dappled light issue using blend material and opacity maps

[matthew999]

Hello All,

I have come accross a strange issue. I was trying to create dappled light that imitates the effect of the sun behind a cutout metal sheet. so i created a mask applied it the cutout opacity. I dont want this geom the appear in reflections or refractions as that comes from a HDRI, What is wierd is that the effect doesnt appear on a blend material but appears on a standard vray material when im using an area light as my main source. However if i use a standard vray sun it works on both the blend material and standard vray materal

on the below images the forground sphere is a simple vray materal with coat enabled, and the back sphere is a blend material with stochastic and a coat

With vray sun dapple appears on both spheres



with area light dapple disappears on the blend material



Is this to be exspected or a bug?

Scene attached

thanks

matt

[matthew999]

what is wierd when rendering with an area light, if I re enable visible in reflections and refractions on the pierced plane casting the shadows then the dapple appears on the back sphere again, however i dont want the object visible in refractions or reflections,

[hermit.crab]

It's due to the light's Specular contribution, which does not consider an opacity mapped plane hidden from reflections/refractions. It is intentional since it caused other issues. I guess a workaround is to cut out the actual geometry, rather than using an opacity map.

[matthew999]

Hi Hermit Crab,

Thanks for your input, im a little bit confused sorry if this is a dumb question.... If its the specular contribution of the area light why does the dappled light appear on the standard material and not the blend material? Also when i enable render elements its got nothing to do with the specular contribution to the image, the effect appears on the lighting element.

thanks

Matt

[hermit.crab]

Hi Hermit Crab,
If its the specular contribution of the area light why does the dappled light appear on the standard material and not the blend material?

Both underlying shaders in the VRayBlendMtl are fully reflective (VRayStochasticFlakesMtl works by scattering thousands of mirror-like flakes), hence the lack of lighting information.

Also when i enable render elements its got nothing to do with the specular contribution to the image, the effect appears on the lighting element.

If you check the VRaySun's Specular contribution you'll notice it's on both spheres (unlike the VRayLight), whereas the lighting element is similar to the VRayLight version.