Increase Brightness of HDRI?

[kwhitt]

Is there a way to increase the brightness of an HDRI used as a backdrop?  Thanks, Kevin

[basketballman]

can you apply an emissiveness to its properties ?

 

in TM you just increase its brightness with a slider 

[Renerabbitt]

1 hour ago, kwhitt said:

Is there a way to increase the brightness of an HDRI used as a backdrop?  Thanks, Kevin

Backdrop Intensity is the only thing that effects your backdrop, though with automatic exposure, your sun settings effect(percieved) it as well

[Chief_Trent]

2 hours ago, kwhitt said:

Is there a way to increase the brightness of an HDRI used as a backdrop?  Thanks, Kevin

Hi Kevin. Yes, you can increase the brightness of your HDR backdrop by going into the rendering technique options in the Physically Based rendering technique and increasing the value of daytime or nighttime backdrop intensity (daytime for when the sun is turned on and nighttime for when it is off).

 

1 hour ago, basketballman said:

can you apply an emissiveness to its properties ?

The backdrop is used for lighting calculations in PBR, acting as emissive by default. Other rendering techniques do not support an emissive backdrop.

 

1 hour ago, Renerabbitt said:

Backdrop Intensity is the only thing that effects your backdrop, though with automatic exposure, your sun settings effect(percieved) it as well

Rene is correct here. The backdrop intensity is the only setting directly applied to backdrop lighting. In PBR with automatic exposure, turning up the brightness of the backdrop may not appear to make much of a difference in the lighting of the scene. This is because the perceived brightness of lights is relative to the brightness of other lights in how it is displayed on screen. For example, a room with a lamp might appear dark when viewed from outside, but then when moving the camera into the room, it appears to light up and the lamp seems much brighter. (The exposure adjusts automatically when entering a darker space). Similarly, the brightness of the sun or other light sources relative to your backdrop intensity will impact how much light seems to be coming from the backdrop. Therefore, turning the sun brightness down will make the backdrop seem brighter. If you want to get the most from your HDR backdrop, you can turn on the "Use Only Backdrop For Lighting" setting in the rendering technique options, which will essentially set the brightness of the sun to zero, so the majority of the light in the scene will come from the backdrop and it will appear brighter.

[kwhitt]

5 hours ago, Renerabbitt said:

Backdrop Intensity is the only thing that effects your backdrop, though with automatic exposure, your sun settings effect(percieved) it as well

Thanks Renee.  I see that now.

[kwhitt]

4 hours ago, Chief_Trent said:

Hi Kevin. Yes, you can increase the brightness of your HDR backdrop by going into the rendering technique options in the Physically Based rendering technique and increasing the value of daytime or nighttime backdrop intensity (daytime for when the sun is turned on and nighttime for when it is off).

 

The backdrop is used for lighting calculations in PBR, acting as emissive by default. Other rendering techniques do not support an emissive backdrop.

 

Rene is correct here. The backdrop intensity is the only setting directly applied to backdrop lighting. In PBR with automatic exposure, turning up the brightness of the backdrop may not appear to make much of a difference in the lighting of the scene. This is because the perceived brightness of lights is relative to the brightness of other lights in how it is displayed on screen. For example, a room with a lamp might appear dark when viewed from outside, but then when moving the camera into the room, it appears to light up and the lamp seems much brighter. (The exposure adjusts automatically when entering a darker space). Similarly, the brightness of the sun or other light sources relative to your backdrop intensity will impact how much light seems to be coming from the backdrop. Therefore, turning the sun brightness down will make the backdrop seem brighter. If you want to get the most from your HDR backdrop, you can turn on the "Use Only Backdrop For Lighting" setting in the rendering technique options, which will essentially set the brightness of the sun to zero, so the majority of the light in the scene will come from the backdrop and it will appear brighter.

@Chief_TrentThanks Trent.  It's good to know that turning off the sun (which I do often) requires that you increase the Nighttime Backdrop Intensity.

 

Maybe you can answer something for me.  Why do we have the ability to use both area lights and the point or spot light when it is already used in a fixture.  For example, I have created my own downlights (celling LED's) which have a spot light aimed at the floor.  In addition to this, the lens on this light has an emissive material applied.  I realize that the most accurate way is to use the area light from the lens solely (without the spot) or at least that is how it's done in other software I use.  However, when working with the area light alone, I must turn up the intensity of the lumens to an unreasonable amount to get the output I would expect to see (such as a 1,000 lumen ceiling light).  The area light alone needs to be set to 10k or more.  When the spot light and the area light are used together, the lumens seem to be more accurate.  What is the most accurate way in Chief to represent a 800 to 1,000 ceiling downlight.  In combination or area light alone?  Also, how does ticking "Apply Emissive and Color from Light(s)" factor in?  Does this retain true area lighting with the spot light settings driving the output?  Or am I even getting an area light when I do this?  This is not as straight forward as it is in other PBR software.  All I know is that when I use area lights alone, I am not getting the expected lumen output which leads me to believe I am doing something wrong.

[Renerabbitt]

27 minutes ago, kwhitt said:

I must turn up the intensity of the lumens to an unreasonable amount to get the output I would expect to see (such as a 1,000 lumen ceiling light)

Assuming you have automatic exposure, your "metering" is being changed, so either change the automatic exposure setting or switch to manual. With automatic, as you turn lumens up, it will be adapting to the overall light in your shot. 

[kwhitt]

3 minutes ago, Renerabbitt said:

Assuming you have automatic exposure, your "metering" is being changed, so either change the automatic exposure setting or switch to manual. With automatic, as you turn lumens up, it will be adapting to the overall light in your shot. 

Thanks for the reply.  I never use automatic exposure.  The lumens do not seem correct to me when using an area light on its own.

[Renerabbitt]

6 minutes ago, kwhitt said:

The lumens do not seem correct to me when using an area light on its own.

why don't you use automatic exposure?
in terms of it not looking correct, it shouldn't look correct, you would have to fake the geometry that would create your ies profile. We do not have any Ies profile compatibility so the actual geometry of the light would need to be produced in a way to fake the effect of proper beam spread, hot spotting, falloff etc. That's a tall order. Would switch to another software like thea if you are looking for that level of accuracy. 
Area lights are just taking the surface normal direction and if I were to guess, it probably takes the average surface normal direction as an equation to trace the path of light. Since usually we just have a mesh that is a flat plan such as a can light, the surface normal is straight down, so its not creating a cone at all. There is a lot more to this conversation but the short of it is that I would plan on editing in post or messing with manual exposure if you want more finite control

[kwhitt]

6 minutes ago, Renerabbitt said:

why don't you use automatic exposure?
in terms of it not looking correct, it shouldn't look correct, you would have to fake the geometry that would create your ies profile. We do not have any Ies profile compatibility so the actual geometry of the light would need to be produced in a way to fake the effect of proper beam spread, hot spotting, falloff etc. That's a tall order. Would switch to another software like thea if you are looking for that level of accuracy. 
Area lights are just taking the surface normal direction and if I were to guess, it probably takes the average surface normal direction as an equation to trace the path of light. Since usually we just have a mesh that is a flat plan such as a can light, the surface normal is straight down, so its not creating a cone at all. There is a lot more to this conversation but the short of it is that I would plan on editing in post or messing with manual exposure if you want more finite control

I don't use automatic exposure as it is impossible to balance the light correctly.  Lumens are now used to specify the total light output of a fixture regardless of the size or shape of the lens.  Unlike watts that is size dependent.  If the area light is indicated to be 800 lumens that's how much light it should emit.  That's not what I'm seeing in Chief when I use an area light on its own.  I am attempting to get clarification from Trent on why you can use the area lights in conjunction with a spot or point and how that affects the illumination.  I am not worried about the IES data of the fixture at this time although that would be nice - only the total light output.  I've been using Corona Renderer for over 15 years, and although Chief does not have many of the shader features such as SSS, I am getting very similar results with it without all the trouble of exporting to another software.  It's very close to a one software solution which saves me lots of time.

[Renerabbitt]

28 minutes ago, kwhitt said:

Trent on why you can use the area lights in conjunction with a spot or point and how that affects the illumination

They are not being used in conjunction in GPU raytrace views. It's one or the other. The Area Light can inherit the lumen value from your punctual lights and it does seem that the value is in lumens vs "brightness" from the material itself
In terms of lumen output, manual exposure I believe is just taking an average of your scene's pixel values and then adjusting from there. In other words, I don't believe that this is a static approach in any given view, it depends on the pixel illumination of the shot when considering ambient light etc. So your lumen output in terms of exposure doesn't really mean anything at all. Lumen values on backdrop A at intensity of 12000 is going to look different than backdrop B at 12000.
his would be a question for Ryan or Dan most likely. Maybe Trent knows as well.
 

[Ryan-M]

5 hours ago, kwhitt said:

@Chief_TrentThanks Trent.  It's good to know that turning off the sun (which I do often) requires that you increase the Nighttime Backdrop Intensity.

 

Maybe you can answer something for me.  Why do we have the ability to use both area lights and the point or spot light when it is already used in a fixture.  For example, I have created my own downlights (celling LED's) which have a spot light aimed at the floor.  In addition to this, the lens on this light has an emissive material applied.  I realize that the most accurate way is to use the area light from the lens solely (without the spot) or at least that is how it's done in other software I use.  However, when working with the area light alone, I must turn up the intensity of the lumens to an unreasonable amount to get the output I would expect to see (such as a 1,000 lumen ceiling light).  The area light alone needs to be set to 10k or more.  When the spot light and the area light are used together, the lumens seem to be more accurate.  What is the most accurate way in Chief to represent a 800 to 1,000 ceiling downlight.  In combination or area light alone?  Also, how does ticking "Apply Emissive and Color from Light(s)" factor in?  Does this retain true area lighting with the spot light settings driving the output?  Or am I even getting an area light when I do this?  This is not as straight forward as it is in other PBR software.  All I know is that when I use area lights alone, I am not getting the expected lumen output which leads me to believe I am doing something wrong.

 

Area lights and punctual lights on a single object are never used simultaneously.  If the "Use Area Lights" checkbox is checked (it is by default) then the emissive surfaces on the fixture produce light.  If it is not checked, then the punctual light sources produce light.

 

Punctual lights specify lumens which quantify total power output.  Emissive materials specify power per area (e.g. candela/square meter).  This makes it generally more difficult to work directly with emissivity.  An emissive material applied to a small bulb will produce significantly less light in your scene than the same material applied to a large bulb.

 

We wanted to allow people to continue to work with lumens. The "Apply Emissive and Color from Light(s)" checkbox allows the emissivity of the emissive material(s) on a fixture to be derived from the lumens specified in the punctual lights on the fixture.  If you have a fixture with a single point light that produces 1200 lumens and the "Apply Emissive and Color from Light(s)" checkbox is checked, then Chief will automatically calculate the appropriate emissivity of the emissive materials on the fixture such that all of the emissive surfaces on the fixture output a total of 1200 lumens.  The point light itself won't cast light, but its intensity (and color) will inform the properties of the emissive surfaces that make up the area light.

 

When "Apply Emissive and Color from Light(s)" is checked, Chief uses the sum of the punctual light sources on a fixture as the means by which you dictate the total power output of a fixture.

 

When you uncheck that box and directly configure the emissivity of a material you're no longer working in lumens, and it is correct that you will have to specify values much larger than typical lumen values in order to get the same results.  In general, I would recommend leaving that checkbox checked.

[kwhitt]

8 hours ago, Renerabbitt said:

They are not being used in conjunction in GPU raytrace views. It's one or the other. The Area Light can inherit the lumen value from your punctual lights and it does seem that the value is in lumens vs "brightness" from the material itself
In terms of lumen output, manual exposure I believe is just taking an average of your scene's pixel values and then adjusting from there. In other words, I don't believe that this is a static approach in any given view, it depends on the pixel illumination of the shot when considering ambient light etc. So your lumen output in terms of exposure doesn't really mean anything at all. Lumen values on backdrop A at intensity of 12000 is going to look different than backdrop B at 12000.
his would be a question for Ryan or Dan most likely. Maybe Trent knows as well.
 

Thanks Renee.  I find the Light Data DBX confusing for reasons I'll state in a separate post to Ryan.  I've taken several interior courses on the use of Vray and Corona Renderer over the years from some well-known artists in those communities and they always speak of calibrating the scene for natural lighting first and then adding your interior accent lights (if appropriate).  This way you know your exposure is using real world settings which will allow the materials (shaders) to interact properly.  Neither of these renderers by Chaos Group have an "automatic exposure" setting or at least they didn't up until a year ago when I stopped using them.  I've only encountered this feature in TwimMotion and Chief.  Using automatic exposure would negate the process I describe above as you would never know if the scene was calibrated correctly.  That said, I'm not sure if Chief's Sun and default setting of 7000 under "Daytime Backdrop Intensity" represent any real world values.  I would imagine they do but have no idea what they are.

[kwhitt]

4 hours ago, Ryan-M said:

 

Area lights and punctual lights on a single object are never used simultaneously.  If the "Use Area Lights" checkbox is checked (it is by default) then the emissive surfaces on the fixture produce light.  If it is not checked, then the punctual light sources produce light.

 

Punctual lights specify lumens which quantify total power output.  Emissive materials specify power per area (e.g. candela/square meter).  This makes it generally more difficult to work directly with emissivity.  An emissive material applied to a small bulb will produce significantly less light in your scene than the same material applied to a large bulb.

 

We wanted to allow people to continue to work with lumens. The "Apply Emissive and Color from Light(s)" checkbox allows the emissivity of the emissive material(s) on a fixture to be derived from the lumens specified in the punctual lights on the fixture.  If you have a fixture with a single point light that produces 1200 lumens and the "Apply Emissive and Color from Light(s)" checkbox is checked, then Chief will automatically calculate the appropriate emissivity of the emissive materials on the fixture such that all of the emissive surfaces on the fixture output a total of 1200 lumens.  The point light itself won't cast light, but its intensity (and color) will inform the properties of the emissive surfaces that make up the area light.

 

When "Apply Emissive and Color from Light(s)" is checked, Chief uses the sum of the punctual light sources on a fixture as the means by which you dictate the total power output of a fixture.

 

When you uncheck that box and directly configure the emissivity of a material you're no longer working in lumens, and it is correct that you will have to specify values much larger than typical lumen values in order to get the same results.  In general, I would recommend leaving that checkbox checked.

Ryan - Thanks for clarifying.  Please see attached Light Data DBX.  At the very top “Use Area Light(s)” is checked.  With Light 1 selected at the top, you have the option at the very bottom to check “On in Default Light Set”.  So, I assumed both types of lights were emitting or why have this option?  It would seem to me that by checking “Use Area Light(s)”, the ability to select Light 1 would be grayed out.  And Light 1 is shown to be used in “All Views” at the top.  So, “All Views” at the top would apply to only non-GPU RT types of rendering?

 

What happens if “On in Default Set” is not checked for Light 1?  Will the area light still inherit the properties of Light 1 and calculate the emissive in lumens if the material’s "Apply Emissive and Color from Light(s)" is checked?

[Renerabbitt]

7 hours ago, kwhitt said:

"automatic exposure"

I imagine that the main purpose for this is that many people wont take the time to properly light an entire model when they are scoping one room.

 

7 hours ago, kwhitt said:

automatic exposure would negate the process I describe above as you would never know if the scene was calibrated correctly

Automatic exposure can certain effect an underexposed scene but it wont allow you to blow out the scene. This is similar to actually shooting in real life on a DSLR in auto-exposure and metering. I understand that you prefer the manual exposure
 

 

7 hours ago, kwhitt said:

7000 under "Daytime Backdrop Intensity" represent any real world values

It certainly represent something, haha, I imagine that is is scalar to radiance per pixel on the HDRI and that number is a mean of the provided HDRI's in the catalog to show proper luminance in a scene. I do not believe that there is any internal build of chief that does photometric analysis, or at least none that I have heard of.
 

 

7 hours ago, kwhitt said:

both types of lights were emitting or why have this option? 

If you don't mind I am going to answer these questions to Ryan. Sometimes its hard to bring him back as many of the devs dont look here that often or so they say.
I agree this is confusing, but it is just to distinguish area lights from punctual lights by classification. It's just to say that punctual lights work in all views and area lights do not, which leads into the help menus. Especially important for those bringing in their own fixtures and not setting their punctual lights z offset for instance and wondering why their PBR looks great but there standard view has weird shadows.
 

 

7 hours ago, kwhitt said:

by checking “Use Area Light(s)”, the ability to select Light 1 would be grayed out

but then we would not be able to set lumens or color values which the area light can derive its settings from

 

 

7 hours ago, kwhitt said:

And Light 1 is shown to be used in “All Views” at the top.  So, “All Views” at the top would apply to only non-GPU RT types of rendering?

only when "Use Area Lights" is checked, which I agree is confusing
 

 

7 hours ago, kwhitt said:

What happens if “On in Default Set” is not checked for Light 1?  Will the area light still inherit the properties of Light 1 and calculate the emissive in lumens if the material’s "Apply Emissive and Color from Light(s)" is checked?

Yes it will, but the light will not be on and will not be emitting any light nor will it appear to be on or creating bloom in the Light Set called Default Light Set. This would only affect any camera that is using the Default Light Set


 

[kwhitt]

18 minutes ago, Renerabbitt said:

@RenerabbittThanks, Rene.  You've saved me much time not having to experiment.  I appreciate the help!

 

 

[Ryan-M]

8 hours ago, kwhitt said:

At the very top “Use Area Light(s)” is checked.  With Light 1 selected at the top, you have the option at the very bottom to check “On in Default Light Set”.  So, I assumed both types of lights were emitting or why have this option?  It would seem to me that by checking “Use Area Light(s)”, the ability to select Light 1 would be grayed out.  And Light 1 is shown to be used in “All Views” at the top.  So, “All Views” at the top would apply to only non-GPU RT types of rendering?

The top of the dialog allows you to configure how the fixture should produce light.  "On in Default Light Set" basically turns the light on in the default light set (so the light will cast light in any views using that light set).

 

We don't disable the punctual lights even when using an area light for a couple of reasons:

• The punctual lights can be used to configure the power output of the fixture (e.g. when "Apply Emissive and Color from Light(s)" is checked).  
• Area lights are only used in Ray Traced PBR views.  The punctual lights are still used in all other views.  We don't generally disable user interface in dialogs like this in a way that is dependent on the view the dialog was opened from.

There is a lot of complexity added to the dialog due to it needing to facilitate non-PBR techniques, hardware that doesn't support ray tracing, etc.

 

8 hours ago, kwhitt said:

What happens if “On in Default Set” is not checked for Light 1?  Will the area light still inherit the properties of Light 1 and calculate the emissive in lumens if the material’s "Apply Emissive and Color from Light(s)" is checked?

 

Yes.  You can think of "On in Default Set" as "can potentially cast light in the default light set", where part of the criteria for satisfying that potential is whether or not you're in Ray Traced PBR and the fixture is set to Use Area Lights.

 

8 hours ago, kwhitt said:

Using automatic exposure would negate the process I describe above as you would never know if the scene was calibrated correctly.

 

The purpose of automatic exposure is to allow you to move the camera around and/or between lighting environments without needing to reconfigure exposure settings.  It simply tries to keep the output within a reasonable/viewable range as a function of the overall intensity of the rendered scene.  You are correct that it can make it difficult to "correctly" calibrate lighting.  If you're tuning a particular scene and your camera is static, then manually configuring exposure makes a lot of sense.

 

8 hours ago, kwhitt said:

That said, I'm not sure if Chief's Sun and default setting of 7000 under "Daytime Backdrop Intensity" represent any real world values.

 

Backdrop intensity values are interpreted as Luminance.

[kwhitt]

4 hours ago, Ryan-M said:

The top of the dialog allows you to configure how the fixture should produce light.  "On in Default Light Set" basically turns the light on in the default light set (so the light will cast light in any views using that light set).

 

We don't disable the punctual lights even when using an area light for a couple of reasons:

• The punctual lights can be used to configure the power output of the fixture (e.g. when "Apply Emissive and Color from Light(s)" is checked).  
• Area lights are only used in Ray Traced PBR views.  The punctual lights are still used in all other views.  We don't generally disable user interface in dialogs like this in a way that is dependent on the view the dialog was opened from.

There is a lot of complexity added to the dialog due to it needing to facilitate non-PBR techniques, hardware that doesn't support ray tracing, etc.

 

 

Yes.  You can think of "On in Default Set" as "can potentially cast light in the default light set", where part of the criteria for satisfying that potential is whether or not you're in Ray Traced PBR and the fixture is set to Use Area Lights.

 

 

The purpose of automatic exposure is to allow you to move the camera around and/or between lighting environments without needing to reconfigure exposure settings.  It simply tries to keep the output within a reasonable/viewable range as a function of the overall intensity of the rendered scene.  You are correct that it can make it difficult to "correctly" calibrate lighting.  If you're tuning a particular scene and your camera is static, then manually configuring exposure makes a lot of sense.

 

 

Backdrop intensity values are interpreted as Luminance.

Thanks Ryan.  Very helpful and it makes sense.  Kevin