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Render Background Blurred...

5 REPLIES 5
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Message 1 of 6
darawork
4244 Views, 5 Replies

Render Background Blurred...

Hi all,

Just a quick question, probably an easy answer;

I have included a screengrab of a montage I'm currently working on.
On the left is a section of the MentalRay Render window.
On the right is a section of the actual background image used, as displayed in Windows PhotoViewer.

Why would the background be so blurred in the Render Window?

I have the render output size the exact same size as the original background photo.
Depth of field is turned off btw.
Render frame is a still, not an animation so motion blur shouldn't happen either.

Is there any setting in MentalRay I am missing or perhaps a Viewport Configuration setting?

Thanks 🙂

Darawork
AutoDesk User
Windows 10/11, 3DS Max 2022/24, Revit 2022, AutoCad 2024, Dell Precision 5810/20, ASUS DIY, nVidia Quadro P5000/RTX 5000/GTX760

5 REPLIES 5
Message 2 of 6
darawork
in reply to: darawork

"Limitations

The mental ray renderer does not support certain rendering features, as described here.

When you use a bitmap as an environment (that is, as a background), the mental ray renderer samples and filters it. This can result in unwanted blurring. To prevent background blurring, render the scene against a solid-color background, and then composite the rendered scene with the background image."

From:

http://docs.autodesk.com/3DSMAX/15/ENU/3ds-Max-Help/index.html?url=files/GUID-0BDEA015-99E1-43DD-9CD...

Well... that's a nice 'Feature' 😞

Time to learn alpha blending I suppose. I've been putting it off WAY too long.

Darawork
AutoDesk User
Windows 10/11, 3DS Max 2022/24, Revit 2022, AutoCad 2024, Dell Precision 5810/20, ASUS DIY, nVidia Quadro P5000/RTX 5000/GTX760

Message 3 of 6
spacefrog_
in reply to: darawork

Whats you image's resolution ?

What's your Blur settings in the bitmap rollout ?
Should be Blur:0 / Blur Offset:0, otherwise you image will be preblurred before it even reaches the renderer

Whats your AA settings in mental ray ?
Turn that up if it's below 1, otherwise you'll always get a blurred BG image. It does not even use each pixel of the BG image, but samples far less pixels than originally exist...
The "blur" effect as described in the docs is far more subtle than in your render example

And be sure that you do not have the image proxy system enabled...

Josef Wienerroither
Software Developer & 3d Artist Hybrid
Message 4 of 6
darawork
in reply to: darawork

Thanks I'll check those setting now, I know I have bitmap proxy off... but I can't check the AA/Blur settings until the current render frame finishes. I'll let you know how I get on later.

Thanks again.

Oh yeah, here are the original background image properties:

3872 x 2592 (Original image AND Render output frame set to same size)
Horizontal/vertical resolution: 300dpi
Bit depth: 24bit
Colour representation: sRGB
Compression bits/pixel: 4

Darawork
AutoDesk User
Windows 10/11, 3DS Max 2022/24, Revit 2022, AutoCad 2024, Dell Precision 5810/20, ASUS DIY, nVidia Quadro P5000/RTX 5000/GTX760

Message 5 of 6
darawork
in reply to: darawork

Turns out it was the Bitmap Proxy, I must have left it on from a different scene. Doh.

Where do I find the MentalRay AntiAlaising settings anyway?

{edit} Found it, under the renderframe window "Image Precision (Antialaising)" Slider, is that the only place?

Darawork
AutoDesk User
Windows 10/11, 3DS Max 2022/24, Revit 2022, AutoCad 2024, Dell Precision 5810/20, ASUS DIY, nVidia Quadro P5000/RTX 5000/GTX760

Message 6 of 6
Anonymous
in reply to: spacefrog_

I am using Arnold for Maya and this advice triggered an idea as to why the HDRI came out blurry in my renders. In Maya, the shape node of the Skydome that I plugged the HDRI in, I found Arnold blurs the image by default with its "filter type" set to "smart_bicubic" instead of "closest". I am now using 3Ds Max as well, so hopefully this knowledge will help me in future renders. Thank you!
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