Is there a way to create blurry reflections for an HDRI material?

[magneto]

Hi,

 

I am trying to create blurry reflections for my reflection pass. I want to add a parameter to control this (0-1). For reflections, I am sampling the image using I and reflect it using N, then pass this to Environment Map VOP with my HDRI map which is very sharp specifically for reflections.

 

In the actual tutorial, the author is blurring the HDRI image beforehand and creates 10 different variations where you could specify which one you want to use in the material. I don't like this idea, so I want to do it in the shader.

 

My idea is to sample a number of rays instead of my original reflection vector, that deviate from this based on my blurriness/sharpness parameter and then average the sum of all these samples.

 

But I don't know how many samples I should get and how should I deviate my random vectors from the reflection vector?

 

Is this a good idea? I quickly checked Mantra Surface parameters but I believe it doesn't offer control over the blurriness of the reflections using an HDRI reflection map? A pic that shows my idea, instead of the just green ray, firing the yellow rays:

 

 

 

Thanks for any advice

Edited March 7, 2014 by magneto

[Guest tar]

Specular Angle blurs reflections. MantraSurface/Surface/Reflect/Base/Reflect Lights

[magneto]

Thanks Marty, it seems like Specular Angle drives Physically Based Specular VOP inside which produces a normalized reflection BSDF. I never used BSDFs before but how can I use this to sample an HDRI map via Environment Map VOP which doesn't seem to accept BSDF values?

 

So for a value of 1 for sharpness, the surface will reflect the HDRI map fully in the reflection pass, which the map already is very sharp (different than the Diffuse Convoluted HDRI map), and a value of 0 will have very smooth blurry reflections. I assume the "stray" reflection rays will deviate as much as 90 degrees from the original vector.

[Guest tar]

 I never used BSDFs before but how can I use this to sample an HDRI map via Environment Map VOP which doesn't seem to accept BSDF values?

 

 

 

This, I leave to the experts!

 

I will take a look if I get some time

[magneto]

I can't believe I didn't see this. It's a lot simpler than I thought. There is a Filter Angle parameter in Environment Map VOP which does exactly what I want

[Guest tar]

happy to help

[magneto]

happy to help

 

Thanks Even the author didn't know this because he didn't use it, but instead created 10 different images that have different blurs. At least I know now, as promoting this parameter to the shader is a lot better than that pre-blurring images workflow.

[Annon]

Looks like this is new to 13... Nice one.