Portal effect with two different hdri's I'm fighting with my scene where I want to show some kind of portal. All scene has illuminated by hdri №1. The objects behind the 'glass' (object with 100% transparency) should be illuminated by hdri №2. I'm using light path node to separate two 'worlds'visually and it works (according the shadows), but object behind the glass (box) has very weak impact from his hdri. It looks like settings of transparent material somehow affected the image behind or maybe transparency of it is not 100% transparent.

I don't want use compositing for this effect because of realistic effect I'm trying to achieve, so it would be great if someone you guys could share some thoughts or links that might help







cegaton Thank you very much for your help, advice and links! Especially for pointing at sockets colors. Now I'm digging both articles.

I changed the node tree using color mix node and set the Light Path node to Transparent Depth (and glass material set to transparent BSDF), and, unfortunately nothing has changed. :,-( The objects behind the glass now still highlighted poorly in comparsion with hdri connected straight to the output node. It looks like hdri is loosing it's light intensity in this case
Use a light path node and color mix node.

On the so called "portal" object use a transparent shader.

Then on the world, set the two different HDRs and use the transparent depth to control the RGB mix of the environments. 

Don't use shader mix nodes to mix RGB color information. Pay attention to the color of the sockets! Green sockets should connect with green, yellow with yellow, gay with gray and so on.

Also: nodes that are not connected to the final output have no effect on the result.

Read:
What is the meaning of the color of the node sockets in the node editor?

and 

Cycles - (Shader) Nodes - inputs outputs - What are the exact data types?


How this all works is

Transparent rays will use one image, all other rays (like diffuse or glossy, etc) will use the other. The limit of this solution is that glass objects (or other transparent or semitransparent objects) will need to be composited.