Custom Pass material nodes

DreamShader » Builtins » Custom Pass material nodes

Two material expressions of the DreamShaderPass module, reached from a .dss like any other expression, through UE.<Name>: one writes the data a mesh pass draws, the other lets an ordinary material read an exported buffer.

UE.DreamPassOutput

// M_HighlightMask.dss -- the override material of a mesh pass
#pragma material(ShadingModel = Unlit, bUsedWithSkeletalMesh = true, bUsedWithInstancedStaticMeshes = true)

export void M_HighlightMask(inout material m)
{
    m.EmissiveColor = float3(0, 0, 0);
    UE.DreamPassOutput(Output0 = float4(1, 0, 0, 0));
}

A statement, not a value: the material's custom output with four pins, Output0…Output3, which a mesh pass writes as write Output0 = <buffer>;. Each takes a float to float4 and writes a float4 — a float is replicated, a float2 or float3 padded with zeros. An unconnected pin writes 0.

• It is also what makes a material able to be drawn by a mesh pass: the node gives the material a shader tag, and the mesh pass's shaders are compiled only for tagged materials — so a project's other materials pay nothing for Custom Pass.
• An object's own material can carry it too. A mesh pass with Mode = Own draws each selected object with its own material, and reads that material's UE.DreamPassOutput — per-object data (wetness, an id, a mask) without an override.
• Top level only. The engine compiles custom outputs from the material's own graph, not from a material function's. Inside a function the node does nothing — no tag, no outputs — so DreamShader warns, and the material editor does not offer it there.
• One per material.
• It works the same with Substrate on: its inputs are plain values, not a BSDF.

UE.DreamPassBuffer

// M_Ground.dss -- a glow under the highlighted objects
export void M_Ground(inout material m)
{
    float Glow = UE.DreamPassBuffer(Pipeline = "CP_Highlight", Buffer = "Blurred").r;
    m.EmissiveColor = Glow * float3(1.0, 0.6, 0.0);
}

Samples an exported buffer's render target. float4.

• In a vertex shader (World Position Offset) it samples mip 0.
• A missing pipeline, a buffer the pipeline does not have or does not export, a built-in buffer, and an integer or depth buffer are errors — in DreamShader when the .dss compiles, and in the material editor.
• What it reads depends on when the buffer's last writer runs — this frame's picture or last frame's; see the table in Exported buffers.
• The material depends on the .dsp: changing the buffer's export recompiles it.
• The material editor's preview shows the render target's last contents.

Reading a pass's buffers in a pass material

A material run by a fullscreen pass reads the pass's buffers with the engine's own UE.UserSceneTexture(UserSceneTexture = "<name>", Coordinates = UV) node, whose name the pass binds with read <name> = <buffer>; — no Custom Pass node is involved, and the material previews as any post-process material does.

See also

• Custom Pass pipelines — .dsp
• Custom Pass runtime
• UE.Expression — how reflected expressions are called