Jamesdowling

James Dowling blog

Atmos. Making of-Part 2

I have used Vray for most of my career and when I moved into Architectural Visualisation 3 years ago, it was definitely the dominant render engine. However, about half a year ago I started to hear a lot about Corona, so in my spare time I decided to try it and see how it compared to Vray. This project was just something I made up for these test purposes only and was not commercial in the slightest.

Lighting

To light this scene I started with a HDRI map. I used the free Peter Guthrie HDR that comes with Corona, specifically 1347 Sun Clouds that can be found in the Resources-Materials section on the Corona website. This was added into the scene environment tab in a Corona output material which allows you to make exposure/colour adjustments.

01_HDRI corona output enviroment tab.JPG

On a side note – if you accidentally press the reset setting tab (which I did) it will get rid of the Corona output material as well, so to make life easier I add a zero at the beginning of the name so that it will turn up at the top of the scene material list and save me from scrolling through every material I made trying to find it.

02_HDR naming.JPG

For the internal lighting I didn't use any IES lights simply because I don't think it added anything to the look I was going for.

03_light setup.JPG

In Corona 1.6 there's now a function in the Light mix that allows you to change all your lights in the scene after the render and then paste those settings back into the scene lights once you've made those adjustments using the >Scene button.

04_scene.JPG

The reason you use this scene button to copy the values back into the light settings is because the lightmix is basically faking increase/decrease in light intensity. It takes the existing information it gets from the render and ramps up the intensity as you would if you had the pass separately in Photoshop – which, as you probably know, can create banding, noise, inaccurate reflections etc. But if you transfer the settings once you're happy with them, back to the light settings in the scene and re-render, it will give you a much better, accurate and crisp render.

As you can see in the screen grab above, the lights have an extremely high intensity (I didn't actually notice this until I started writing this breakdown and taking screenshots), which is a result of transferring the lightmix settings onto the light settings.

E.g. my sphere lights were very small and I had to increase them a lot in the light mix until I was happy, copied the values back into my lights and continued without going into the light settings again, hence the very high values.

Finally, for the external outdoor light bulbs and oven lights I applied a Corona light material to the filament geometry with a basic falloff going from white to orange, giving the light a softer glow.

05_filament light.jpg

Below is a light breakdown for one of the images so you can see what each light is doing.

Materials

I won't go into much detail into the Materials for this project as they are quite basic, but I thought I would include a screenshot of the wood decking of the external shot. I used the Multitexture plug-in by CG Source which, if you have not used it before, I would highly recommend, as it allows you to randomise textures on elements of an object. That was then put into a composite with more dirt layers added on top, plus monochrome versions created for reflections and bump. I also tend to add a coronaAO map on a 20% multiply to most of my materials diffuse colour to help bring out small details of a model.

Depth Of Field

I love depth of field with Corona, it is very intuitive and being able to view it in the interactive render with very little refresh times is a real time saver when trying to work out the intensity you want.

There are a few ways to set it up but I just wanted explain how I'm currently doing it.

To start off I set up my camera and by default the focal point is the point of the camera target. As long as the target is in the correct place when I set it up my shots, this usually works fine and would just need a little bit of adjusting.

Below are some examples of different positions of the target:

Camera target near the light bulb in foreground, planting in background out of focus.

Camera target near the light bulb in foreground, planting in background out of focus.

Camera target near the planting, light bulb in foreground out of focus.

Camera target near the planting, light bulb in foreground out of focus.

You can also put in the distance manually to add DOF at a later stage if you have already locked down your camera angle, but didn't set up the target. An easy way to work it out is to use either the environment or the clipping range in the camera settings: enable either setting and move the planes that appear to the object you want to be in focus.

Then copy and paste the value into the corona DOF override.

14_enviroment range overide focus.JPG

Now that we have specified the focus we need to work out the intensity of the blur. You can achieve this by changing the F-stop setting in the Corona camera mod.

15_fstop 2.jpg
Lower values are blurrier.

Lower values are blurrier.

17_fstop 25.jpg
Higher values are less blurry

Higher values are less blurry

Finally we need to determine the shape of the bokeh. If you go to the Corona render settings you can adjust the number of blades in the camera settings. This is basically recreating the mechanical shutter found in camera lenses. Generally, the better the lens, the more blades you get, which results in circular Bokeh - cheaper lenses tend to have more angular bokeh patterns.

The below examples show how a higher number changes the effect. You can also change it to circular or custom map in the drop down menu. Just play around a little with this until you have your desired look.

3 Blades

3 Blades

20 Blades

20 Blades

Extra Tip!!

Glass:

I did a few test renders of a scene and for 600 passes at 2500 pixels they were taking about 20 hours. I was using a i7 4930k Processor, but with depth of field and lots of displacement these kind of render times were not a surprise to me. I then started to render one camera that was looking through the back sliding doors into the garden area. I left it rendering as I was away for 2 days but when I came back to it, Corona estimated another 255 hours remaining....not good. I spent ages trying to work out why it was taking so long until I realised it was a little box in my glass material that I had forgotten to tick. I thought I would bring this up in case it helps anyone else that is currently banging their head against a wall. Even though I have been using 3DS Max for many years, there's still times that I forget about the simple things....normally a little tick box...

23_glass thin setting.JPG

 

Post production

Corona has great post production tools with a big collection of LUT's built in. For these images I used Kim_Amland_Photographic_01. It is also nice to not have to worry about shutter speed and ISO in the camera settings to adjust the exposure, although the CoronaCameraMod does have these options if you want to use them. I found that leaving them on the default settings and using the simple exposure setting in the post processing tab to adjust it worked really well. Below are the tone mapping settings I used:

24_Tone mapping.JPG

I found I could get the images to a standard I was happy with by just using the built in tone mapping tools. I did use Photoshop to increase some reflections and translucency but in the end these where very minimal and didn't add a huge deal to the images.

Below is a render from the Corona frame buffer and then the final Photoshopped version.

27_photoshop layers.JPG
Atmos. Making of-Part 1

Welcome to my first Blog post!

Hopefully one of many that will give an insight into my job and passion - 3D!

To kick things off I thought I would go through a scene I have been working on to test out Corona for the first time.

 

LIGHTS

The light setup is fairly basic - I used a Corona bitmap with a HDRI and input that into the corona background slot in the render settings. I do feel V-Ray's HDRI setup is a bit more intuitive when working out the sun direction as you can lock it to a V-Ray dome light which has the sun position marked on it. In Corona you can rotate it using degrees as a unit in the bitmap settings and combined with the interactive rendering it's straight forward to get the sun in the correct position.

First I put 2 blue Corona plane lights behind the windows (set to invisible), reflection and refraction turned off. These are very subtle but push some cool tones into the scene.

Disk lights are placed in the 2 lamps (far left and right in the above frame) with the kelvin set to 5000 to create warmth.

The filaments in the light bulbs in the chandelier have a corona light material with an orange to white falloff. They are not really lighting the scene but create a more realistic light bulb. In addition I placed spherical lights around the bulbs with the kelvin set to 4500 (warm). These lights are invisible and have "affect reflections" turned off in the light settings so they do not appear in the glass.

Finally I added 2 Corona IES lights above the sofa to add some more directional light into the center of the scene.

QUICK TIP!

Note for old Max users:

3DS Max 2016 introduced a new physical camera which has a tilt shift option included in the parameters (V-Ray cameras also have this option). At the moment Corona uses the max/ V-Ray camera in which you add a Corona camera modifier, but for users of 3DS Max 2015 or below like me you have to add a camera correction modifier onto the camera to add the tilt shift function which is vital for Arch Viz to keep all your verticals straightand to avoid distortion. To add this, select your camera, right click and select it from the quad menu.

The way I light a scene has actually changed since using Corona. When using V-Ray I would set up my lights and adjusting the colour/luminescence with a lot of test renders. In Corona 1.6 they have added a function to the Lightmix that allows you to change all your lights in the scene after the render and then paste those settings back into the scene lights once you've made those adjustments (using the >scene button, screenshot below). My new workflow now is to set up the HDRI light and roughly place the other lights using interactive rendering (very fast in Corona). I then render a low resolution image, playing around with the lights in the Lightmix until I'm happy and paste them back into the scene and that is my lighting done. I'm not sure if this was the intended use but its works for me and saves me so much time compared to V-Ray.

 

Corona has great post production tools with a big collection of LUT's built in. For these images I used Kim_Amland_Photographic_01. It is also nice to not worry about shutter speed and ISO in the camera settings to adjust the exposure, although the CoronaCameraMod does have these options if you want to use them (i.e. if you have to do verified views and need to match the DSLR settings). I found that leaving them on the default settings and in the post processing use the simple exposure setting. F-stop and Sensor width are important for Depth Of Field and I will go into that in more detail in a future blog post.

 

 

This scene is not a client project and is something I have created in my spare time, most of the room and furniture has been modeled by me, with the exception of the side cabinet, plant and a few accessories.

https://dimensiva.com/

https://www.ronenbekerman.com/free-window-corner-scene-for-v-ray-corona-and-octane/

 

For me this was also a great project to use my art as textures in this 3D scene. The image behind the sofa is an oil painting I finished in January 2017 which is now hanging behind my sofa in my flat. The other image is a pencil sketch. I think this is a nice way to combine my two hobbies so watch out for more of my artwork popping up in my visualisations!

You can see the final results below!

Atmos.
Atmos.
Atmos.
Atmos.