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Pyro Bake Volume provides controls to enhance the look of a pyro solve in the viewport. It also handles automatic material assignment to best match the rendering results to the viewport display, and is designed to provide a similar interface to the Pyro Shader. When scattering is turned on, it bakes out a
scatter volume that is used by the Pyro Shader to approximate the look of light scattering inside the explosions.
Using Pyro Bake Volume with the Pyro Shader
The Pyro Bake Volume node contains a Pyro Shader, which is automatically assigned to the processed volumes. The embedded shader references parameters on Pyro Bake Volume to ensure that the render matches the viewport. Therefore, you can create copies of the Pyro Bake Volume node and render different variants without adjusting material assignments at the object level.
You can dive inside the Pyro Bake Volume node to access the Pyro Shader and its controls.
Although most of the Pyro Shader’s features are available on the Pyro Bake Volume node, there are a few extra parameters on the shader that are not available in the viewport. To see the effect of these parameters, you need to render the volumes.
The following are additional things you can control with the Pyro Shader.
Clamp or remap the smoke density, or scale it by another volume (such as
temperature) with the Use Control Volume parameter.
Set the Smoke Brightness.
Change the color of the smoke using absorption with the Absorption Color parameter.
Change the color of the shadows with the Shadow Color parameter.
Set the Scattering Phase.
When Auto Update is enabled on the Render View, the render update can be slower with heavier volumes, since the underlying geometry has to recook on every parameter change to update viewport visualization attributes.
When you break material references using the Quick Setups menu, the assigned material becomes independent of the Pyro Bake Volume’s parameters. This lets you adjust material parameters without recooking the SOP geometry, speeding up renders. However, render and viewport looks will be different, since shader parameter changes aren’t propagated to the Pyro Bake Volume node.
Certain combinations of settings (for example, multiple emissive elements) cannot be directly visualized in the viewport given the functionality of Volume Visualization. In these cases, a combined Emission Volume (
Ce by default) is created internally to help with visualization. When this happens, the node will display a message that a different output is visualized, and displaying the geometry downstream will produce a different look in the viewport.
When Enable Scatter is on, Pyro Bake Volume will generate a special scatter volume for the shader. The scatter volume aims to imitate internal scattering of emitted light. You can use the parameters on the Scatter tab to control the primary emission and scattering. To compute the scatter field, the Source Volume is first converted to emission colors; this intermediate field is then blurred to spread out the emission.
Since scatter has to be calculated before rendering, its color (set by parameters in the Color section) and softness (set by settings in the Blur section) are controlled from this node and not from the Pyro Shader.
Setting up scattering
Turn on Enable Scatter on the Scatter tab.
Turn off Enable Mask to visualize the full extent of the scatter without masking.
Know your maximum
temperaturevalues on the frames you are testing, and adjust Source Range accordingly.
By increasing the minimum value of Source Range, you will cut off the low temperature values so they will not contribute to the scattered emission.
First set the maximum value of the Source Range. To find an appropriate setting, you can begin by calculating the maximum
temperaturevalue over a few sample frames. The average of these values can serve as a starting value, and you can tweak it further to fine-tune the look.
Adjust Scale and Hot Core Scale for the intensity of the scatter.
Change the amount of blurring based on the size of your simulation. Turn on Use Blur Steps to further smooth out the scatter area.
Examine frames from the beginning, middle, and end of your simulation while refining the aforementioned parameters.
Turn on Enable Mask and find values for Mask Center and Mask Width that produce the desired results in the viewport. Alternatively, you can break the material reference and examine renders as you tweak parameters on the assigned shader.
All range settings should consider the range of values in their respective bound volumes. The Pyro Solver will write the minimum and maximum values for each exported volumes into primitive attributes when Compute Min/Max Values is enabled on the Export tab.
This menu lets you run some simple scripted setups to help with the most common tasks.
Creates a Pyro Shader material at the selected location with parameters referencing this node. This will update the Assign Material field with the newly created shader.
Break Material References
Breaks all references to this node on the material set by Assign Material.
Creates an Environment and a Directional Light at the object-level with a selected preset. This is useful to quickly create lights to improve the look of the pyro simulation in the viewport.
Creates all necessary nodes to quickly get you started with rendering in Mantra. This includes environment and volume lights, as well as a mantra render node. It also enables motion blur on the render target (Geometry Velocity Blur in the Render → Sampling tab of the object-level node).
Create Render Stage
Creates all necessary nodes to quickly get you started with rendering. This includes environment and volume lights in LOPs with Karma. When looking through a camera upon selecting this entry, the selected camera will be imported to LOPs. Otherwise, a new camera will be created based on the viewer’s position.
Creates a File Cache node that is setup to cache a pyro simulation.
Sets the parameters on this node with a more artistic preset by using color ramps to map
temperature to emission and enable scattering.
Creates a more traditional setup that uses blackbody curves to derive a physical emission
The path to the shader that is assigned to the volumes. The
shop_materialpath primitive attribute will point to the specified material, ensuring that it is used for renders. This will take precedence over any assigned material at the object level. Turn this off if you do not want to assign a material at the SOP level.
Max Vis Resolution
When turned on, it ensures reasonably fast shading times for lighting and avoids running into texture memory problems in the viewport. Use this for faster pre-visualization.
Enables the smoke aspect of the volume. Smoke absorbs and attenuates light traveling through it. Use Smoke Volume to identify the volume storing the smoke’s density.
Controls the overall density of the smoke. Increasing this value will give the smoke a thicker appearance. Reducing it will make the smoke less opaque.
Controls the overall color of the smoke. To get more natural looking smoke, change the menu on the right side of this parameter from Constant to Use Ramp. This will allow you to vary the smoke’s color with its density.
The minimum and maximum density values to map to the left and right endpoints of the Smoke Color Ramp.
Computes the minimum and maximum range values of the selected volume on the current frame. Use this to get an idea of your maximum field value.
Smoke Color Ramp
This ramp controls how the smoke’s density values are mapped to its color. The horizontal axis of the Smoke Color Ramp spans the Density Range. For example, you can use this ramp to make the smoke have a darker color where it is more dense.
Controls the color of shadows cast by the smoke. The complements of these values act like additional density multipliers for light of each color (red, green, or blue).
This multiplier applies on top of Density Scale when the volumes are lit. Increasing this value will result in less light penetrating the volume, without affecting the smoke’s opacity to the viewer. Decreasing this value reduces the light’s absorption, without changing how opaque the smoke appears.
Ambient Shadow Scale
Determines the intensity of self shadows from ambient light sources. The final amount of self-shadowing from these lights is controlled by the product of Density Scale, Shadow Scale, and Ambient Shadow Scale. The video demonstrates the value increasing from 0 to 1.
Turning off this checkbox does not disable ambient shadowing. Instead, it keeps this property of the geometry unchanged. If no Ambient Shadow Scale is set, Ambient Occlusion on the Geometry tab of the Display Options controls the default amount of self-shadowing from ambient lights.
The default headlight is treated as an ambient source by fog volumes.