131 lines
5.1 KiB
Markdown
131 lines
5.1 KiB
Markdown
# Probability Sampling
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Menu Path : **Operator > Logic > Probability Sampling**
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The **Probability Sampling** Operator performs a kind of switch/case operation where a weight controls the probability of selecting a case. If all weights are equal, this Operator produces a uniform distribution of the different output values.
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## Operator settings
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| **Setting** | **Description** |
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| --------------------- | ------------------------------------------------------------ |
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| **Integrated Random** | (**Inspector**) Specifies whether this Operator generates the random number itself, or if it allows you to input a custom random number instead. |
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| **Seed** | Defines the scope of the random number. For more information, see [Random Number](Operator-RandomNumber.md#oprerator-settings).<br/>This setting only appears if you enable **Integrated Random**. |
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| **Constant** | Specifies whether the generated random number is constant or not. For more information, see [Random Number](Operator-RandomNumber.md#oprerator-settings).<br/>This setting only appears if you enable **Integrated Random**. |
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| **Entry Count** | The number of cases to test. The maximum value is **32**. |
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## Operator properties
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| **Input** | **Type** | **Description** |
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| ------------ | --------------------------------------- | ------------------------------------------------------------ |
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| **Weight 0** | float | The weight for the first value. The larger this value is compared to the rest of the weights, the higher the chance the Operator selects the first value. |
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| **Value 0** | [Configurable](#operator-configuration) | The value to output if the Operator selects **Weight 0**. |
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| **Weight 1** | float | The weight for the second value. The larger this value is compared to the rest of the weights, the higher the chance the Operator selects the second value. |
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| **Value 1** | [Configurable](#operator-configuration) | The value to output if the Operator selects **Weight 1**. |
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| **Weight N** | float | To expose more cases, increase the **Entry Count**. |
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| **Value N** | [Configurable](#operator-configuration) | To expose more cases, increase the **Entry Count**. |
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| **Rand** | float | The value this Operator uses to choose a value from amongst the weights. This should be between **0** and **1**.This property only appears if you disable **Integrated Random**. |
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| **Hash** | uint | The value this Operator uses to create a constant random value. This property only appears if you enable **Constant**. |
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| **Output** | **Type** | **Description** |
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| ---------- | --------------------------------------- | ------------------------------------------------------------ |
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| **Output** | [Configurable](#operator-configuration) | The value where the corresponding case entry is equal to **Input** value or, if there isn’t any match, **Default**. |
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## Operator configuration
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To view the Node's configuration, click the **cog** icon in the Node's header.
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| **Property** | **Description** |
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| ------------ | ------------------------------------------------------------ |
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| **Type** | The value type this Operator uses. For the list of types this property supports, see [Available types](#available-types). |
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### Available types
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You can use the following types for your **Input values** and **Output** ports:
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- **Bool**
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- **Int**
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- **Uint**
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- **Float**
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- **Vector2**
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- **Vector3**
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- **Vector4**
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- **Gradient**
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- **AnimationCurve**
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- **Matrix**
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- **OrientedBox**
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- **Color**
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- **Direction**
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- **Position**
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- **Vector**
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- **Transform**
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- **Circle**
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- **ArcCircle**
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- **Sphere**
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- **ArcSphere**
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- **AABox**
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- **Plane**
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- **Cylinder**
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- **Cone**
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- **ArcCone**
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- **Torus**
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- **ArcTorus**
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- **Line**
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- **Flipbook**
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- **Camera**
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This list does not include any type that corresponds to a buffer or texture because it is not possible to assign these types as local variables in generated HLSL code.
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## Details
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The internal algorithm of this Operator can be described by this sample code :
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```
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//Input
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float[] weight = { 0.2f, 1.2f, 0.7f };
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char[] values = { 'a', 'b', 'c' };
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//Compute prefix sum of height
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float[] prefixSumOfWeight = new float[height.Length];
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prefixSumOfHeight[0] = weight[0];
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for (int i = 1; i < weight.Length; ++i)
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prefixSumOfHeight[i] = weight[i] + weight[i - 1];
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//Pick a random value [0, sum of all height]
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var rand = Random.Range(0.0f, weight[weight.Length - 1]);
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//Evaluate probability sampling
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char r = 'z';
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for (int i = 0; i < weight.Length; ++i)
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{
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if (rand < prefixSumOfWeight[i] || i == weight.Length - 1)
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{
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r = values[i];
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break;
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}
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}
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//Output
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Debug.Log("Result : " + r.ToString());
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```
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