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Messages - houska

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Bug Reporting Cinema 4D / Re: Geometry not flat
« on: 2019-10-07, 16:22:38 »
The issue is caused by displacement in your Corona materials

Bug Reporting Cinema 4D / Re: Multi Instance
« on: 2019-10-01, 08:26:54 »
Hi, we will start working on this missing feature soon. It's something that has been requested a multitude of times, along with render instance and motion blur issues. Because implementing this is a complex feat that needs a lot of designing and research, I can't promise any usable results in a few days. However, we'll keep you posted!

Hi and thanks for the reminder. We are of course aware of this problem and have a fix planned. Just be aware that it will have the same problems as the motion blur, because it has to be implemented using motion blur.

Edit: Of course, ultimately, we want to fix the motion blur problems. Just wanted to warn you that this will not be any sort of a silver bullet.

Bug Reporting Cinema 4D / Re: Object motion blur
« on: 2019-09-27, 09:49:19 »
Hi edub,

yes, we know about this problem and it's obvious to us that it's very annoying to the users. We plan to do something about it very soon. A simple example/test scene will always come in handy, thank you!

I need help / Re: Light conversion to watts questions
« on: 2019-09-26, 16:39:11 »
Yes, the other way around would be multiplication by PI.

Lumens are the same as Watts, basically, you just have to multiply by some conversion factor, which says how much energy is actually visible and how visible it is (e.g. we are more sensitive to green light). There's a special function for that and it depends on spectrum of the light, but Corona uses a standard factor of 683 (see here:

The rest is obvious, based on the quantities (steradians and meters squared), so the equations would be:

[W] = [Lumens] / 683
[W/sr] = [W] / PI
[W/(sr*m^2)] = [W/sr] / S

Where S is the surface area of the light, which of course will depend on the geometry of the light.

Lumens describe the light of the whole light source, Candelas describe light only in one direction, which makes sense only on average or if you know which direction you are talking about. Without going much into the detail, in our case, you can just use PI again:

[Lumens] = [Candelas] * PI

Edit: Lux is similar to Candela in that it describes all directions, but only in one point on the light source, so you don't use PI as the factor, but the surface area S:

[Lumens] = [Lux] * S

I need help / Re: Light conversion to watts questions
« on: 2019-09-26, 15:43:43 »
Well, I would say that your calculations are not entirely correct. Maybe let's start with what quantities you have and which ones do you want to get?

Edit: Ah, you mentioned that in your recap, right? You want to go from Radiosity (W/m^2) to Radiance (W/(sr*m^2)), right?

In that case:

To get W/m^2 to W/(sr*m^2), just take the first value and divide it by PI (3.1415...). Area of the light does not matter, because it is not taken into consideration with these quantities (both are "divided by the area" already).

I need help / Re: Light conversion to watts questions
« on: 2019-09-26, 14:37:36 »
W/m^2 and W/(sr*m^2) are two distinct quantities. The former (radiosity) defines the average amount of energy leaving the light in all directions per area. The latter (radiance) defines the average amount of energy leaving the light source per direction and area. They are usually convertible between each other by differentiation or integration (depending on the direction of conversion), but in case of simple emission patterns, the conversion usually entails multiplication or division by some fractions/multitudes of PI.

Admittedly the topic is confusing enough for me too, so I have to refresh my knowledge every time I need to do some calculations.

This Wikipedia article usually helps me:

Also, do note that the sun's intensity is relative to Earth's sun. So the value of 1 means "one sun"

Yes, it's as I suspected. Look at this - a polygon object with Corona Light material vs. Corona Light object. Both are animated and both should be blurred. But the Corona Light object does not blur for some reason.

Thus, before we fix the issue, I think that you could create a sphere and apply a light material to it and your issue should be solved!

So I removed the fog, changed the environment, made the headlight lights visible and removed most of the objects in the scene.

From the result it seems like the lights are animated incorrectly. And indeed, if you look at the version with disabled camera blur, the lights actually don't move at all! This seems like a bug to me and we'll investigate it some more.

Hi, I just realized - there's an issue with motion blur and render instances, which causes some objects to move to weird positions. Can you try disabling render instances and use normal instances everywhere? That might fix your issue.

The speckles are actually probably caused by the light being shifted far ahead of the car in the motion blur timeframe.

That's an interesting setup to say the least. Is the Front/Back approach needed at all? I'd expect that you should be able to achieve the same result with only the opaque black material invisible to camera. The environment should then be able to shine through. That said, it's hard to be able to give you more specific advise without seeing the scene. If you want, you can use the private uploader to upload the scene or a relevant part of it for us to check it out.

Hi Br0nto!

Is you blocker material visible to GI? It should be, because those speckles mean light that is being reflected from the fog into the headlights and that is GI.

Thanks, Fabio!

We will include this in the next daily build

Guys, this is a feature of the "prevent black appearance" option for the lights. The thing is that it doesn't work in reflections or refractions. So your directional light will look white when viewed directly, but it will stay black when viewed in a mirror. This is not easily solvable because it's an unrealistic hack and because it's not exactly clear, in which situations the light should return white and when it should be invisible. For now, you can use a rayswitch material to circumvent this limitation.

Edit: So without seeing the scene and having more info, I would say that this has nothing to do with instancing!

Hi, I can confirm the issue! I reproduced it by creating a C4D Sky object with a Corona Light material with HDRI. Then I added the sky to a separate LightMix pass, yet the light still appears under the "Rest" pass. We will investigate this.

Internal tracking ID: 398410537

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