I remember this conversation…and sometime afterwards it only occured to me as it should more often of what Houdini can allow you to do…and that is, make your own tools so you get the behaviour you want.
If one doesn't like the exposure paramater, or any other one for that matter - simply ‘hide it’ and create one with the expressions that define it's behaviour in whatever way you want, and call that parameter whatever you want.
What is up with light "Exposure"?
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- BabaJ
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- SpOOkyPaul
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I wonder if we could use this knob to create an actual exposure control, by adding a parameter to the camera and then relatively connect it to all the lights. I could then have a per camera exposure. The question only remains how to easily switch from one camera's custom global exposure parameter to another.
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- jsmack
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You can do this by modifying mislighting.vfl.
Instead of creating a spare channel on the camera, add a user property to the camera or ROP.
Call it “exposure” to work with the code below.
Unfortunately, user properties don't seem to trigger ipr updates correctly, but this example works as tested.
edits to mislighting.vfl follow:
key:
+ for insert
!= for modified
Jeff or Mark, if I did something wrong, feel free to correct me.
Instead of creating a spare channel on the camera, add a user property to the camera or ROP.
Call it “exposure” to work with the code below.
Unfortunately, user properties don't seem to trigger ipr updates correctly, but this example works as tested.
edits to mislighting.vfl follow:
...
float hitTime = now;
+ float exposure;
+ float expscale = 1.0;
+ int found;
+ found = renderstate("object:exposure",exposure);
+ if ( found )
+ expscale = pow(2.0, exposure);
// Make sure these exports are write-only
...
hitTime = svec.x;
!= float pscale = expscale;
float lscale;
...
feval *= (spec_scale + diff_scale) / spec_scale;
!= clr = leval * feval * expscale;
clr *= pbr_clampCf(clr, colorlimit);
...
if (light_bounces & type)
{
+ leval *= expscale;
+ lscale *= expscale;
_pbr_direct_multisample(clr, comp,
...
+ for insert
!= for modified
Jeff or Mark, if I did something wrong, feel free to correct me.
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- lor
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anon_user_37409885
A lot of work these days does not use traditionally trained camera/lighting people. They will happily look at a monitor or grade and just make it work. Any digital artists unable to deal with an extra control called 'exposure' is not quite right for the industry these days.
Sounds light Ior is simply advocating his business model of traditional training... lol. Next he'l be deriding the Richter scale for not showing earthquakes in a linear form so people truely understand the power of nature.
Hey, thanks for the insult, but this totally misses the point. How about civil discourse and debate rather than cynical insults. Anyone properly trained in photography understands. Those whose only argument is personal attacks should probably step back.
Edited by lor - June 20, 2023 16:09:25
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- Jonathan de Blok
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I used it once or make a few camera-exposure independent lights, long story, but it made it really easy since it was just a matter of linking both exposures, would have taken more time/math to make that happen without that slider.
A more serious use is when using HDRI environment light s, using it to match it's exposure to what ever the camera is set for.
I too found it a bit strange at first but if you think of it as "exposure compensation" it makes sense. It's also a quick way to dail-in lights over a large range, then use the intensity slider for fine tuning.
And btw, if you really want to go mad.. in the good old days of MentalRay you could use a negative intensity on lights to darken areas of a scene
A more serious use is when using HDRI environment light s, using it to match it's exposure to what ever the camera is set for.
I too found it a bit strange at first but if you think of it as "exposure compensation" it makes sense. It's also a quick way to dail-in lights over a large range, then use the intensity slider for fine tuning.
And btw, if you really want to go mad.. in the good old days of MentalRay you could use a negative intensity on lights to darken areas of a scene
More code, less clicks.
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- Soothsayer
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- Heileif
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lor
Hello ladies & gents,
I don't disagree that exposure , Fstop, Tstop, shutterspeed/angle should be a part of our toolset. Absolutely they should. But they should do what they do in a camera not something vaguely similar that can be roughly explained through convoluted logic. This control is not analogous to F-stop or Tstop, which affect all lights. This is a per light intensity control.
We have two things on set related to light. Lights and a camera. Lights put out a certain quality/quantity of light. Cameras receive it. Light intensity controls the quality/quantity of light coming OUT of particular light source. (This is what the new houdini light "exposure" control does). Camera exposure affects the light coming IN to the camera. the new houdini light "exposure" control does not do this. It's pretty simple. The exposure control doesn't control exposure.
We need a physical camera with functional exposure control.
For an example of a great physical camera, have a look at VRay.
In Houdini, the shutter"time" and fstop controls have no effect on exposure. There is, effectively no exposure control in houdini, making light intensity values arbitrary. So I can see why people are asking for exposure control, but it would be nice if that was actual exposure control, not a secondary exponential light intensity control, per light.
@Andy58, thanks for that quote. It is my opinion that lighting people SHOULD have to use huge values like 10,000. In this way they can begin wrapping their heads around the real nature of light. That's what real light intensity actually is! It is essential we break away from the old thinking that lights need to be at or below 1.0 int. Artists who start to get a handle on how friggin bright lights actually are tend to do better work and use their tools better, IMO.
Nick
@lor, Regarding "It is my opinion that lighting people SHOULD have to use huge values like 10,000." Do you only use the linear intensity still, even when working with spotlights?
Spotlights is the reason I started to use exposure on the lights instead. Hated those crazy high intensity values.
Edited by Heileif - June 30, 2023 21:59:31
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