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problems with lights and Sun


gmarkov1

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Hi. I use Autocad 2013 and I have a problem. Could someone explain to me why when I turn on the Sun and Sky Background, the spotlights automatically turns off? This happens every time and the render is awful... Bright windows, no light in the room :( And the opposite: When I turn off the Sun and Sky Background everything is ok. But the windows are dark....

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I suspect you have dialed up the intensity on the spotlights far greater than you should have to compensate, so when you add sun lighting it's just too much. Also, be sure that default lighting is turned off.

 

Is this an exterior or interior render? If interior, depending on the circumstances you could use just sun lighting and get just as good results with very little or even zero additional interior lighting. It's all about adjusting the Render Exposure settings.

 

Can you post a screenshot at least, and if possible the file itself?

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1.jpegHi, stykface. This is very simple sample. I wish I set up all the settings before the real rendering. It doesn`t matter how many lights I was putting on. The result is always the same. Look at the picture. I am trying to put LED-lights on the ceiling. I had changed all the lights settings - US/Generic/International and ... nothing happened.

2.jpeg

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Also, a word of advice... people tend to place lights in order to "fill in" light where it seems needed. Since AutoCAD now uses photometric lighting, it's best to replicate real world artificial light sources. If you're building an interior scene, place lights as if you would in real life. One/two bulb fixture in the center of the room from the ceiling; one or two lamps, add Windows with exterior lighting (with proper Render Exposure settings) and set the sun properties to Sky and Illumination to on. Make sure Final Gather is turned ON for accurate ray traced results. Always use soft shadows. Global Illumination is a must for added realism. Read up on Inverse Square Law for lighting to start understanding how lighting works, and always use Inverse Square for your lights. Use *.ies files when you can for best and most accurate lumination and wattage of lights.

 

List goes on. Use lights as if you would in the real world. Don't just randomly place lights just to fill voids, and don't randomly adjust intensities without purpose. Soon as this is grasped, your renders will start looking very photorealistic. Take it to the next level with 3D Studio Max to get the full mental ray rendering options.

 

Hope this helps. 8)

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Thank you very much, stykface. I will see the thread. Thank you for your advises too. One more question. These photometric lights (from Tool palettes), are they determined by default by the watts? Or it is necessary to import additional .ies files?

Do you think that 3D max is better than Autocad 2013 rendering?

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Do you think that 3D max is better than Autocad 2013 rendering?

 

I don't know if I would say better, just easier. Both programs use the Mental Ray rendering engine, so the rendered output is basically the same. It's just easier to get from point A to point B in Studio Max. You have a lot more options and much better control over textures/materials, lighting and rendering in Studio Max.

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Cad64 is correct. It's the same rendering engine, only the version installed with AutoCAD is a stripped down version. Studio Max has all the available options (that I know of), and in most tutorials I've been seeing lately, the options actually give you much more control and possibilities, making the version in Studio Max the preferred choice for serious rendering artists (if only these two applications were the only choices).

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That's exactly what I figured was happening. Refer to this thread in how to accomplish the best results for Indoor and Outdoor lighting by adjusting the Render Exposure:

 

http://www.cadtutor.net/forum/showthread.php?56138-Render-Exposure-Settings&

 

This should help you out. 8)

 

It was very helpful. But...Look at this cloud on the ceiling. What is the reason for that? I did everything exactly as it was written... :o

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The "splotches" are the individual photons from the ray tracing. Turning up your Rays and Photons/Sample helps this.

 

Here's the best "quick render" tip...

 

  • In RPREF, start out with the preset "Presentation".
  • Set Shadows to Segmented, Shadow Map to ON, Multiplier to 2.
  • Ray Tracing, set all three inputs to 20.
  • Turn on Global Illumination, Photons/Sample set to 2000.
  • Set Final Gather Mode from Auto to ON, and rays to 10000.

 

That's usually my "quick settings". In fact, here's an old thread I started that kinda covers some of these features from way back in 2009:

http://www.cadtutor.net/forum/showthread.php?35688-3D-AutoCAD-Render-Tip-Quick-settings-with-great-results

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So, to explain what's happening, there's not enough rays and photon emission for the rendering engine to calculate the lighting correctly. The more rays and photons and sampling you allow the rendering engine to do, then more realistic it can calculate light. Remember, when we look around we are seeing how light bounces and/or absorbs from every single object. Lighting is the most critical part of rendering because it's the benchmark for your render to have great output. You can have everything else done right, but if you can't let the rendering engine have what it needs to calculate the lighting, then it can't make the great results you want.

 

There is a penalty in these render settings though. It takes much more time for your computer to process the data. Lower your res or sit back and relax for awhile. :)

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Thank you, both. :notworthy: StykFace, I made a try with your setting and the final result was far much better. I did my previous (with the splotches) try with these settings: http://www.cadtutor.net/forum/showthread.php?56138-Render-Exposure-Settings& Please, tell me are the "render exposure" settings right in that link?

I will be absolutely honest with you and I have to say I don`t understand all these "rays", "photons/sample", "rays tracing" ect. Cad 64 has posted some tutorial and I will read them all. I have used Cad for years but not for rendering. I prefer it because I gоt used to it. But there are no tutorials for rendering. My goal is doing good renders.

Could you give me an answer about photometric lights? Are they imported in Autocad or I have to do something additionally, with .ies files? I think they are more useful than point lights. Working with the lights, what is more important "intensity factor" or "resulting intensity"?

Thank you once again.

 

p.p. Could you give Low quality settings, because I don`t want to waste much time with Presentation quality? I am begginner, after all.:)

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I will be absolutely honest with you and I have to say I don`t understand all these "rays", "photons/sample", "rays tracing" ect. Cad 64 has posted some tutorial and I will read them all. I have used Cad for years but not for rendering. I prefer it because I gоt used to it. But there are no tutorials for rendering. My goal is doing good renders.
I don't know a lot about it either, and you're right there's not many tutorials for rendering in AutoCAD. There's a ton for many other applications but not really for us AutoCAD users. But, the basic principles are the same, especially from 3ds Max tutorials.

 

Could you give me an answer about photometric lights? Are they imported in Autocad or I have to do something additionally, with .ies files? I think they are more useful than point lights. Working with the lights, what is more important "intensity factor" or "resulting intensity"?

Thank you once again.

Even though I don't know much at all about lighting, I do know the basics. Where I work now, I sit next to two electrical engineers who also engineer lighting a lot, too (since we are an MEP & S firm for the building industry). They have given me a lot of the "basics" about photometry since they calculate lighting values a ton. I never realized the science and engineering behind it.

 

So, you could just fiddle around with the settings or you could actually get into the study of light. It's up to you, but to get you started in knowing the basics, try these links:

http://en.wikipedia.org/wiki/Photometry_(optics)

 

http://en.wikipedia.org/wiki/Inverse-square_law

 

These are some very important basics. If you searching lighting tutorials for 3ds Max, you'll learn a lot too. Just apply the same principles to AutoCAD, since lighting is a science, and not "application specific".

 

Could you give Low quality settings, because I don`t want to waste much time with Presentation quality? I am begginner, after all.:)
You can't. If you want the best results then you have to have the best settings. I usually render in a medium quality with FG on and GI on @ 320x240 resolution just to get a quick glimpse. Only tip I can give you, honestly.

 

Again, hope all this helps.

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Thank you again. It is really helpful. Could you tell me, what is the optimal PC configuration for medium quality interior rendering? I mean about laptop. Because, saying honestly I had PC problems with Presentation Quality render. It has never started, that`s why I switched on to Low Quality. My laptop is I-3 2367, Ram 8gb, and Nvidia Geforce 650 1GB.

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A Core i3?!? Oh noooo..... lol. Core i5 is bare minimum but if you want to be serious, then you need a 3rd gen Core i7 minimum, 16GB RAM minimum. Video is decent but really need a much faster card with more memory. Basically a $3,000 laptop.

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6.jpegHi again. I am using your settings and everything is OK (according to my level). About this picture: can you explain me about the shadows on the ceiling? How can I fix them?

Thank you in advance.

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