Chaos Corona Forum
Chaos Corona for 3ds Max => [Max] I need help! => Topic started by: subpixelsk on 2016-03-20, 17:14:44
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Hi all
I am not sure there is a definite answer to this but nevertheless I will try to ask.
I aim for photoreal rendering and am currently wondering how to light an interior properly
Going for very simple setup and atmosphere with sun and sky, not fiddling with intensity whatsoever, just default settings, increased only size a bit.
My main concerns is tweaking in corona framebuffer - I read a lot about keeping it linear - HC 1 and contrast at 1 when exporting an image to 32bit exr and will be grateful for your advice - I own also vfb+ and am happy with this plugin however I still am not sure if I am using it properly.
So the questions are - should I tweak values in framebuffer when I am going for vfb+ postproduction right after rendering or should I keep them at defaults? Is there any correct approach to highlight compression and contrast in framebuffer or is it all just artistic way of choosing the right values ? I have observed many photos where colorpicking highlights in photoshop showed pure white values so I am looking for the right ballance between contrast and compression to keep images from washing out and on the other hand from being unrealistic in terms of contrast.
I am not sure if I expressed myselft correctly but hope so :)
Thanks for any tip
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should I tweak values in framebuffer when I am going for vfb+
You write this confusingly but I guess by framebuffer you mean 'Corona framebuffer'. Because VFB+ is also framebuffer, just native 3dsMax one.
It's one or the other. If you plan to use VFB+, you select native framebuffer, you keep all color correction in Corona in linear format (1.0 HL, 1.0 Contrast) and also keep default 6500K White balance. Exposure is arbitrary so it doesn't matter but it should always be set roughly correctly or slightly underexposed for correct MSI behavior.
Then you can use color correction in VFB+.
I read a lot about keeping it linear - HC 1 and contrast at 1 when exporting an image to 32bit exr
Only if you need linear output for compositing or exposure tweaking. You can export .exr with Highlight compression and contrast, it will just be clamped. So the choice is purely dependant on your post-production workflow.
Is there any correct approach to highlight compression and contrast in framebuffer or is it all just artistic way of choosing the right values ?
It's kind of both... The default highlight compression in Corona, which is Reinhard, is not that good looking without further post-production (local highlights recovery, saturation, contrast) , not sure why it's so universally popular.
The filmic in VFB+ does better job, specially in keeping nicely saturated highlights.
But outside of that, it's scene dependant creative choice. You keep it as low as possible to avoid burn-outs without sacrificing too much which would result in flat and dull look.
Now burnouts are my specialty, I can't even count how many people asked me over the years "Help, my interior is either dark, or blown out/burned around windows !!". Well.... you either light it in way you need as little tone-mapping as possible (if that means flashlights/softboxes like photographer would do), or you bring it down with tonemapping, in exchange for flat look. There is no "holy grail" solution to this problem, no secret settings to lighting and photorealism.
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Thank you Juraj it really is much clearer to me now :)
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Do you guys have some recommendation for online courses? I mean photography, rendering, anything that would shed more light and help me to improve in rendering and understanding how photography and light works (as I am not a photographer). Did anyone tried 5SRW? I know it is for VRay but principles should apply to Corona in the same way, as it is not about the engine, but more about the artist ..At least it is what I tend to think
Thanks
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There are no high-level rendering tutorials that everyone dreams about :- ) No such 'easy pill' would have helped anyway.
The top studios and artists just developed their skill over time. Perfect observational skills are crucial.
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Actually I do not dream about such tutorials, only something to help me understand how to balance lights, etc. I know all these things can be learned by observation, I only guess some easy-to-follow courses would do the same magic over shorter time. I am self taught from the beginning, only lately I feel I have reached my limits..And that´s a bit frustrating
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How do you guys do test renders when working with linear files? Do you just temporarily increase contrast and highlight compression in interactive rendering when doing tests and then when saving 32bit exr just set those values to defaults? Because with LWF things looks awful in framebuffer. Thanks for any advice
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Yes, exactly like that.
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Thank you Juraj and can you please tell me how does vfb+ handle linear exr files from your experience?
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Currently with some issues a bit.... waiting for next version.
Otherwise not much point in asking me, I rarely use linear output for post-production. I use VFB+ so I can do that part in framebuffer :- ). Otherwise, would would be the point of using it ?
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Actually I do not dream about such tutorials, only something to help me understand how to balance lights, etc. I know all these things can be learned by observation, I only guess some easy-to-follow courses would do the same magic over shorter time. I am self taught from the beginning, only lately I feel I have reached my limits..And that´s a bit frustrating
If you want to understand how to balance your lights I have created a tutorial for this, you can ignore the first section regarding Gamma - this was for a particular colour matching setup. Corona uses Gamma 2.2 anyway so its not applicable - the rest of the information regarding the camera, lights and typical setup should apply though.
http://jamesvella.blogspot.com.au/p/tutorial.html
edit; Skip to the lighting section - the rest is for Vray. The environment lighting is basic with Corona so you wont need to do the HDRI setup - just put it in your Environment > Background and it should display your ambient lighting correctly.
As for your camera, unless you are matching a photograph or doing a photo montage - just adjust the exposure until you are happy and then balance with burnout. You will see in my tutorial why this is not so important - in short the photographer usually provides the retoucher multiple exposures and then they are done in post normally anyway.
edit2; Alexyork & Juraj explain this perfectly in this thread actually, https://forum.corona-renderer.com/index.php/topic,11405.0.html
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Thank you guys. A lot of times when working with interactive and then switching to native 3ds max buffer to be able to edit things in vfb+, the whole vfb panel disappears and there is no way calling it back unless I restart 3ds max - is this a known bug?
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Not one I am aware, never happened. You mean the icon with actual VFB+ isn't there ? Because it can be switched on/off from NativeFramebuffer tab.
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Yes the small + button disappeared..
(http://s23.postimg.org/rofni6njf/Untitled_1.jpg)
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Looks like this is your issue:
http://www.monotoneminimal.com/archives/806
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Looks like this solved the issue. Thank you !
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How do you guys achieve blue sky color like this https://pixabay.com/sk/modrá-obloha-mraky-vonku-scénický-290314/ ? By connecting to cc node and increasing contrast and then compensating intensity ? Or is there any more physically correct way to do this ? Because by default sky looks a bit washed out
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Your link doesn't work, but rich blue Sky happens as a combination of:
1) Correct angle, mostly frontal lighting.
2) Exposure blending
3) (optional, but greatly helps) Polarization filter
4) Post-production (selective color/contrast).
Have you seen recent making of by Santi Sanchez on Ronen Bekerman ? Go have look :- )
You want this, right ?
(https://openhousebcn.files.wordpress.com/2014/02/openhouse-magazine-opposite-attraction-architecture-casa-em-s-francisco-da-serra-by-gsmm-photography-by-ultimasreportagens-fg-sg-fernando-guerra-5.jpg)
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I am looking for something like your example but a bit less strong like in this link https://pixabay.com/sk/modr%C3%A1-obloha-mraky-vonku-sc%C3%A9nick%C3%BD-290314/ . I went over that making of and it´s great . As for exposure blending - does it mean only the sky would be the element here that would be replaced by lower exposure image?
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You have to consider part of that darkening is actually lens vignetting. Hence why this is good to do in post-production and not merely by under-exposing background override alone.
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Thank you - you´ve once posted a pdf with some sun/sky examples and there were two ocean renders - one interior and one exterior - was the deep sky effect done purely in postproduction in that case ?
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I honestly don't remember, I'll look it up.