background image renders very dark in reflections

[phildlight]

If it's absolutely necessary, I'll post an image, but hopefully my explanation is enough.

I used a sky image in the max environ slot. vray sky in render environ override and sky image in render reflection override.

When I have "affect background" checked, the sky renders very dark. Almost black. With it unchecked, it's perfect, but the glass reflect the dark background still.

????

[phildlight]

here's the image. Actually, I discovered that the architect actually wan'ts "black glass" so I've got to keep it but the reflection should still show up more. you can see what I'm talking about near the bottom glass. It reflects the ground plane white and the background sky black. ????

[Clifton Santiago]

Well, its hard to be sure without more info, but...

First check your glass material. I usually have reflection color at 250,250,250 with fresnel checked. Then I unlock the IOR and set it at about 2.2. This will make the glass more reflective like you often find in architectural exterior glazing.

Are you using VrayPhysicalCamera? And HDRI reflection environment? I have found the HDRI's need to be amplified to correspond with the camera exposure. You will need to crank up your VrayHDRI multiplier to possibly as high as 100.

[jacksc02]

does the glass have any thickness?

[RErender]

This will always happen if you are using color mapping or physcam exposure. Overide the reflections with the same map with the output cranked up or better yet map a dome with a vraylightmat with the bitmap in it, cranking up the light value until it is bright enough. Make sure to exclude the dome from lights, shadows, GI etc.

[studioDIM]

Try and separate the glasses, and make sure the material assigned to them is "solo" not within a multi-sub or any type of material nesting.
But if the image is an 8bit one (ie. tga/jpg) rerender is right...

Lele

[phildlight]

The glass settings were right. I've been using this glass for a long time and it looks great normally. This time, I just used an image in the render reflect override, not an HDRI. That must be the problem. I made an HDR out of the jpg and multiplied it 120 times to get get the reflections right. What's up with that? Is it a bug? It's got to be due to the physical camera/sun/sky thing right? It never happened with the old dummy max camera. Now that i've got it figured out though, it's no big deal. Thanks for the help!!!

[Clifton Santiago]

No its not a bug. Think about how bright the Vray sun is with a standard max camera. The sun multiplier needs to be reduced to around 0.01, or 1/100th of its correct brightness. And with the standard camera an HDRI with multiplier of 1 or 2 looks correct.

With the VrayPhysical camera , the sun brightness is left at 1.0 and the exposure settings are adjusted to get the correct brightness. This means that the sun with its physically correct brightness is 100x too bright for the standard camera. It stands to reason then that an HDRI that looks correct with a multiplier of 1 with a standard camera would need to have a multiplier of 100 to look correct with the Vray physical camera.

[phildlight]

actually, that didn't work. Now with the multiplied hdr image, the rest of the image is brighter and tinted. If I put the vray sky in the reflection override, it reflects exactly correct. It's only when I try to use an image or no override at all.

[Dynedain]

actually, that didn't work. Now with the multiplied hdr image, the rest of the image is brighter and tinted. If I put the vray sky in the reflection override, it reflects exactly correct. It's only when I try to use an image or no override at all.

That's because if it's just in the environment slot, it will generate light in the scene. If you only want it in refraction or reflection, and not affect the lighting, that's what the refraction/reflection override slots are for.

[phildlight]

let me see if I can simplify the problem.

If I use vray sky in the reflect/refract override, everything is fine. I get the reflection of the blueish sky gradient from vraysky in my glass. If I use no override, and use a color in max's environment slot, I get the reflection of the color in the max env slot. It's when I try to use any image in the environment or the reflect refract slot that the glass just renders black.

I tried setting the vray reflect/refract override to a very high multiplier, but it seems to have no effect.

I'm confused. Which happens easily, so go easy here.

[phildlight]

the plot thickens! It was the camera!????? I created a new camera, set it up identical to the other one and it worked? Why? Has anyone had a camera go corrupt? The funny thing is, now when I go back to the original camera and render, it's fine. I was banging my head off the wall with the reflect/refract overrides, env mat, camera settings etc. and it was a stinkin bug in the camera!!!!! ARGGGGGGGGGGGGGGG

I did have to make the image an hdri and crank it to 100, but the reflection part was a problem with the camera.

[phildlight]

I think it was a ram thing

[glorybound]

HDRI

I have never gotten HDRI to work. I bought several good libraries, but they go unused. My probem is when I use them the environment is so close it us useless as a background or relection. An example would be a nice HDRI of a field with trees in the distance and a nice blue sky. When I use it in my scene all I see is trees. I open the HDRI in HDR Shop and convert it from a Latitude/Longitude to a mirrored ball. In my material slot I make sure I chose Mirrored Ball. Am I doing some thing wrong?

[Clifton Santiago]

If the HDRI appears too close to the camera, try opening the HDRI as a Bitmap map, rather than as a VrayHDRI map. This way you will have tiling control and you can double the tiling in the horizontal direction so the HDRI reflection appears to be further away.