Gradient Nodes

[Kink3d]

Gradient Nodes

Description

This PR adds gradient functionality via two new nodes. Sample Gradient node samples a gradient given a Time parameter. This gradient can be defined on the Gradient slot control view. The Gradient Asset node defines a gradient that can be sampled by multiple Sample Gradient nodes using different Time parameters.

These nodes support all functionality of the C# gradient type, including 2-8 color keys, 2-8 alpha keys and a mode value (Blend or Fixed). Internally to the shader each gradient is defined as a struct, wherein its variables are hardcoded in the case of the final shader, or assigned to multiple shader properties in the preview shader, to facilitate editing gradients without recompilation.

Details

New Nodes

• Gradient Asset
• Sample Gradient

New Features

• Gradient Material Slot
• Gradient Input Material Slot (and Control)
• Gradient Control
• Gradient Shader Property
• Gradient Slot Type (and concrete)
• Gradient Property type
• Gradient Slot Value
• Add Gradient Type to Subgraph and CodeFunctionNode
• Add Gradient Function to Functions.hlsl

Risk

• Changed GetPreviewProperty to GetPreviewProperties. Now takes a list of PreviewProperty with ref keyword to collect properties. This adds support for multiple preview properties from a single slot. This is needed for Gradient type.

[keijiro]

• I think you don't have to use ref in GetPreviewProperties. List<T> is a reference type, so you can modify the content without ref.
• If we know that there are only up to eight keys in gradients, we can easily unroll the for-loops in Unity_SampleGradient. I think it can be implemented without dynamic branching (no ifs and fors).

[Kink3d]

@keijiro Changes made, thanks :)

[keijiro]

@Kink3d It looks good to me. Although I have some ideas to try for further micro-optimization (e.g. step() is discouraged to use in GCN-based GPUs), I think this is good enough for an initial implementation.

[pbbastian]

"Gradient Asset" should just be "Gradient" as it doesn't actually represent an asset.

[pbbastian]

Getting these warnings:

Assets/ScriptableRenderPipeline/ShaderGraph/com.unity.shadergraph/Editor/Drawing/Controls/GradientControl.cs(48,28): warning CS0414: The private field `UnityEditor.ShaderGraph.Drawing.Controls.GradientControlView.m_SerializedProperty' is assigned but its value is never used

Assets/ScriptableRenderPipeline/ShaderGraph/com.unity.shadergraph/Editor/Drawing/Views/Slots/GradientSlotControlView.cs(24,28): warning CS0414: The private field `UnityEditor.ShaderGraph.Drawing.Slots.GradientSlotControlView.m_SerializedProperty' is assigned but its value is never used

[Kink3d]

@pbbastian fixed