These Custom HLSL nodes let you execute custom HLSL code during particle simulation. You can use an operator for horizontal flow or a block for vertical flow (in contexts).
Node settings Setting name UI Location Action Name Text field Inspector Choose the name of the block HLSL Code Button Graph node Opens a code editor window Available Function Drop down Graph node Pick which function to execute HLSL CodeThe HLSL code can be either embedded in the node or an HLSL file can be used. You can provide multiple functions in the same HLSL source (embedded or file), in this case, you'll have to pick the desired one in a choice list in the node.
To be valid and correctly interpreted by the VFX Graph, some conventions must be adopted.
To be properly recognized by VFX Graph the function must fulfill the following requirements:
You can specify a tooltip for each function parameter using the three slash comment notation as shown below:
/// <parameter-name>: the tooltip's text
These comments must be right above the function declaration.
/// a: the tooltip for parameter a
/// b: the tooltip for parameter b
float Distance(in float3 a, in float3 b)
{
return distance(a, b);
}
You may want to write a helper function that you don't want to be exposed in the node's choice list.
In that case, simply put this special comment above the function declaration:
/// Hidden
float SomeFunction(in float a)
{
...
}
When you need to implement helper functions, you must use a HLSL file, not the embedded HLSL code.
Supported types Basic types HLSL Type Port Type Description bool bool A scalar value represented as a boolean. uint uint A scalar value represented as an unsigned integer. int int A scalar value represented as a integer. float float A scalar value represented as a float. float2 Vector2 A structure containing two float. float3 Vector3 A structure containing three float. float4 Vector4 A structure containing four float. float4x4 Matrix4x4 A structure representing a matrix. VFXGradient Gradient A structure that describes a gradient that can be sampled. VFXCurve AnimationCurve A structure that describes a curve that can be sampled. Texture types HLSL Type Port Type Description VFXSampler2D Texture2D A structure containing a sampler state and a two-dimensional texture. VFXSampler3D Texture3D A structure containing a sampler state and a three-dimensional texture. VFXSampler2DArray Texture2DArray A structure containing a sampler state and an array of two-dimensional textures. VFXSamplerCube TextureCube A structure containing a sampler state and a cube texture. Buffers HLSL Type Port Type Description StructuredBuffer GraphicsBuffer A read-only buffer for storing an array of structures or basic HLSL data types. ByteAddressBuffer GraphicsBuffer A read-only raw buffer. Buffer GraphicsBuffer A read-only raw buffer for basic HLSL types. AppendStructuredBuffer GraphicsBuffer A read-only buffer where you can append new entries. ConsumeStructuredBuffer GraphicsBuffer A read-only buffer where you can remove entries. RWBuffer GraphicsBuffer A read-write raw buffer for basic HLSL types. RWStructuredBuffer GraphicsBuffer A read-write buffer for storing an array of structures or basic HLSL data types. RWByteAddressBuffer GraphicsBuffer A read-write raw buffer. Sampling TexturesThe simplest way to sample a texture is to use the VFX Graph structure called VFXSampler2D (or VFXSample3D) which is defined as shown below:
struct VFXSampler2D
{
Texture2D t;
SamplerState s;
};
VFX Graph provides this function: float4 SampleTexture(VFXSampler2D texure, float2 coordinates).
But you can also use HLSL built-in functions to sample a texture using the VFXSampler2D fields.
In that case, since this is used in a compute shader you must specify which mipmap level to sample (use SampleLevel for instance).
You can use two types of buffers: ByteAddressBuffer and StructuredBuffer<>. In both cases the usage is the same as in any HLSL code:
ByteAddressBuffer: use the Load functionuint char = buffer.Load(attributes.particleId % count);
StructuredBuffer<>: use classic index accessorfloat angle = phase + freq * buffer[attributes.particleId % bufferSize];
Gradients are handled specifically in VFX Graph (they are packed in a single texture) so you must use a dedicated function to sample them.
Here is the function definition: SampleGradient(VFXGradient gradient, float t)
float3 color = SampleGradient(grad, t);
Sampling a curve is really similar to sampling a gradient.
Here is the function definition: SampleCurve(VFXCurve curve, float t)
float r = SampleCurve(curve, t);
You can edit your HLSL code directly inside Unity Editor by clicking the Edit button on the node in the graph (see screenshot above).
The HLSL Code Editor supports the following shortcuts:
Ctrl + Z and Ctrl + Y for Undo/Redo (independent from the Unity Editor undo stack)Ctrl + S to save the current HLSL codeCtrl + Mouse Wheel to change the font sizeIf you need to write down the name of a particle attribute, you can drag&drop drop the attribute from the blackboard to the code editor. This way you avoid any risk of typo.
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