Is it possible to use 2 HDRI on the same scene?

yuyu.atem

Hi! I am using a HDRI in mode draw dome (so I am using it as a background), but there is a part of the scene where I would like to use another HDRI, in order to give the impression of another world that appears, a bit like a portal or something. I am also thinking about using this item https://www.renderosity.com/freestuff/items/96337/portal-prop-for-hdri-environments to create a portal effect.

However, I don't know if using 2 HDRI in this way would be possible, or even if it would be the best way to create what I want. Could you give me some advicce, please? Thank you in advance!

Richard Haseltine

Not directly, as far as I know, but if you aren't wanting them to light the whole scene you might be able to make it work by applying them to spheres and  masking one out to leave just the bit visible through the portal.

markusmatern

The linked Freebie works quite well. However I don't have a finished render with it. If you want to use two HDRIs at the same time you always need to put one onto a spherical object, like done in the portal prop freebie.

I usually put up a portal object with a parented camera, load this into two different scenes and combine the renders in post processing. Here are two examples:

yuyu.atem

Thank you very much!  I think I understand the idea, however, I have 2 questions about the Portal Prop for HDRI environments (https://www.renderosity.com/freestuff/items/96337/portal-prop-for-hdri-environments):

- I am using the Strange Set (so the circular shape portal), but I would like it to be inclined, like that:

To do that, I just dialed the rotation parameter settings. However, here, we can only see the sky; I would like to see the landscape.
So, in the surface settings of the "HDRI Here" part of the portal, I dialed the horizontal and vertical offsets, because it's the only way I found to move the HDRI image in the portal. (I am using the environnement 010 which comes with the portal product).
However, the image become hugely deformed, that is not at all what I wanted:

So, I'm quite surprise: isn't there any way to move the HDRI image in the portal without deforming it?

- @markusmatern Could you tell me how you did to create this smoke effect around the portal, please? I find only these settings among its materials, and none of them looks like smoke...

Thank you in advance for your help!

markusmatern

I'm pretty sure just changing the horizontal or vertical offset in the tiling is not enough. The UV map of the inner part of the portal sphere basically uses a distorted form of a Equirectangular projection.
For such a projection it is not sufficient to just change the offsets. You need something like the free software Hugin specifically to change the projection of the image map fitting the rotation values of the mapped HDRI.

To answer your question: There is no eassy way to change the rotation of the inside sphere except only using the horizontal offset, which rotates the sphere. However you would need tilting for your example, which does not work by modifying the vertical offset, because of the Equirectangulat projection of the HDRI.

The smoke effect is from a product no longer available at the DAZ store. It had various smoke rings in VDB format in it. Now there is MMX VDB Portals, but I don't own it.

The basic workflow I mentioned above however should wotk with this, too. I'll try to elaborate more later on....

yuyu.atem

Ah, ok, I see...

Finally, I "fixed" the problem by rendering only the Particle part of the portal in my scene, and the HDRI part in another scene. Then, I recombined the image in Gimp. For, what I needed, it was enough...

Thank you very much! 

markusmatern

In both my smoke examples I did something like this, instead of the red ring I used the no longer available VDB smoke portals.
The camera is parented to the portal object, here the red torus.I saved the portal prop with the parented camera as  a scene subset.

Now I set up two worlds, sphere world

and cube world, and rendered both.

For post processing I loaded both renders and by drawing a mask inside the portal you now can look either from cube world to sphere world,

or the other way round..


I hope this helps. 

yuyu.atem

Yeah, I used a mask inside the portal too. However, is there any reason for which you used a cube world rather than two sphere worlds?

markusmatern

Here is another example I tried with the original portal prop, this is without any post processing

 

yuyu.atem

Thank you very much! 

markusmatern

yuyu.atem said:

Yeah, I used a mask inside the portal too. However, is there any reason for which you used a cube world rather than two sphere worlds?

I just was referring to the image with the  blue spheres as Sphere World, and the image with the green cubes as Cube World. Both are illuminated by HDRI spheres in Equirectangular projection.

yuyu.atem

Thank you very much!