Chaos Corona Forum
Chaos Corona for Cinema 4D => [C4D] General Discussion => Topic started by: BigAl3D on 2018-05-18, 23:53:38
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This is the same scene from my shadow catcher post, but Now I have different questions so here's a new thread. As you can see in this image, I have added all the cars on the left. The background image is from Google Street View (Street View Download 360 app). Just find a location and it gives you an equirectangular image. Good resolution too, 11835 x 6656, RGB (8 Bit). One thing is the background/shadow catcher image is very soft compared to the actual image file I'm using. Why is this?
The Honda CR-V's passenger door (middle vehicle) is supposed to be white. After much trial and error, I cannot get that material to look white and reflective. It's based on the blue material, but white. In this image, I have applied a chrome material to the rest of the car, as well as, the sphere on the road. The chrome material's Reflection tab has 999 in the Fresnel IOR and 1 in the Glossiness. I figured this extreme would surely give me a mirror look. Nope. Why am I getting that look even with chrome? There are no Post settings turned on. I even cooled the Corona Sun down to 5500k.
Another issue is the extreme hotspots on the front of the cars. No amount of passes or denoising smoothes this areas out. How can I fix these areas? If need be, I can simplify this scene and upload it, but right now its too large to post.
Thanks for any tips.
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It looks like you used panoramic image from google maps for scene reflections. Certainly that image has low dynamic range (LDR), which is nowhere near enough for physically plausible scene representation. That's why your car looks grey instead of white and your chrome looks just plain wrong. For correct enviroment lighting and reflections you need high dynamic range (HDR) image, something that you can't get from google maps. You can use LDR image for shadowcatcher and for background, but you need to replace it with similarly looking HDR image for enviroment.
Regarding those hotspots, it is reflection of your sun object. There are several ways how to deal with it. you can make sun invisible in reflections or use highlight clamping, both methods are very effective, but fake, therefore i prefer realistic method - use bloom and glare filter to simulate how camera sensor or eye perceives extreme difference in object brightness.
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Thanks for that info @Romullus. That makes a lot of sense. When I replaced my lighting image with a true HDRI, it made a huge difference. I found this great site that has great educational info on HDRIs and gives away a TON of them. Some with backplates. When you click on one, he lists the number of "EV" in the image. The higher the number, the greater the dynamic range. Pretty awesome resource.
https://hdrihaven.com/hdris/category/?c=all&o=popular
One question though, if I use a true HDRI that gives great lighting (but doesn't look good as a texture map), but I don't have a matching backplate, how could I use the Shadow Catcher in that scenario? Would I just need to make a very large shadow catcher object to fill the screen?
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It doesn't matter if you have backplate or not, you can use shadowcatcher anyway. And it doesn't need to be assigned to very large plane object, the plane just needs to be big enough to catch all the shadows from a scene objects (cars in your case).
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I'm having trouble understanding the setup. Can you elaborate? All of the videos I've watched use the light material in the Shadow Catcher material set to Environment.
I just tried adding a second Sky object with the same texture map I used for the shadow catcher. I get shadows on the material, but it does not line up with the background image at all.
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Hm, it might be hard to explain, since i'm using 3ds max and you - C4D. Generally when i want to use shadowcatcher and i have only HDRI without backplate, i put that HDRI into enviroment and plug it into shadowcatcher, which is set to enviromental projection. If i have HDRI and backplate, then HDRI goes to enviroment and backplate goes to envirment overrides>direct override and also is plugged to shadowcatcher, which in this instance is set to screen projection mode. And that's it, no additional objects with light materials are needed.
Maybe someone who works with C4D could setup example scene for you to analyze. Anyone?
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Here's a basic SC scene using the environment slot. I'll do another with the use of a backplate shortly. (Do not park your car like this, I've seen it happen in real life O_o)
Scene file https://mega.nz/#!1SYjkDDQ!4HQ6AyKvbZShrk64hCcsyTd-S3nkHDLszCyCXTkdK8o (https://mega.nz/#!1SYjkDDQ!4HQ6AyKvbZShrk64hCcsyTd-S3nkHDLszCyCXTkdK8o)
(https://forum.corona-renderer.com/index.php?action=dlattach;topic=20399.0;attach=85585;image)
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Thank you so much for your scene example. OK so the videos I have watched showed dropping the Light Material with the HDRI into the Shadow Catcher Environment slot. In your example, you have placed the Sky Object itself. I didn't think that was even possible. Interesting. That certainly eliminates my shadow catcher plane from having a wonky texture projected onto it.
I would assume I can use C4D's Camera Calibration tag to try and match the HDRI or is it the backplate?
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Here's my first attempt with my knew knowledge. Came out very convincing I think.
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Not bad at all, next step is working on the car paint! ;) But looking good.
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Thanks. What recommendations do you have for the paint?
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I'd probably go with a layered material. You download my one from here: https://www.corona-materials.de/en/material-library/car-paint/british-racing-green/135
Just adjust it to your liking. ;)
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Ha. Already was going there. I used the layered one with the null controller from the link below. So much to learn. This looks so much better.
https://www.corona-materials.de/en/material-library/car-paint/advanced-car-paint-xpr/235
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Do you guys create the cars by yourselves?
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Do you guys create the cars by yourselves?
For this example no. I used one from Cinema's content browser.
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I can’t build models like that. Usually from hum3d.com, squir.com. Cheaper than Turbosqud.con
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The reason why I asked was that I don't do cars. Found it boring to create them and also in general.
However, recently, I decided to try new things when I'll pick up work again, even cars...well, not proportionally correct ones. I want to exaggerate some things.
I've read some things and there was one thing that gave me nightmares (https://www.ebalstudios.com/blog/modeling-cars-polygons#horror).
I was just wondering if I'd rather go down the hassle of doing everything with nurbs (the cv-coons mesh seems very handy) or just go full on poly and not give a flying fuck about the reflection anomalies.
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I hear you. I actually would love to build a nice car model, but the guys at Squir for example, who are experts in this area and make hundreds every year, put in 40 to 50 hours for a quality vehicle model. And they know what they're doing!
I can't make money with a deadline of 3 days to animate something. Just not practical in a normal pipeline when I'm doing all the After Effects work, mixing the audio, doing any animations. The $75 – $150 is well worth it for me.
By the way, that is a very interesting article on 3D modeling and reflections. Another reason to let an "expert" do it for me.
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So a follow-up question to this topic. I have some footage we shot on a city street. I think I can use an HDRI that is a similar environment to get some lighting and reflections. I do NOT have an HDRI of of the actual location. Question is, how can I use the Shadow catcher and NOT use the Sky object (since it's a different shot and doesn't match shot I want to comp into) in the Environment slot? Make sense?
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OK, so I think I figured it out. I set the Shadow Catcher to Backplate and applied my image/footage I want to add 3D to. I also have a horizontal plane for the shadows and a vertical one in the background. I dropped the Shadow Catcher material on both objects and that gives me the proper projection. I'll post some tests soon.