TUTORIAL/DIAGRAM: How Portals work and how to use them

[herraasgeir]

How exactly do I change a material to a portal material?

Say I click the material with the material picker and I have the settings in front of me. I can choose from diffuse, glossy, material mix and specular. I can also change emission, opacity etc. Where do I choose portal?

[ycarry]

Right-Clic: Add/Material/Portal

[herraasgeir]

When I right click and choose add -> materials I can only choose from: diffuse, glossy, material macro, material mix and specular. I'm using version 1.0 beta 2.46b. Is portal not in this version?

[herraasgeir]

Right, I answered my own question. It's in the 2.48 TEST.
Good concept, I look forward to using this.

[andi]

p3taoctane wrote:

How does one increase the portals strength...

So far I never used portals and I did not test 2.48. Nevertheless I'm pretty sure, that it would not be useful to change the "strength" of a portal.
As I understand radiance explanation, portals are only guides for the render-kernel through the geometry of the scene.
So everything should work as in the same scene without any portal. The only difference should be, that you need less samples to get a noise-free picture.
If this is correct, than of course the inside becomes brighter when you increase the daylight power and there is no need for a portal strength. A portal should be pure geometry as I understand it.

[Jaberwocky]

I've not used them in Octane yet.But from the times I've used them in mental ray you need to think of Portals as Funnels.

Their only function is to Funnel light through them and therefore there is less wasted light around the outside of them.

So if you put portals to cover a window.They tell the render engine where to direct the rays of light that are being produced.

Therefore more of the light rays enter the scene through the portals and fewer rays are wasted around the outside of it.The scene therefore converges faster.

If you need more light you have to increase the power of the emitter producing the light.Not the portals,which as I said before only serve to funnel the light.

[andi]

In Radiance explanation he speaks only about a sky/daylight environment. Do portals also work with other environments? What if one has no daylight environment, but only a blackbody emitter outside the box/room?
Is there a possibility to use portals for a light source inside the box? I was thinking about creating a cube shaped portal around a blackbody emitter or a rectangular portal in front of a spotlight inside the box. This would be great for small light sources!

regards
andi

[Jaberwocky]

In Radiance explanation he speaks only about a sky/daylight environment. Do portals also work with other environments? What if one has no daylight environment, but only a blackbody emitter outside the box/room?
Is there a possibility to use portals for a light source inside the box? I was thinking about creating a cube shaped portal around a blackbody emitter or a rectangular portal in front of a spotlight inside the box. This would be great for small light sources!

regards
andi

I guess the only way is to experiment.See what happens.

[roeland]

In Radiance explanation he speaks only about a sky/daylight environment. Do portals also work with other environments? What if one has no daylight environment, but only a blackbody emitter outside the box/room?
Is there a possibility to use portals for a light source inside the box? I was thinking about creating a cube shaped portal around a blackbody emitter or a rectangular portal in front of a spotlight inside the box. This would be great for small light sources!

regards
andi

Hi,

Portals work with any environment illumination, but not with emitters.

--
Roeland

[AndreaMannori]

Hi Octaneer, I just did my first test of an interior scene, a very basic scene I know. I followed all the suggestions of the Boss. I'm very happy of this result so I want to share my setup, step by step, just to clear any doubt about occlusions between portals and windows.
So.. you can see the attached images... first of all you have to create the walls and then to select the polys that will be the portals (don't cancel or separate them from the walls). Apply 2 different materials, one for the walls and one for the portals (you have to modify this material, inside Octane, by changing diffuse to portal). Further more you can add the glass geometry by selecting the edge loops all around the portals and then you have to create a spline from the edge with the appropriate command. So you can use this spline to create the glass mesh and the frame sweep. Finally apply a new glass material. You will obtain an interference from windows and portals but this is ok... when importing into Octane you will see all black, so just change the glass material from diffuse to specular and change the index to 1.01, change transmission to white or light blue and add some reflection. That's all. I hope you will enjoy it... and sorry for my bad english.
Cheers!