Use Skybox material as reflection source

Is it possible to use the Skybox material as the environment map for reflective materials? Ideally this would also work with the PBR pipeline. My understanding is that currently only a TextureCube resource can be used - and in the case of PBR, only the texture cube associated with the Zone is used.

My goals is just interact with the Skybox material (say, something like this):

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For instance, in the “ForwardDepth” render path, it looks like the viewport is being sampled for a pass called “Refract”. I don’t know what that does, but it seems close-ish to what I’m after…

    <rendertarget name="depth" sizedivisor="1 1" format="lineardepth" />
    <command type="clear" color="1 1 1 1" depth="1.0" stencil="0" output="depth" />
    <command type="scenepass" pass="depth" output="depth" />
    <command type="clear" color="fog" depth="1.0" stencil="0" />
    <command type="scenepass" pass="base" vertexlights="true" metadata="base" />
    <command type="forwardlights" pass="light" />
    <command type="scenepass" pass="postopaque" />
    <command type="scenepass" pass="refract">
        <texture unit="environment" name="viewport" />
    <command type="scenepass" pass="alpha" vertexlights="true" sort="backtofront" metadata="alpha" />
    <command type="scenepass" pass="postalpha" sort="backtofront" />

Kind of getting the idea now…

So, rather than using some kind of screen space hack, I wrote a reflection probe component. This ties in beautifully with the existing PBR pipeline. Check it out:


Nice! Is there any slowdown it is hard to say from the video?

Nice! Is there any slowdown it is hard to say from the video?

I haven’t run the profile on this, but qualitatively, no noticeable performance hit. I’m using 1024 px^2 for each cube face, which might not be optimal on all platforms/hardware configs.

Also, I haven’t totally figured out the question of when to update the reflection probe. If nothing is changing, then it is overkill to update every from or even on a fixed update loop. Also, you might just want to have this in the editor and bake the probe to a texture on disk…For now, I’ve just implemented an Update() function that I have tied in to my specific use case.

I was thinking of doing a PR for this - would it be useful to anyone else?

Very nice
For less-shiny (or smaller) objects you wouldn’t need as high a resolution since it gets blurred anyway, but this would still make the objects fit really nice into the environment.
And I guess it would need some interpolation to work well on moving objects?

Too much fun:


I’ve been pondering implementation of a reflection probe component for Urho3D (something like what you get builtin to Unity) So, I would love to see a PR for this, or at least a look at your code? I could help with testing and tweaks if you wanted to try and make a PR out of it.

Sure, here you go:


Excellent. Thank you.

Seems to be working well for me. Thank you again.


Sorry for bumping this conversation again a year later, but I was wondering if anyone had any ideas about fixing a reflection scaling issue when using this probe technique.

I’m using it to simulate mirrors in a scene, and while I can see that the technique can only ever be an approximation of a real reflection, I noticed that in Unity, the reflection probe has a option for “box projection” which seems to help a lot in making scale in reflections look more correct.

More info here:

So, I’m wondering about the feasibility of implementing something like this for Urho, but I’m feeling a bit out of my depth. Would this need some work at the shader level to implement?