As mentioned earlier, one of the core ingredients of the perception workflow is the randomization of various aspects of the simulation, in order to introduce sufficient variation into the generated data.
To start randomizing your simulation you will first need to add a `Scenario` to your scene. Scenarios control the execution flow of your simulation by coordinating all `Randomizer` components added to them. The Perception package comes with a useful set of Randomizers that let you quickly place your foreground objects in the Scene, generate varied backgrounds, as well as randomize various parameters of the simulation over time, including things such as position, scale, and rotation of objects, number of objects within the camera's view, and so on. Randomizers achieve this through coordinating a number of `Parameter`s, which essentially define the most granular randomization behaviors. For instance, for continuous variable types such as floats, vectors, and colors, Parameters can define the range, sampling distribution, and seed for randomization. This is while another class of Parameters let you randomly select one out of a number of categorical options.
To start randomizing your simulation you will first need to add a `Scenario` to your scene. Scenarios control the execution flow of your simulation by coordinating all `Randomizer` components added to them. The Perception package comes with a useful set of Randomizers that let you quickly place your foreground objects in the Scene, generate varied backgrounds, as well as randomize various parameters of the simulation over time, including things such as position, scale, and rotation of objects, number of objects within the camera's view, and so on. Randomizers achieve this through coordinating a number of `Parameter`s, which essentially define the most granular randomization behaviors. For instance, for continuous variable types such as floats, vectors, and colors, Parameters can define the range and sampling distribution for randomization. This is while another class of Parameters let you randomly select one out of a number of categorical options.
To summarize, a sample `Scenario` could look like this:
The background Prefabs are primitive shapes devoid of color or texture. Later Randomizers will take care of those aspects.
* **Action**: Set the rest of the properties (except for `Seed`) according to the image below. That is, `Depth = 0, Layer Count = 2, Separation Distance = 0.5, Placement Area = (6,6)`. The `Seed` attribute is the seed used for the underlying random sampler and does not need to match the image shown.
* **Action**: Set the rest of the properties according to the image below. That is, `Depth = 0, Layer Count = 2, Separation Distance = 0.5, Placement Area = (6,6)`.
Note that the `Seed` values do not need to match the image above.
There is one more important thing left to do, in order to make sure all the above Randomizers operate as expected. Since `BackgroundObjectPlacementRandomizer` spawns objects, it already knows which objects in the Scene it is dealing with; however, the rest of the Randomizers we added are not yet aware of what objects they should target because they don't spawn their own objects.
* **Action**: Add `MyLightRandomizer` to the list of Randomizers in `SimulationScenario`.
You will notice that the Randomizer's UI snippet contains one Parameter named `Light Intensity Parameter`. This is the same Parameter we added in the code block above. Here, you can set the sampling distribution (`Value`), `Seed`, and `Range` for this float Parameter:
You will notice that the Randomizer's UI snippet contains one Parameter named `Light Intensity Parameter`. This is the same Parameter we added in the code block above. Here, you can set the sampling distribution (`Value`) and `Range` for this float Parameter:
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<imgsrc="Images/light_rand_1.png"width="420"/>
If you now check the UI snippet for `MyLightRandomizer`, you will notice that `Color Parameter` is added. This Parameter includes four separate randomized values for `Red`, `Green`, `Blue` and `Alpha`. Note that the meaningful range for all of these values is 0-1 (and not 0-255). You can see that the sampling range for red, green, and blue is currently also set to 0-1, which means the parameter covers a full range of colors. A color with (0,0,0) RGB components essentially emits no light. So, let's increase the minimum a bit to avoid such a scenario.
* **Action**: Increase the minimum value for red, green, and blue components to 0.4 (this is an arbitrary number that typically produces good-looking results).
Each value should also already have a unique `Seed` specified. This is the seed which the sampler will use to produce a random value from the specified distribution. If two random parameters have the same seed, range, and distribution, they will always have the same value. In the case of this color, this would lead to the red, green, and blue components having equal values, and thus the produced color always being a shade of grey. As such, in order to get varied colors and not just grey, we need to make sure the seed values are different for our red, green, and blue components.
* **Action**: In the UI snippet for `MyLightRandomizer`, make sure the red, green, and blue components have different `Seed` values. Set the distribution and value for Alpha to `Constant` and 1, as we do not want to randomize the alpha component of the color.
The UI for `My Light Randomizer` should now look like this:
Steven Leal
4 年前