Render results different when I make the light invisible

[ferhankhan]

Hello, this is my first post on this site and I hope someone here might be able to point me in the right direction. Basically when I try to save out the render image with a transparent background as a PNG so I could edit the image with a city reference image behind the window 3ds max doesn't allow me to do that. I made the light in the scene invisible and tried rendering it that way and it worked, i was able to render it out with a transparent background but because I made the light invisible the render looks different to the original render.

 

This is the result that i would like for my render but the window is not transparent, light is not invisible

 

 

Here is the second render with the light set to invisible, the window becomes transparent but the look of the render is different

 

 

Any suggestions?

 

Thank you

[Devin Johnston]

Are you sure your not making the glass in the window invisible?

[Chris MacDonald]

Are you lighting the scene with a plane light at the window, or a VRay Sun/sky? Or both?

 

If both, the plane light is acting as a plane and blocking the sun, and thus casting a shadow - so when you make it invisible, you get both light sources.

 

If not, then you'll have to elaborate a little on how you have your lighting set up.

[Chris MacDonald]

I managed to replicate the issue based on the above:

 

[ferhankhan]

Hi guys and thank you for replying, I'm currently lighting the scene with both a Vray light and Vray sun. I think it might have to do with what you stated about the plane light acting as a plane and blocking the sun and thus casting a shadow. I'll have a print screen below of my lighting set up.

 

 

Is there anyway to render out the scene with a transparent background without making the light invisible.

 

Thank you

[ferhankhan]

Okay so I managed to fix the problem I was having by remving the Vray sun from the scene and having the only light source being the Vray light. Thank you guys for commenting in this thread and guiding me in the right direction, just something i wanted to ask there is actually no point of having both vray sun and vray light in the same location as i did is there or is that the preferred method for lighting up an interior scene.

 

Thank you again

[notamondayfan]

What you need to understand is that when "invisible" is unticked, the light shape will cast shadows. When invisible is ticked the light is hidden from casting shadows and affecting alpha channels.

 

When positioning vray plane lights in windows, always have invisible ticked if you have another light source behind it.

 

Dean

[Chris MacDonald]

It's your scene to light how you want, but I don't understand why you'd need both a plane light AND a vray sun setup. I could understand if you were using the plane light as a sky portal to force Vray to trace more samples in the room.

 

Do you really need both?

[notamondayfan]

I personally find using plane lights and a sun light, give a lot softer lighting, which I sometimes really like. The plane light would be quite low in power compared to the main light, but it still gives really nice soft lighting into the scene, and also spec / reflections too. Some people would use HDRs or images mapped onto cylinders / domes / planes for a similar effect.

 

Dean

[Chris MacDonald]

I've personally never had to use a plane light (other than as a sky portal) at windows. Usually a dome light, or HDRI, or VRay Sun do the job just fine.

[notamondayfan]

I guess they do the same trick, just add a little more light when needed. Another reason I prefer plane lights over dome / HDRI is I can manually tweak the intensity of each plane if needed to balance the image, where as a dome light is very universal.

 

To be honest, as long as the work looks good, does anyone care?!

[ferhankhan]

What you need to understand is that when "invisible" is unticked, the light shape will cast shadows. When invisible is ticked the light is hidden from casting shadows and affecting alpha channels.

 

When positioning vray plane lights in windows, always have invisible ticked if you have another light source behind it.

 

Dean

 

Thank you for explaining this for me, it's probably something I should have known but I couldn't figure it out for the life of me.

[ferhankhan]

It's your scene to light how you want, but I don't understand why you'd need both a plane light AND a vray sun setup. I could understand if you were using the plane light as a sky portal to force Vray to trace more samples in the room.

 

Do you really need both?

 

I was always shown that having both a vray sun and vray light set up would enhance the image but that was something we was taught by our instructor. The scene that I am currently working on at the moment will on just have the Vray light as it gives it a more warmer feel.