Yellow Spots on rendering

[GIJOE17]

Hi everyone,

Could someone enlighten me with some ideas of how to get rid of these yellow spots (see attached image). I just bought this HDRI (http://www.aversis.be/hdri/hdri-360-015.htm) and before I used it everything was fine. Do you have to use a blurry HDR for the GI and the non-blurry for the BG? If so hdr did not come with a blurry HDR, so the second question is how do I create a blurry HDR from a non-blurry HDR? If of course this is needed.

[Svetlozar Draganov]

This is usually happens on some HDRI if you are placed them in Vray Environment GI Override.
And the effect is even more prominent if some kind of multiplier is applied to the HDRI as Render / Overall multiplier from VrayHDRI map.
Probably the best solution to this issue is to use VrayDomeLight - and to attach this HDRI to texture slot in the properties of the light.
VrayDomeLight is optimized to work with HDRI and it will produce much better results than using HDRI in Vray Environments, you also have much more control over the light parameters.

[andybot_cg]

The best way to get enough environmental lighting in sketchup is to use fernando's method:

I made a video long time ago showing my method to combine HDRI + sun. Here is the link
http://www.youtube.com/watch?v=pqMoh...3&feature=plcp

Best

Dome light - coming soon to a Vray for Sketchup near you! (AFAIK this is one of the promised features for the next release.)

[GIJOE17]

Thanks for the reply. Looking forward to the dome lights! are there any examples using domelights you could point me to? Also I think I figured out why the HDRI is creating the yellow dots as well, I opened it in an HDRI editor and may four or five of the images had artificial suns added to the sunlight area using photoshop or something and the artificial suns in a real photo were yellow dots, so I am assuming this is causing the multiple light spots.

[ValeroStudio]

Your GI HDRI needs to be different from your BG HDRI.
GI - should be lower resolution and blurred in Photoshop using Gausian blur
BG - Hi-res version used for reflections
You can use Fernando's trick to add your shadows back if you want them.
The concept is spoken about here http://www.hdrlabs.com/sibl/index.html
I would also recommend purchasing high quality HDRIs. Peter Guthrie's get a lot of praise and I use them sometimes.
http://3docean.net/user/paguthrie/portfolio

[GIJOE17]

Thanks Matthew for the reply, if I don't have photoshop is there any other way to blur the HDR image and lower the resolution?

[ValeroStudio]

Not sure. Photoshop is one of the only ones I know that will edit and save HDR format. Maybe Gimp? I really recommend that you invest in Photoshop though. It's almost an absolute must for post processing and editing textures and will take your images to the next level.

[andybot_cg]

...I really recommend that you invest in Photoshop though. It's almost an absolute must for post processing and editing textures and will take your images to the next level.

+1! There's a lot to love about Photoshop. Definitely a learning curve if you're starting from scratch, but makes things so much quicker that strictly relying on the render to come out exactly right.

[ValeroStudio]

Just in case I really need to drive home how much you NEED Photoshop, watch this tutorial and see just how much 'rendering' happens in post. http://www.pixelflakes.com/tutorial/ps-breakdown/