topic Re: Light passing through solid objects in AutoCAD Forum

Light passing through solid objects

Anonymous — Thu, 26 Jan 2017 17:25:42 GMT

Hi, I'm having problems with light passing through solid objects. I have:

3.8 thick panel from hardwood material (bed frame)
A point light (500 lumen) close to a panel

The problem is that light seem to pass through as shown on the picture

What am I missing? (I'm using AutoCad 2017)

Re: Light passing through solid objects

Alfred.NESWADBA — Thu, 26 Jan 2017 17:26:39 GMT

Hi,

welcome @Anonymous.autodesk.com!

Please upload the drawing, there are too many settings that can make that shining-through happening or not.

- alfred -

Re: Light passing through solid objects

Anonymous — Thu, 26 Jan 2017 17:28:15 GMT

Sure, its in the attachment.

Thanks

Re: Light passing through solid objects

Alfred.NESWADBA — Thu, 26 Jan 2017 18:25:09 GMT

Hi,

The panel behind the matress is 1.9mm thin, is that steel? Otherwise it would not work in reality.

The distance between the lights to the back plank is 0.6mm, from what I know the distance is too small for lights today.

Then there is the limit for rendering calculations for performance reasons. So materials which should not be transparent should have a minimal thickness, otherwise the light shines through that. Imagine the light is calculated by ray length, the smaller the steps you have to calculate, the more time is needed. The larger the steps, the faster is the rendering ... but in case the steps are to big some geometry objects are not seen by the calculation.

BUT ... all what I have wrote in the last 2 sentences is close to bull-****, because the calculation with current render systems works very different, but it was more easy to make it understandable (hopefully).

At least: look to your units, they are set to Millimeter. measuring your bed it results in 200mm long ==> wrong, I guess you meant 200cm, so use command _UNITS, set the linear units to Zentimeter ... and now try the rendering again, surprise, surprise 😉

HTH, - alfred -

Re: Light passing through solid objects

Anonymous — Thu, 26 Jan 2017 18:48:56 GMT

Well thats embarrasing. I changed the unit and it worked. Thanks 🙂

One more question: Do you have any recomendation on how to emulate rgb led strip behind the diffuser?

Re: Light passing through solid objects

Alfred.NESWADBA — Thu, 26 Jan 2017 19:04:41 GMT

Hi,

>> Do you have any recomendation on how to emulate rgb led strip behind the diffuser?

It depends on how realistic you need it.

One options might be to use a basic material and activate "Self Illumination" (simple sample dwg attached).

- alfred -