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The Projector 3D node is used to project an image upon 3D geometry. This can be useful in many ways: texturing objects with multiple layers, applying a texture across multiple separate objects, projecting background shots from the camera’s viewpoint, image-based rendering techniques, and more. The Projector node is just one of several nodes capable of projecting images and textures. Each method has advantages and disadvantages.
Projected textures can be allowed to “slide“ across the object if the object moves relative to the Projector 3D, or, alternatively, by grouping the two with a Merge 3D so they can be moved as one and the texture remains locked to the object.
The Projector 3D node’s capabilities and restrictions are best understood if the Projector is considered to be a variant on the SpotLight node. The fact that the Projector 3D node is actually a light has several important consequences when used in Light or Ambient Light projection mode:
- Lighting must be turned on for the results of the projection to be visible.
- The light emitted from the projector is treated as diffuse/specular light. This means that it is affected by the surface normals and can cause specular highlights. If this is undesirable, set the Projector 3D to project into the Ambient Light channel.
- Enabling Shadows causes Projector 3D to cast shadows.
- Just as with other lights, the light emitted by a Projector 3D only affects objects that feed into the first Merge 3D that is downstream of the Projector 3D node in the node tree.
- Enabling Merge 3D’s Pass Through Lights checkbox allows the projection to light objects further downstream.
- The light emitted by a Projector 3D is controlled by the Lighting options settings on objects and the Receives Lighting options on materials.
- Alpha values in the projected image do not clip geometry in Light or Ambient Light mode. Use Texture mode instead.
- If two projections overlap, their light contributions are added.
To project re-lightable textures or textures for non-diffuse color channels (like Specular Intensity or Bump), use the Texture projection mode instead:
- Projections in Texture mode only strike objects that use the output of the Catcher node for all or part of the material applied to that object.
- Texture mode projections clip the geometry according to the Alpha channel of the projected image.
See the section for the Catcher node for additional details.
Camera Projection vs. Projection 3D Node
The Camera 3D node also provides a projection feature, and should be used when the projection is meant to match a camera, as this node has more control over aperture, film back, and clip planes. The Projector 3D node was designed to be used as a custom light in 3D scenes for layering and texturing. The projector provides better control over light intensity, color, decay, and shadows.
Projector 3D Node Inputs
The Projector 3D has two inputs: one for the scene you are projecting on to and another for the projected image.
- SceneInput: The orange scene input accepts a 3D scene. If a scene is connected to this input, then transformations applied to the spotlight also affect the rest of the scene.
- ProjectiveImage: The white input expects a 2D image to be used for the projection. This connection is required.
Projector 3D Node Setup
As an example, the Projector 3D node below is used to project a texture (MediaIn2) onto 3D primitives as a way to create a simple 3D set. All the set elements are connected into a Merge 3D, which outputs the projected set into a larger scene with camera, lights, and other elements. As an alternative, the Projector 3D node could be inserted between the two Merge 3D nodes; however, the transform controls in the Projector 3D node would then affect the entire scene.
Projector 3D Node Controls Tab
When this checkbox is enabled, the projector affects the scene. Disable the checkbox to turn off the projector. This is not the same as the red switch in the upper-left corner of the Inspector. The red switch disables the tool altogether and passes the image on without any modification. The Enabled checkbox is limited to the effect part of the tool. Other parts, like scripts in the Settings tab still process as normal.
The input image is multiplied by this color before being projected into the scene.
Use this slider to set the Intensity of the projection when the Light and Ambient Light projection modes are used. In Texture mode, this option scales the Color values of the texture after multiplication by the color.
- Decay Type
A projector defaults to No Falloff, meaning that its light has equal intensity on geometry, despite the distance from the projector to the geometry. To cause the intensity to fall off with distance, set the Decay type to either Linear or Quadratic modes.
The Cone Angle of the node refers to the width of the cone where the projector emits its full intensity. The larger the angle, the wider the cone angle, up to a limit of 90 degrees.
- Fit Method
The Fit Method determines how the projection is fitted within the projection cone.
The first thing to know is that although this documentation may call it a “cone,” the Projector 3D and Camera 3D nodes do not project an actual cone; it’s more of a pyramid of light with its apex at the camera/projector. The Projector 3D node always projects a square pyramid of light—i.e., its X and Y angles of view are the same. The pyramid of light projected by the Camera 3D node can be non-square depending on what the Film Back is set to in the camera. The aspect of the image connected into the Projector 3D/Camera 3D does not affect the X/Y angles of the pyramid, but rather the image is scaled to fit into the pyramid based upon the fit options.
When both the aspect of the pyramid (AovY/AovX) and the aspect of the image (height * pixelAspectY)/ (width * pixelAspectX) are the same, there is no need for the fit options, and in this case the fit options all do the same thing. However, when the aspect of the image and the pyramid (as determined by the Film Back settings in Camera 3D) are different, the fit options become important.
For example, Fit by Width fits the width of the image across the width of the Camera 3D pyramid. In this case, if the image has a greater aspect ratio than the aspect of the pyramid, some of the projection extends vertically outside of the pyramid.
There are five options:
- Inside: The image is uniformly scaled so that its largest dimension fits inside the cone. Another way to think about this is that it scales the image as big as possible subject to the restriction that the image is fully contained within the pyramid of the light. This means, for example, that nothing outside the pyramid of light ever receives any projected light.
- Width: The image is uniformly scaled so that its width fits inside the cone. Note that the image could still extend outside the cone in its height direction.
- Height: The image is uniformly scaled so that its height fits inside the cone. Note that the image could still extend outside the cone in its width direction.
- Outside: The image is uniformly scaled so that its smallest dimension fits inside the cone. Another way to think about this is that it scales the image as small as possible subject to the restriction that the image covers the entire pyramid (i.e., the pyramid is fully contained within the image). This means that any pixel of any object inside the pyramid of light always gets illuminated.
- Stretch: The image is non-uniformly scaled, so it exactly covers the cone of the projector.
- Projection Mode
- Light: Projects the texture as a diffuse/specular light.
- Ambient Light: Uses an ambient light for the projection.
- Texture: When used in conjunction with the Catcher node, this mode allows re-lightable texture projections. The projection strikes only objects that use the catcher material as part of their material shaders.
One useful trick is to connect a Catcher node to the Specular Texture input on a 3D Material node (such as a Blinn). This causes any object using the Blinn material to receive the projection as part of the specular highlight. This technique can be used in any material input that uses texture maps, such as the Specular and Reflection maps.
Since the projector is based on a spotlight, it is also capable of casting shadows using shadow maps. The controls under this reveal are used to define the size and behavior of the shadow map.
- Enable Shadows: The Enable Shadows checkbox should be selected if the light is to produce shadows. This defaults to selected.
- Shadow Color: Use this standard Color control to set the color of the shadow. This defaults to black (0, 0, 0).
- Density: The Shadow Density determines the transparency of the shadow. A density of 1.0 produces a completely transparent shadow, whereas lower values make the shadow transparent.
- Shadow Map Size: The Shadow Map Size control determines the size of the bitmap used to create the shadow map. Larger values produce more detailed shadow maps at the expense of memory and performance.
- Shadow Map Proxy: The Shadow Map Proxy determines the size of the shadow map used for proxy and auto proxy calculations. A value of 0.5 would use a 50% shadow map.
- Multiplicative/Additive Bias: Shadows are essentially textures applied to objects in the scene, so there is occasionally Z-fighting, where the portions of the object that should be receiving the shadows render over the top of the shadow instead.
- Multiplicative and Additive Bias: Bias works by adding a small depth offset to move the shadow away from the surface it is shadowing, eliminating the Z-fighting. Too little bias and the objects can self-shadow themselves. Too much bias and the shadow can become separated from the surface. Adjust the multiplicative bias first, then fine tune the result using the additive bias control.
- Force All Materials Non-Transmissive: Normally, an RGBAZ shadow map is used when rendering shadows. By enabling this option, you are forcing the renderer to use a Z-only shadow map. This can lead to significantly faster shadow rendering while using a fifth as much memory. The disadvantage is that you can no longer cast “stained-glass”-like shadows.
- Shadow Map Sampling: Sets the quality for sampling of the shadow map.
- Softness: Soft edges in shadows are produced by filtering the shadow map when it is sampled. Fusion provides three separate filtering methods that produce different effects when rendering shadows.
- None: Shadows have a hard edge. No filtering of the shadow map is done at all. The advantage of this method is that you only have to sample one pixel in the shadow map, so it is fast.
- Constant: Shadow edges have a constant softness. A filter with a constant width is used when sampling the shadow map. Adjusting the Constant Softness slider controls the size of the filter. Note that the larger you make the filter, the longer it takes to render the shadows. If the Softness is set to constant, then a Constant slider appears. It can be used to set the overall softness of the shadow.
- Variable: The softness of shadow edges grows the farther away the shadow receiver is from the shadow caster. The variable softness is achieved by changing the size of the filter based on the distance between the receiver and caster. When this option is selected, the Softness Falloff, Min Softness and Max Softness sliders appear.
|The Softness Falloff slider appears when the Softness is set to variable. This slider controls how fast the softness of shadow edges grows with distance. More precisely, it controls how fast the shadow map filter size grows based on the distance between shadow caster and receiver. Its effect is mediated by the values of the Min and Max Softness sliders.
|The Min Softness slider appears when the Softness is set to variable. This slider controls the Minimum Softness of the shadow. The closer the shadow is to the object casting the shadow, the sharper it is up to the limit set by this slider.
|The Max Softness slider appears when the Softness is set to variable. This slider controls the Maximum Softness of the shadow. The farther the shadow is from the object casting the shadow, the softer it is up to the limit set by this slider.
Projector 3D Node Transform and Settings Tabs
The remaining Transform and Settings tabs are common to many 3D nodes. These common controls are described in detail HERE
About the Author
Justin Robinson is a Certified DaVinci Resolve, Fusion & Fairlight instructor who is known for simplifying concepts and techniques for anyone looking to learn any aspect of the video post-production workflow. Justin is the founder of JayAreTV, a training and premade asset website offering affordable and accessible video post-production education. You can follow Justin on Twitter at @JayAreTV YouTube at JayAreTV or Facebook at MrJayAreTV
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