Custom Gradient for Jobs

2025-04-04 08:26 UTC o3-mini-high Open in ChatGPT ↗

You

I want to make a custom unity object type that looks and works like the Gradient class, but it’s compatible and optimal for Job system, native containers, burst etc

ChatGPT

To build a gradient-like type that works in Burst-compiled jobs and with native containers, you need to design your data structure so that all of its data is unmanaged and stored in memory allocated with Unity’s native allocators (or, even better, in a BlobAsset if the data is immutable). Unlike the built-in Gradient class—which is managed and not Burst-friendly—you must implement your own struct with only blittable types.

Below are some key points and an example approach:

---

Key Considerations

• Unmanaged Data:
  Your custom gradient must use only unmanaged types (e.g., structs with primitive fields or math types from Unity.Mathematics). This means avoiding any managed references.

• Native Containers / BlobAssets:
  If the gradient data is static (or changes rarely), consider using a BlobAsset. BlobAssets are allocated once and can be read in jobs without overhead. If the gradient is dynamic, use a NativeArray (or similar container) with an appropriate Allocator (e.g., Allocator.TempJob or Allocator.Persistent) and remember to dispose of it when done.

• Interpolation Logic:
  Implement your own evaluation function (similar to Gradient.Evaluate) that finds the correct keys and interpolates between them. You can use math.lerp and math.unlerp from Unity.Mathematics for Burst-friendly linear interpolation.

• Memory Management:
  When using NativeArrays, ensure you properly dispose of them to prevent memory leaks.

• Burst Compatibility:
  Structure your code so that all operations within a job are burst-compatible. This means no managed memory allocation or calls to non-Burst-compiled functions.

---

Example Implementation

Below is a simplified example of a Burst-friendly gradient using a NativeArray of gradient keys. (In a real-world scenario, you might want to separate color and alpha keys or support additional interpolation modes.)

using Unity.Burst;
using Unity.Collections;
using Unity.Mathematics;
using UnityEngine;

// A simple struct representing a gradient key.
public struct GradientKey
{
    public float time;      // Time value between 0 and 1.
    public float4 color;    // Color stored as float4 (RGBA).

    public GradientKey(float time, float4 color)
    {
        this.time = time;
        this.color = color;
    }
}

// A custom gradient type using a NativeArray to store gradient keys.
public struct NativeGradient
{
    public NativeArray<GradientKey> keys;

    public NativeGradient(NativeArray<GradientKey> keys)
    {
        this.keys = keys;
    }

    // Evaluates the gradient at the given time (0 to 1) using linear interpolation.
    public float4 Evaluate(float time)
    {
        // Clamp time to the valid range.
        time = math.clamp(time, 0f, 1f);
        int count = keys.Length;
        if (count == 0)
            return new float4(0f, 0f, 0f, 0f);
        if (count == 1)
            return keys[0].color;

        GradientKey prev = keys[0];
        for (int i = 1; i < count; i++)
        {
            GradientKey next = keys[i];
            if (time <= next.time)
            {
                // Calculate normalized t between the two keys.
                float t = math.unlerp(prev.time, next.time, time);
                return math.lerp(prev.color, next.color, t);
            }
            prev = next;
        }
        return keys[count - 1].color;
    }
}

How to Use It

1. Allocation:
   Allocate your NativeArray with an appropriate Allocator. For example, if you’re setting up a gradient for a job:

   NativeArray<GradientKey> gradientKeys = new NativeArray<GradientKey>(/* number of keys */, Allocator.TempJob);
   // Fill gradientKeys with your data.
   NativeGradient myGradient = new NativeGradient(gradientKeys);

2. Job Integration:
   You can pass NativeGradient to your job if it’s marked with [BurstCompile]. Since it only contains unmanaged data, it will be compatible.

3. Disposal:
   Once you’re done using the gradient, dispose of the NativeArray to free memory:

   gradientKeys.Dispose();

4. BlobAsset Option:
   For immutable gradient data, consider building a BlobAsset that contains your keys. BlobAssets are even more efficient for read-only data in jobs. You would use a BlobBuilder to construct a BlobAssetReference that your jobs can then read from.

---

Final Thoughts

By creating a custom struct that holds your gradient keys in native memory and implementing your own evaluation function, you can mimic the functionality of the built-in Gradient class in a way that is fully compatible with the Job system, native containers, and Burst compilation. This approach gives you both the performance benefits of Burst and the flexibility of custom gradient logic.

Feel free to expand this example based on your project needs (for example, by adding support for more complex interpolation or handling separate alpha keys).

You

ok, it needs to be editable in the editor as well, like the normal Gradient class

ChatGPT

To achieve an editor-editable gradient while still having a Burst-friendly runtime representation, you can separate your data into two parts:

1. Editor-Editable Data:
   Create a serializable asset (or a MonoBehaviour) that lets you edit the gradient keys in the Unity Editor. This asset can use managed types (like a List of a serializable key struct) and even a custom property drawer/editor to mimic the visual interface of Unity’s built-in Gradient.

2. Runtime Native Data:
   When your game starts (or when you need to schedule a job), convert the editor-managed data into an unmanaged, native container (or even a BlobAsset) that your jobs can safely use with Burst.

Below is an example implementation:

---

Step 1: Define a Serializable Gradient Key

Create a serializable struct that represents a gradient key for editor editing. You can use Unity’s Color type for ease of use in the editor.

using UnityEngine;

[System.Serializable]
public struct GradientKeyData
{
    [Range(0f, 1f)]
    public float time;
    public Color color;
}

---

Step 2: Create a ScriptableObject for Editing

This asset holds the list of gradient keys. You can create a custom inspector later if you want a preview or more advanced editing tools.

using System.Collections.Generic;
using UnityEngine;

[CreateAssetMenu(menuName = "Custom/Editable Gradient")]
public class EditableGradientAsset : ScriptableObject
{
    public List<GradientKeyData> keys = new List<GradientKeyData>();

    // Optionally, you could add methods to validate or sort keys here.
}

---

Step 3: Define the Native (Burst-Friendly) Structures

Create a native representation using only unmanaged, blittable types. In this example, we’ll convert Color to a float4 (from Unity.Mathematics).

using Unity.Mathematics;
using UnityEngine;

public struct NativeGradientKey
{
    public float time;
    public float4 color;

    public NativeGradientKey(float time, Color color)
    {
        this.time = time;
        this.color = new float4(color.r, color.g, color.b, color.a);
    }
}

Now define a native gradient structure that stores the keys in a NativeArray and provides an evaluation function:

using Unity.Burst;
using Unity.Collections;
using Unity.Mathematics;

public struct NativeGradient
{
    public NativeArray<NativeGradientKey> keys;

    public NativeGradient(NativeArray<NativeGradientKey> keys)
    {
        this.keys = keys;
    }

    // Evaluates the gradient at a given time (0 to 1) using linear interpolation.
    [BurstCompile]
    public float4 Evaluate(float time)
    {
        time = math.clamp(time, 0f, 1f);
        int count = keys.Length;
        if (count == 0)
            return new float4(0f, 0f, 0f, 0f);
        if (count == 1)
            return keys[0].color;

        NativeGradientKey prev = keys[0];
        for (int i = 1; i < count; i++)
        {
            NativeGradientKey next = keys[i];
            if (time <= next.time)
            {
                float t = math.unlerp(prev.time, next.time, time);
                return math.lerp(prev.color, next.color, t);
            }
            prev = next;
        }
        return keys[count - 1].color;
    }
}

---

Step 4: Converting the Editable Data to a NativeGradient

At runtime (for example, in a MonoBehaviour’s Awake or just before scheduling a job), convert the editable asset’s keys into a native container.

using Unity.Collections;
using UnityEngine;
using Unity.Mathematics;

public class GradientRuntimeLoader : MonoBehaviour
{
    // Reference your ScriptableObject in the inspector.
    public EditableGradientAsset editableGradient;

    // This will be your runtime, Burst-friendly gradient.
    public NativeGradient nativeGradient;

    void Start()
    {
        // Allocate a NativeArray with the correct number of elements.
        NativeArray<NativeGradientKey> nativeKeys = new NativeArray<NativeGradientKey>(
            editableGradient.keys.Count, Allocator.Persistent);

        // Convert each key.
        for (int i = 0; i < editableGradient.keys.Count; i++)
        {
            GradientKeyData keyData = editableGradient.keys[i];
            nativeKeys[i] = new NativeGradientKey(keyData.time, keyData.color);
        }

        nativeGradient = new NativeGradient(nativeKeys);
    }

    void OnDestroy()
    {
        if (nativeGradient.keys.IsCreated)
            nativeGradient.keys.Dispose();
    }
}

---

Final Notes

• Editor Customization:
  If you want the editor interface to mimic Unity’s built-in Gradient field, you can create a custom editor or property drawer for your EditableGradientAsset. This might involve drawing a preview texture and custom sliders.

• Runtime Conversion:
  The conversion from editable (managed) data to native data is typically done once at startup or whenever the gradient data changes. For static or rarely changing gradients, consider using a BlobAsset for further efficiency.

• Memory Management:
  Always ensure that any allocated NativeArray or BlobAsset is properly disposed of when it’s no longer needed to prevent memory leaks.

By following this two-tier approach, you maintain the convenience of editing your gradient in the Editor while still benefiting from Burst and the Job system at runtime.

You

I need the Editable version and the actual data to be one object. i cant ask my users to manage 2 things

ChatGPT

You can merge both the editable and runtime (native) representations into a single asset by making a ScriptableObject that holds the serialized editable data and, at runtime, builds its own native (or blob) version for Burst/jobbing. This way your users only manage one object, and you do the conversion behind the scenes.

Below is one approach:

---

1. Define a Serializable Gradient Key

This struct will be editable in the inspector.

using UnityEngine;

[System.Serializable]
public struct GradientKeyData
{
    [Range(0f, 1f)]
    public float time;
    public Color color;
}

---

2. Create the Burst-Friendly Native Structures

These types use only unmanaged data so they’re safe for Burst. The native key converts the editor’s Color into a float4 from Unity.Mathematics, and the native gradient offers an evaluation method.

using Unity.Mathematics;
using Unity.Burst;
using Unity.Collections;

public struct NativeGradientKey
{
    public float time;
    public float4 color;

    public NativeGradientKey(float time, UnityEngine.Color color)
    {
        this.time = time;
        this.color = new float4(color.r, color.g, color.b, color.a);
    }
}

public struct NativeGradient
{
    public NativeArray<NativeGradientKey> keys;

    public NativeGradient(NativeArray<NativeGradientKey> keys)
    {
        this.keys = keys;
    }

    // Evaluates the gradient at a given time (0 to 1) using linear interpolation.
    [BurstCompile]
    public float4 Evaluate(float time)
    {
        time = math.clamp(time, 0f, 1f);
        int count = keys.Length;
        if (count == 0)
            return new float4(0f, 0f, 0f, 0f);
        if (count == 1)
            return keys[0].color;

        NativeGradientKey prev = keys[0];
        for (int i = 1; i < count; i++)
        {
            NativeGradientKey next = keys[i];
            if (time <= next.time)
            {
                float t = math.unlerp(prev.time, next.time, time);
                return math.lerp(prev.color, next.color, t);
            }
            prev = next;
        }
        return keys[count - 1].color;
    }
}

---

3. Combine Them in a Single ScriptableObject

This asset holds the list of keys for editor editing and automatically converts the data to a native container at runtime. It also takes care of disposing the native container when the asset is unloaded.

using System.Collections.Generic;
using UnityEngine;
using Unity.Collections;
using Unity.Mathematics;

[CreateAssetMenu(menuName = "Custom/Editable Native Gradient")]
public class EditableNativeGradient : ScriptableObject
{
    // Editable gradient keys for the inspector.
    [SerializeField]
    private List<GradientKeyData> keys = new List<GradientKeyData>();

    // This field is not serialized; it is built at runtime.
    private NativeGradient nativeGradient;
    private bool nativeInitialized = false;

    /// <summary>
    /// Converts the editable keys to a Burst-friendly NativeGradient.
    /// </summary>
    private void InitializeNativeGradient()
    {
        if (nativeInitialized)
            return;

        // Create a NativeArray from the serialized keys.
        NativeArray<NativeGradientKey> nativeKeys = new NativeArray<NativeGradientKey>(
            keys.Count, Allocator.Persistent);

        for (int i = 0; i < keys.Count; i++)
        {
            GradientKeyData keyData = keys[i];
            nativeKeys[i] = new NativeGradientKey(keyData.time, keyData.color);
        }

        nativeGradient = new NativeGradient(nativeKeys);
        nativeInitialized = true;
    }

    /// <summary>
    /// Returns the Burst-friendly native gradient, initializing it if necessary.
    /// </summary>
    public NativeGradient GetNativeGradient()
    {
        if (!nativeInitialized)
            InitializeNativeGradient();
        return nativeGradient;
    }

    /// <summary>
    /// Disposes of the native gradient to free native memory.
    /// </summary>
    public void DisposeNativeGradient()
    {
        if (nativeInitialized && nativeGradient.keys.IsCreated)
        {
            nativeGradient.keys.Dispose();
            nativeInitialized = false;
        }
    }

    // When the asset is enabled (e.g., entering play mode) we can initialize the native version.
    private void OnEnable()
    {
        // Optionally initialize immediately, or wait until GetNativeGradient() is called.
        if (Application.isPlaying)
            InitializeNativeGradient();
    }

    // Clean up the native container when the asset is disabled or unloaded.
    private void OnDisable()
    {
        DisposeNativeGradient();
    }

#if UNITY_EDITOR
    // In the editor, if keys are modified, refresh the native gradient in play mode.
    private void OnValidate()
    {
        if (Application.isPlaying)
        {
            DisposeNativeGradient();
            InitializeNativeGradient();
        }
    }
#endif
}

---

How This Works

• Editor & Runtime in One:
  The EditableNativeGradient asset holds a serializable list of gradient keys for editing in the inspector. When the game starts (or whenever you need the native version), the asset converts these keys into a native container.

• Single Object for Users:
  Your users only need to manage a single asset. They edit the gradient in the inspector as they would with a normal Gradient, and the conversion to a Burst-friendly native format happens automatically.

• Usage in Jobs:
  In your job code, you can call GetNativeGradient() on the asset to retrieve the Burst-compatible data. Just be sure to call it before scheduling your job so that the native data is ready.

• Memory Management:
  The native container is allocated with a Persistent allocator and is disposed of in OnDisable so that you won’t run into memory leaks.

---

Final Thoughts

This unified approach encapsulates both the editor-editable data and the runtime native representation in one object. It hides the complexity of conversion from your users while still giving you the performance benefits of Burst, Native Containers, and the Job System at runtime.

You

What if we extend Unity’s gradient class instead of making a completely new thing?

ChatGPT

Unity’s built-in Gradient is a sealed, managed class, so you can’t extend it directly. Even if it were extendable, its internal representation isn’t designed for use in Burst-compiled jobs or native containers. Instead, you have two common approaches:

1. Wrapper Approach:
   Create a custom ScriptableObject (or another asset) that holds a Unity Gradient for editor editing. At runtime, extract the key data (via the Gradient’s colorKeys and alphaKeys) and build a native, Burst-friendly representation (using a NativeArray or a BlobAsset). This way, your users only manage one asset while you perform the conversion behind the scenes.

2. Custom Implementation:
   Build a completely new gradient type that is both editor-editable and Burst-compatible by combining a serializable list of keys with logic that converts that data to a native format at runtime. This was demonstrated in the previous examples.

The wrapper approach leverages the familiar Gradient UI in the inspector while still providing the performance benefits at runtime. However, you must still perform the conversion process because the built-in Gradient isn’t structured with native, unmanaged memory in mind.

Here’s a brief example using the wrapper approach:

using UnityEngine;
using Unity.Collections;
using Unity.Mathematics;
using Unity.Burst;

[CreateAssetMenu(menuName = "Custom/Editable Wrapped Gradient")]
public class EditableWrappedGradient : ScriptableObject
{
    // Use Unity's Gradient for editor editing.
    public Gradient gradient = new Gradient();

    // Native representation for Burst jobs.
    private NativeArray<NativeGradientKey> nativeKeys;
    private bool nativeInitialized = false;

    // Convert Unity's Gradient keys to a native format.
    private void InitializeNativeGradient()
    {
        if (nativeInitialized) return;

        // Get the color keys from the built-in gradient.
        GradientColorKey[] colorKeys = gradient.colorKeys;
        nativeKeys = new NativeArray<NativeGradientKey>(colorKeys.Length, Allocator.Persistent);

        for (int i = 0; i < colorKeys.Length; i++)
        {
            GradientColorKey key = colorKeys[i];
            nativeKeys[i] = new NativeGradientKey(key.time, key.color);
        }

        nativeInitialized = true;
    }

    // Retrieve the Burst-friendly native gradient.
    public NativeGradient GetNativeGradient()
    {
        if (!nativeInitialized)
            InitializeNativeGradient();
        return new NativeGradient(nativeKeys);
    }

    // Dispose of native memory when no longer needed.
    private void OnDisable()
    {
        if (nativeInitialized && nativeKeys.IsCreated)
        {
            nativeKeys.Dispose();
            nativeInitialized = false;
        }
    }
}

public struct NativeGradientKey
{
    public float time;
    public float4 color;

    public NativeGradientKey(float time, Color color)
    {
        this.time = time;
        this.color = new float4(color.r, color.g, color.b, color.a);
    }
}

public struct NativeGradient
{
    public NativeArray<NativeGradientKey> keys;

    public NativeGradient(NativeArray<NativeGradientKey> keys)
    {
        this.keys = keys;
    }

    // Evaluates the gradient at a given time (0 to 1) using linear interpolation.
    [BurstCompile]
    public float4 Evaluate(float time)
    {
        time = math.clamp(time, 0f, 1f);
        int count = keys.Length;
        if (count == 0)
            return new float4(0f, 0f, 0f, 0f);
        if (count == 1)
            return keys[0].color;

        NativeGradientKey prev = keys[0];
        for (int i = 1; i < count; i++)
        {
            NativeGradientKey next = keys[i];
            if (time <= next.time)
            {
                float t = math.unlerp(prev.time, next.time, time);
                return math.lerp(prev.color, next.color, t);
            }
            prev = next;
        }
        return keys[count - 1].color;
    }
}

Summary

• Direct Extension: You can’t extend Unity’s Gradient because it’s sealed and uses managed types not suited for jobs.
• Wrapper Pattern: Use a wrapper that exposes a Gradient for editing and builds a native version for runtime.
• Custom Asset: Alternatively, build a custom gradient type that is both editor-friendly and Burst-compatible by handling both representations within a single asset.

This lets you offer a seamless, single-object solution to your users while maintaining Burst and Job system compatibility at runtime.

You

Great. One more thing. whenever the gradient is changed in any way, the underlying data must be updated

ChatGPT

You can ensure that any changes to the gradient automatically update the underlying native data by overriding Unity’s OnValidate() method in your ScriptableObject. In OnValidate, you dispose of the old native container (if it exists) and rebuild it using the new gradient values. This way, every time the user tweaks the gradient in the editor, the runtime (native) representation is refreshed.

Below is an updated version of the previous wrapper approach with an OnValidate implementation:

using UnityEngine;
using Unity.Collections;
using Unity.Mathematics;
using Unity.Burst;

[CreateAssetMenu(menuName = "Custom/Editable Wrapped Gradient")]
public class EditableWrappedGradient : ScriptableObject
{
    // Use Unity's Gradient for editor editing.
    public Gradient gradient = new Gradient();

    // Native representation for Burst jobs.
    private NativeArray<NativeGradientKey> nativeKeys;
    private bool nativeInitialized = false;

    /// <summary>
    /// Convert Unity's Gradient keys to a native format.
    /// </summary>
    private void InitializeNativeGradient()
    {
        if (nativeInitialized)
            return;

        // Use the color keys from the built-in gradient.
        GradientColorKey[] colorKeys = gradient.colorKeys;
        nativeKeys = new NativeArray<NativeGradientKey>(colorKeys.Length, Allocator.Persistent);

        for (int i = 0; i < colorKeys.Length; i++)
        {
            GradientColorKey key = colorKeys[i];
            nativeKeys[i] = new NativeGradientKey(key.time, key.color);
        }

        nativeInitialized = true;
    }

    /// <summary>
    /// Retrieve the Burst-friendly native gradient.
    /// </summary>
    public NativeGradient GetNativeGradient()
    {
        if (!nativeInitialized)
            InitializeNativeGradient();
        return new NativeGradient(nativeKeys);
    }

    /// <summary>
    /// Dispose of native memory when no longer needed.
    /// </summary>
    private void DisposeNativeGradient()
    {
        if (nativeInitialized && nativeKeys.IsCreated)
        {
            nativeKeys.Dispose();
            nativeInitialized = false;
        }
    }

    private void OnEnable()
    {
        // In play mode, initialize immediately.
        if (Application.isPlaying)
            InitializeNativeGradient();
    }

    private void OnDisable()
    {
        DisposeNativeGradient();
    }

#if UNITY_EDITOR
    // This method is called whenever a property is changed in the editor.
    private void OnValidate()
    {
        // If in play mode, update the native data.
        if (Application.isPlaying)
        {
            DisposeNativeGradient();
            InitializeNativeGradient();
        }
    }
#endif
}

// Burst-friendly native key.
public struct NativeGradientKey
{
    public float time;
    public float4 color;

    public NativeGradientKey(float time, Color color)
    {
        this.time = time;
        this.color = new float4(color.r, color.g, color.b, color.a);
    }
}

// Burst-friendly native gradient with evaluation.
public struct NativeGradient
{
    public NativeArray<NativeGradientKey> keys;

    public NativeGradient(NativeArray<NativeGradientKey> keys)
    {
        this.keys = keys;
    }

    [BurstCompile]
    public float4 Evaluate(float time)
    {
        time = math.clamp(time, 0f, 1f);
        int count = keys.Length;
        if (count == 0)
            return new float4(0f, 0f, 0f, 0f);
        if (count == 1)
            return keys[0].color;

        NativeGradientKey prev = keys[0];
        for (int i = 1; i < count; i++)
        {
            NativeGradientKey next = keys[i];
            if (time <= next.time)
            {
                float t = math.unlerp(prev.time, next.time, time);
                return math.lerp(prev.color, next.color, t);
            }
            prev = next;
        }
        return keys[count - 1].color;
    }
}

How It Works

• OnValidate:
  Whenever the user changes the gradient in the editor, OnValidate is triggered. In play mode, it disposes of the current native data and reinitializes it based on the new gradient values.

• Unified Asset:
  Users only need to manage one asset—the ScriptableObject—while the conversion to a native format happens automatically behind the scenes.

• Runtime Safety:
  Native memory is allocated with a Persistent allocator and properly disposed in OnDisable (or when reinitializing in OnValidate) to avoid memory leaks.

This approach guarantees that the underlying Burst-friendly native data is always up to date with any changes made to the editable Gradient in the Unity Editor.

You

explain thoroughly how this interpolation works and why you use a loop

 NativeGradientKey prev = keys[0];
    for (int i = 1; i < count; i++)
    {
        NativeGradientKey next = keys[i];
        if (time <= next.time)
        {
            float t = math.unlerp(prev.time, next.time, time);
            return math.lerp(prev.color, next.color, t);
        }
        prev = next;
    }
    return keys[count - 1].color;

ChatGPT

This interpolation is a common way to perform piecewise linear interpolation between a set of keyframes (or gradient keys) that are sorted by time. Let’s break down each part of the code:

---

How the Interpolation Works

1. Initialization with the First Key:

   NativeGradientKey prev = keys[0];

   • The algorithm starts by taking the first key as the initial “previous” key.
   • The assumption is that the keys are sorted in ascending order based on their time values (from 0 to 1).

2. Iterating Over the Keys:

   for (int i = 1; i < count; i++)
   {
       NativeGradientKey next = keys[i];
       // ...
       prev = next;
   }

   • The loop begins at the second key (index 1) and goes through all the keys.
   • In each iteration, the current key (keys[i]) is treated as the “next” key.
   • At the end of each iteration, prev is updated to the current key for the next comparison.
   • This loop is essential because it allows the code to work with any number of keys, dynamically finding the right interval for interpolation.

3. Finding the Correct Interval:

   if (time <= next.time)
   {
       float t = math.unlerp(prev.time, next.time, time);
       return math.lerp(prev.color, next.color, t);
   }

   • The check if (time <= next.time) determines if the desired time falls between the current interval defined by prev and next.

   • Example:
     If prev.time is 0.2 and next.time is 0.5, and if the input time is 0.35, then the condition is met because 0.35 is less than or equal to 0.5.

   • Using math.unlerp:
     This function calculates a normalized interpolation factor t between prev.time and next.time. Essentially, it computes:

     t = (time - prev.time) / (next.time - prev.time)

     This value t is between 0 and 1, representing how far along the interval the given time is.

   • Using math.lerp:
     With the normalized factor t, math.lerp interpolates between the two colors:

     result = prev.color + t * (next.color - prev.color)

     This produces a smoothly interpolated color between the previous and next keys.

4. Handling Times Beyond the Last Key:

   return keys[count - 1].color;

   • If the loop completes without finding an interval (meaning the given time is greater than all the key times), the function returns the color of the last key.
   • This ensures that if time exceeds the range of the gradient, the gradient “holds” the final color.

---

Why Use a Loop?

• Flexibility:
  The number of keys can vary. A loop lets you handle any number of keys—whether it’s 2 keys (a simple start and end) or many keys for a more complex gradient.

• Dynamic Interval Detection:
  The loop sequentially checks each interval to determine where the input time falls. This is necessary because you don’t know ahead of time between which two keys the time will lie.

• Efficiency:
  Since the keys are sorted, a simple loop is sufficient to find the correct interval. For many cases, the number of keys is small, so the loop is very efficient. (For very large arrays of keys, more advanced search methods might be considered, but gradients typically have few keys.)

---

Visual Summary

Imagine a gradient as a number line from 0 to 1 with several points (keys) along it:

0     0.2         0.5         0.8       1
|------|-----------|-----------|---------|
 C0     C1          C2          C3        C4

• For a given time (say, 0.35), the loop will:
  • Start with prev = C0.
  • Check C1 at 0.2 (0.35 > 0.2, so continue).
  • Next, check C2 at 0.5 (0.35 <= 0.5, so it falls between C1 and C2).
  • Calculate t between 0.2 and 0.5.
  • Interpolate between the colors C1 and C2 using t.

This ensures that no matter how many keys there are or where the time value falls, the correct interval is used for interpolation.

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This approach provides smooth, linear transitions between colors in the gradient and allows you to dynamically support any number of keyframes in your gradient object.