| Please note that this is a BETA version of the document. All information presented is correct but we are working on improving the details. |
Introduction
This article is about adding and tweaking shadows that are projected by the talent onto the virtual scene. (Or in other words, shadows cast by the billboard.) This article does not describe how to set up shadows for your virtual scene. For this, please refer to these documents:
More on setting up shadows in 3D sets in Aximmetry:
More on setting up shadows in 3D sets in Unreal Engine: https://docs.unrealengine.com/4.27/en-US/BuildingWorlds/LightingAndShadows/
We will discuss two separate cases:
- virtual cameras
- tracked cameras
Virtual Camera
Setting up shadows in your production should be the last step in your process, so in this article we assume, that you have already set up your billboard (position, keying, input cropping, etc.) properly and you are familiar with the BILLBOARDS control board. If not, please find more info here:
In the BILLBOARDS control board, select BILLBOARD.
In the pin values panel, you will find several options to adjust shadows to achieve the required quality of your production.
Cast Shadows
Note: in this section, we will show the settings with the Show AO setting turned Off, to show the difference better and help with the adjustments. However, in your final setup, this should be turned On. More on the Show AO feature in the next chapter.
If this option is turned on, the virtual lights in your scene will be blocked by the talent's image on the billboard, casting shadows on parts of the scene (and on other billboards as well).
This will make your scene more realistic making the billboard with the talent appear much more part of the virtual surroundings
Here, the Cast Shadow property is turned off.
and here, turned On.
In connection to the Cast Shadow setting, there are 3 values you can adjust:
Shadow Rotation
Rotates the shadow in the plane of the virtual floor.
This tool is used to better match the angle of the shadow to the billboard and the virtual lights in your scene. The shadow automatically rotates, when the billboard rotates, but you can use this feature to fine-tune the angle.
Here the shadow is rotated so much, that it is barely visible:
And here, not rotated enough, so it looks like the talent was lit completely from the front:
Both of these are incorrect since in our example the virtual light is closer to a 45-degree angle to the billboard, so let's try a value in between the two:
Typical values: 0 - 1.
Shadow Offset
Moves the shadow in the plane of the virtual floor.
The shadow is moved with the billboard, but there might be cases when you would like to further adjust the position of the shadow. By default, the shadow might appear a bit off of the talent.
Using the Shadow Offset, looking at the contact of the shoes and the floor, and the position of the legs, you can move the shadow to the proper location.
Typical values: -0.05 - +0.05 | -0.1 - -0.05
Shadow Depth
Adds thickness to the shadow.
This feature is useful if the billboard is lit from sideways. In reality, the talent has a thickness, but the billboard is flat, so if you light the billboard from the side, the shadow looks like a line, or it is simply too narrow and does not have the proper thickness, which is not realistic.
You can increase the shadow depth a bit, to give the shadow more thickness or "depth" for a better, more 3D look.
Typical values: 0 - 0.25
Show AO
Note: we will turn off the Cast Shadows setting while we set up AO.
AO means Ambient Occlusion. This shadow generally appears at places where different objects contact, or are close to each other. A good example of this is if you look at any upper corner of your room. The corner appears darker than the surroundings. There is also AO where your shoes touch the floor, hence turning this feature ON will help viewers perceive the placement of the talent in the virtual scene as more realistic.
If this is turned on, a contact shadow will be placed directly under the talent on the billboard.
And here, it is turned off.
In this image, the talent looks as if he was floating above the floor of the virtual scene.
Here, the Show AO property is turned on.
You can see the Aximmetry creates the AO from the image of the talent on the billboard, that is why the shadow looks like the talent a bit, but of course with some distortion.
Note:
If the show AO property is turned on, but you don't see the shadow below the talent, then try adjusting the height of your billboard with the Y parameter of the Transformation property.
When the height is not set properly, the shadow is 'under' the floor.
Other AO settings
We suggest setting up the AO in the following order.
AO Opacity
Changes the opacity of the AO.
A higher value means stronger AO. The value of this property depends on how strong the direct lights are which are pointed at the talent. If the lights are harsh and strong, then the value should be lower. If your scene is darker and there is less light on the talent, you can set it to a higher value.
Bad examples (too low
& too high values)
good example
Typical values: 0.2 - 0.6
AO Blur
Blurs the shadow radially.
As mentioned before, the AO is generated from the talent's image on the billboard. If you set this value to 0, you will see this clearly.
Of course, this is very unrealistic, so we need to blur the shadow by increasing the value.
We have also mentioned that the AO is actually a contact shadow, this is still not blurred enough, because on the right you can still see the talent's extended arm, which is way above the ground level, so we increase it a bit more.
This is better, but we could add a bit more strength to it. You can go back to AO Opacity setting and increase the value a bit.
Typical values: 0.5 - 2.5
AO Front Offset
This value moves the shadow in a direction perpendicular to the billboard (back and forth).
When setting this value, you have to keep in mind the position of the light above the talent. If the light is more to the front, the AO should be a bit more behind, if the light is behind, the AO should be a bit more in front of the talent.
Be careful not to offset the AO too much.
Try to keep the AO closer to the billboard, and only offset it a bit to the back or to the front.
Typical values: -0.2 to +0.2 If the lights are behind the talent, the value should be positive.
AO Front Scale
Stretches the shadow in a direction perpendicular to the billboard (back and forth).
When setting this value, you have to keep in mind the position of the light above the talent. If the light is closer to the talent, the AO will become 'fatter'. If it is further above the head of the talent, it will be flatter.
If we set the value too low the shadow will be too flat
If it's too high, the shadow extends way behind and in front of the talent
Find a value between the two.
Typical values: 0.1 - 0.35, depending on how high and/or in front or behind the talent the lights are in the studio.
AO Side Offset
Moves the shadow in a parallel direction to the billboard (sideways).
Setting this value, you have to consider the position of the virtual light in your scene. You should push the shadow a bit more to the other side of the talent, than where the light is coming from.
In this example the light is on the left side of the talent, so placing the shadow also on the left, does not look good.
You should rather set it to the other side
Typical values: 0.25 - 0.5
AO Width
Stretches the shadow parallel to the billboard.
We use this feature to adjust the width of the AO.
In this image, you can see that the AO is way wider than the talent
If we decrease the value too much, the shadow will be weirdly thin.
So we will find a value between the two. We aim for the shadow to be just a bit wider than the talent's stance.
Typical values: 0.5 - 2
AO Fatten
Combines the AO Front Scale and AO Width, so you can adjust both at the same time.
Typical values: 2 - 6
Final Result
The final result of your shadow setup should look something like this:
Note, that the shadows are not too dark and are positioned according to the light source.
Also, we used the AO to cover the small difference between the talent's left heel and its shadow.
Billboard rotation
You will see that with the virtual camera movements (if the Look At Camera setting is set to At Camera or At Camera Plane), the billboard rotates in order to keep the shape of the talent on the billboard intact. However, the cast shadows don't rotate (the AO does). This is on purpose since the position of the virtual light(s) do(es) not change, so the shadow has to stay the same.
If you see that the cast shadow and the talent's image on the billboard separate noticeably, your virtual camera path should be adjusted. We generally suggest slow and slight virtual camera movements, just like with a studio camera.
Tracked Camera
Since setting up shadows is one of the last steps in your production line before the show, we assume that your camera tracking and lens calibration are properly set up.
If this is not the case, please refer to this documentation:
In order for Aximmetry to generate a shadow of the talent, we must project the tracked camera's image onto a billboard.
For a full description of how to enable and use Billboards with tracked cam compounds, please refer to this document:
Billboards
In tracked camera compounds, you won't find the BILLBOARDS control board. Instead, you can find INPUTS.
The workflow of the INPUTS control board is similar to the BILLBOARDS control board, but there are of course some differences.
You will find the Billboard panels here:
After selecting the Billboard #* panel, you will find the pin values regarding to setting up shadows in the Pin Values tab.
Cast Shadow
Turn ON Cast Shadows
Similar to the case with a Virtual Camera, Aximmetry will generate a shadow based on the placement of lights and the position of the billboard in your scene,
but in order to set the shadows up properly, the tracked cam compound allows the following settings to be adjusted:
Please refer to the virtual cam compound shadow settings chapter for more info on these settings.
