A bug with LightMix

[Motsar]

Hello everyone, I'd like to report a bug with LightMix that I recently noticed.

I'm working in 3DsmAx 2024 + Corona 12
I was working in a scene in which I needed to make several types of light sources for several angles.
For this purpose, I decided to animate the switching on and off of the light from two angles for the first two frames 0 and 1.

After the animation, I recreated the LightMix and everything worked, but as soon as I moved from one frame to another, i.e. changed the type of light, the light sources that participated in the animation did not work in the LightMix anymore until I recreated it again

[Avi]

Hi,

I am unable to repro this on my end. Maybe I missed any step.

Can you please start a ticket and share your scene along with the steps to reproduce the issue on my end?

https://support.chaos.com/hc/en-us/requests/new

[Motsar]

I describe it in more detail and consistently:

1) Create light, in my case I created 3 corona suns.
I used the first sun for one main angle
The second sun is the main light source for the second angle
The third sun works through the instances only on water and tiles under water
2) I run the animation auto-keys, where on frame 0 I have the second and third suns turned on, and on frame 1 only the light from the first sun is turned on
3) I create a LightMix, and in this case I can adjust the light, but as soon as I move to the next frame, for example, from frame 0 to frame 1, it stops working.
Or rather, the light sources that were part of the key animation do not work, the light that was on the environment works

Is this more clear to you?

[TomG]

Well, the main idea behind LightMix is you don't have to animate the lights being on and off - you render once, and then from that one render you can turn things on and off in LightMix to get multiple images, saving on having to render multiple frames. Can you give more details on why that approach would not work here - render once with all lights on, then using either the VFB or the CIE, turn the lights on and off as needed for the first image and save, turn the lights on and off for the second image, and save (and then save the CXR so you can edit the LightMix again later if you ever need a different combination of lights on and off, or different intensities). BTW with Corona 12 you could now save those different light set ups by having two LightMix render elements, and then just swap between them in the dropdown list in the VFB.

[maru]

I am not sure if I understand this report correctly, but if you mean that you cannot control the intensities and colors of lights which are turned off, then this is expected. LightMix can only be used on lights which originally have some intensity in the scene. If a light's intensity is 0 or it's turned off, then there is nothing to adjust in LightMix. Think of it as a layer in Photoshop. If a layer's opacity is 0, then you won't be able to control its brightness or color because no matter what you do, you end up with 0 opacity.

[Frood]

If a light's intensity is 0 or it's turned off, then

It is handled differently for the sun obviously. If setting on/off state, the light data of the sun goes to the "Rest" element if switching from a frame where the sun is turned off to a frame where the sun is on. Restarting IR on that frame fixes this as well as animating intensity instead of switching on/off state.

• Load attached scene, there is a light and a sun in red and same in blue. The blue ones are only active on frame 0, the red ones only on frame 1.
  
• Start (VFB) IR at frame 0. Switch to LightMix channel. It should be black because light mix is active and only the red lights are checked to be displayed in LightMix.
  
• Now move to frame 1. You see the red light but not the sun (you can find the sun data in "Rest" element instead)
  
• Restart IR at frame 1. Now the light data is correct.
  

And btw: automatic sun selection in a corona sky has an issue with such a setup:
Press "8" and activate the background map, then (try to) render ir at frame 1. Disabling automatic setup solves that one.


Good Luck

[maru]

Thanks Frood, I will look into this ASAP (probably next week).

[maru]

This is now logged. (Report ID=CMAX-1314)