forum/index.php?topic=23936.msg100439#msg100439)
A small transmission roughness should scatter the light.

Hope that helps


Cheers
Marco
« Last Edit: February 20, 2019, 12:40:06 pm by MWo »

Offline DetroitVinylRob

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Re: Simulated "Tail Lamp" for car- not working?
« Reply #11 on: April 25, 2019, 08:19:49 am »
Just a couple of thoughts on rendering automotive lighting...

Rear lenses of red and clear tail lamps are commonly PMMA plastic with a refractive index of about 1.58 and approximately 2.3mm thick. The reflectors are metalized plastic and generally look more like polished aluminium than true (exterior) chrome. If you did not optically design the CAD of the bulb (filament of bulb actually) to be relatively at the focal point of a true parabola (reflector), it will not collect and then collimate light along its vector (RV). This will also add realism with the uniformity of how it lights the cavity. Making the bulb clear glass will also heighten the level of detail in a specular aspect, and produce a more real looking product presentation.

To produce accurate and life-like renders we have done exhaustive research and I will share that using 64 samples at 33 ray bounces with self shadows on gives us our most realistic presentation.  You cannot merely accommodate for direct reflection and refraction, there are secondary and tertiary, etc bounces that add low level detail and hue changes. I'll see if I can show some examples...

Just my two cents as a lighting designer.

Rob

Offline DMerz III

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Re: Simulated "Tail Lamp" for car- not working?
« Reply #12 on: April 26, 2019, 11:05:41 am »
 :o Hey Rob, thanks for sharing your knowledge!

Would love to see your samples, I love it when people in the know get on here and help the rest of us newbies out!