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What's special about an HDRI background?

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So, if using the 'panoramic image' type background, the image can be an HDRI, but it doesn't have to be, is that right?

 

If it is an HDRI, then how does it behave differently compared to a 'normal' panoramic image?

 

Is it that it responds better to me adjusting the exposure on a rendered image where it's in the background?

 

Part of the reason I ask is to understand the pros and cons of using an HDRI panoramic background vs a 'physical sky' background.

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So it doesnt have to be, BUT the lighting (The renderwokrs background controlling environment lighting, i mean) from a "fake" HDR background will not be accurate, it'll just be generic single color light from everywhere. I have also seen issues when going to other applications, since C4D and some other 3D apps wont really allow "fake" HDR files and will sometimes just render them as a solid green or yellow to denote the issue.

I often use Physical Sky coupled with a heliodon for the environment lighting and then just the regular "fake" jpeg HDR background for the visuals and reflections to avoid this entirely. 

 

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Ok, thanks. So the HDR bit is mainly to do with how it affects environment lighting, rather than how the image itself looks.

 

Does that mean that the only time it would make sense to use the 'panoramic image' type background for environment lighting would be when (a) you want environment lighting to come from something other than a standard sky and (b) when you have a proper, not 'fake' HDRI available?

 

Following on from that question would be, if I want my environment lighting to be based on sky/daylight, is there any situation where there'd be a reason to use one of the HDRI panoramic image backgrounds instead of a 'physical sky' background?

 

It's only 'physical sky' backgrounds that let you have 'physical sun effects' ie. the colour and intensity of the direct sunlight changes according to the heliodon settings - have I got that right?

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2 minutes ago, line-weight said:

So the HDR bit is mainly to do with how it affects environment lighting, rather than how the image itself looks.

this is how I understand it, yes. i am not an expert on the tech but this is what I have gathered from reading and my own experimentation.
 

3 minutes ago, line-weight said:

Does that mean that the only time it would make sense to use the 'panoramic image' type background for environment lighting would be when (a) you want environment lighting to come from something other than a standard sky and (b) when you have a proper, not 'fake' HDRI available?

This seems solid reasoning.

 

 

3 minutes ago, line-weight said:

It's only 'physical sky' backgrounds that let you have 'physical sun effects' ie. the colour and intensity of the direct sunlight changes according to the heliodon settings - have I got that right?

Correct, only when you use a Physical Sky background coupled with an Heliodon that has Physical Sky and Physical Sun enabled in its OIP. If you disable those two checkboxes it just functions as a directional light object would.

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You could use a HDRI background of say a sunset. Imagine a Pink/Red glow is only present in about a 6th of the actual HDRI image. The result is that the rendered model is softly "lit" with a heavy accent of Pink/Red from a definite source. The results can be very satisfying. You can of course rotate that Pink/red glow around the model using the Rotation option in the the Renderworks background resource. 
I'd be interested to understand how the Heliodon tool interacts with HDRI backgrounds too.

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2 minutes ago, markdd said:

You could use a HDRI background of say a sunset. Imagine a Pink/Red glow is only present in about a 6th of the actual HDRI image. The result is that the rendered model is softly "lit" with a heavy accent of Pink/Red from a definite source. The results can be very satisfying. You can of course rotate that Pink/red glow around the model using the Rotation option in the the Renderworks background resource. 
I'd be interested to understand how the Heliodon tool interacts with HDRI backgrounds too.

 

Ok, so the HDRI background gives you specific light colour/intensity according to direction and what's in the image.

 

That doesn't work if it's not a proper HDRI though?

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I’m not sure. I’ve only ever tried it with Vectorworks HDRI images. EXR images are the ones I’ve imported from elsewhere and they import well into the Backgrounds editor.

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From my testing, Heliodons don't really interact with image-based backgrounds at all, they will ADD their light to any light generated by a background, but not change the temperature of the environment light based on time or anything like that. It is also not explicitly stated anywhere that I've been able to find in documentation that Heliodons interact with anything other than Physical Skies, so I didn't track it down much further after that.


 

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Thanks for all the comments, they help clarify a few things for me.

 

Another question. In the GSG video on Renderworks backgrounds one example is given of a 'chroma key' background, a kind of green-screen that can be swapped out in photoshop. But that's not going to work for backgrounds seen through glass, right?

 

Is there any way of exporting a render that has transparency to it? So, for example, if a background is seen through glass that adds a bit of reflection or other detail on top of the 'background', that area will be partly transparent when I bring it into photoshop allowing me to place it on top of a background image?

 

This I imagine must also be an issue with anti-aliased edges, using the green-screen method.

 

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4 minutes ago, line-weight said:

But that's not going to work for backgrounds seen through glass, right?

 

Is there any way of exporting a render that has transparency to it? So, for example, if a background is seen through glass that adds a bit of reflection or other detail on top of the 'background', that area will be partly transparent when I bring it into photoshop allowing me to place it on top of a background image?


Right. Well, depending on what photo editor you're using it may work and it may not depending on the tolerance of the chroma key or smart selection. However yes, it would require more poking and prodding. 

This is SORT OF possible using geometry behind the glass with Shadow Catcher textures applied, but its very situational as to when it would work and when it wouldnt, it also necessitates special renders that are ONLY for this export purpose, so it may not be efficient in every workflow.

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5 minutes ago, line-weight said:

Is there any way of exporting a render that has transparency to it? So, for example, if a background is seen through glass that adds a bit of reflection or other detail on top of the 'background', that area will be partly transparent when I bring it into photoshop allowing me to place it on top of a background image?

 

A few versions ago they introduced the ability to export PNGs with transparency (via Export Image File). I've used this a bit and the anti-aliased edges seem to export pretty well and look nice. I haven't tried it with something transparent like a window though.

 

For this to work the render style has to have to no RW background for there to be any transparency. For example, even a white RW background would make the negative space solid white instead of transparent.

 

I feel like the chroma key background method would have been useful before this functionality was present? Otherwise I don't understand why you'd need to greenscreen something out as opposed to just having native transparency. But I might be misunderstanding.

 

Note you should probably be rendering with Sheet Layer viewports for this to work best, if you're not already.

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5 minutes ago, Jim Wilson said:


Right. Well, depending on what photo editor you're using it may work and it may not depending on the tolerance of the chroma key or smart selection. However yes, it would require more poking and prodding. 

This is SORT OF possible using geometry behind the glass with Shadow Catcher textures applied, but its very situational as to when it would work and when it wouldnt, it also necessitates special renders that are ONLY for this export purpose, so it may not be efficient in every workflow.

 

 

Sounds like I'm better bringing the backgrounds into VW, in that case.

 

It's a shame there's not more scope to edit the background images within VW, like adjusting size, offset, horizon level, white balance etc 'live' so that you don't have to jump back and forth between photo editor and VW.

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4 minutes ago, Andy Broomell said:

 

A few versions ago they introduced the ability to export PNGs with transparency (via Export Image File). I've used this a bit and the anti-aliased edges seem to export pretty well and look nice. I haven't tried it with something transparent like a window though.

 

For this to work the render style has to have to no RW background for there to be any transparency. For example, even a white RW background would make the negative space solid white instead of transparent.

 

I feel like the chroma key background method would have been useful before this functionality was present? Otherwise I don't understand why you'd need to greenscreen something out as opposed to just having native transparency. But I might be misunderstanding.

 

Note you should probably be rendering with Sheet Layer viewports for this to work best, if you're not already.

 

I do render with Sheet Layer viewports, yes. If I wanted to try the PNG with transparency export, then I'd have to do that from a rendered design layer view, would I?

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By the way, I've been trying some renders with a straightforward image background (and physical sky/heliodon for environment background) but have noticed I'm getting these white fringes, like a kind of antialiasing problem. Am I doing something wrong?

 

 

Screen Shot 2018-08-07 at 19.49.49.jpg

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If Anti Aliasing is low, OR if the render isn't yet completely done, that can happen. But if AA is medium or high and the render is complete those are supposed to vanish. I always see them during the render process however regardless of quality settings.

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7 minutes ago, line-weight said:

If I wanted to try the PNG with transparency export, then I'd have to do that from a rendered design layer view, would I?


Nope it can be done from sheet layer viewports as well, i just use marquee export snapped to or just within the viewport crop and then exporting to PNG with alpha channel respects the transparency as it should.

I think if you do Current View though itll give you solid fill for the sheet layer area around the vp however, so watch out for that.

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30 minutes ago, Jim Wilson said:

If Anti Aliasing is low, OR if the render isn't yet completely done, that can happen. But if AA is medium or high and the render is complete those are supposed to vanish. I always see them during the render process however regardless of quality settings.

 

The render's completely done and AA (in the renderworks style options?) is set to high.

 

I tried changing it to 'very high' but it's still appearing...any other suggestions?

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How far of a zoom factor is that screenshot? If its over 500% it may just need to be fixed with higher DPI, however if its really messy all over the place send me that file and i can take a look.

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25 minutes ago, Jim Wilson said:

Nope it can be done from sheet layer viewports as well, i just use marquee export snapped to or just within the viewport crop and then exporting to PNG with alpha channel respects the transparency as it should.

 

Exactly, Sheet Layer Viewports should work well.

 

I've developed a workflow where I set up my viewports to be exactly 16:9 aspect ratio (via a RW camera), then I make the viewports exactly 16" x 9" in size, and I make my Sheet Layer print settings have a 16" x 9" page. I place the viewport aligned exactly with the page. That way under Export Image File you can select "Each Page as a Separate Image" and get a precise export of that exact 16x9" viewport (or whatever size you've set up). I've found this to be the only way to get a reliable pixel count on export, as whenever I use the marquee method it always seems a few pixels off and is always a little different for whatever reason. I also make sure the DPI on export matches the Sheet Layer DPI I've rendered at.

 

Hoping to one day have a clear and easy way to export a viewport's render cache pixel-for-pixel with a simple right click of the viewport...

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Also, regarding transparency - even before exporting you should be able to tell where the transparency is by simply putting the viewport in front of something else, such as a rectangle with a solid fill. That way you can tell directly in VW what you have.

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I've been right-clicking on viewports, copying and in OSX Preview app running the "New from Clipboard" command for ages now and its definitely the quickest way... However, that workflow won't deal with the png Alpha export.

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13 minutes ago, Jim Wilson said:

How far of a zoom factor is that screenshot? If its over 500% it may just need to be fixed with higher DPI, however if its really messy all over the place send me that file and i can take a look.

 

The screenshot is over 500% but I'd say that the white fringing is still noticeable when I'm only 150% zoomed.

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