Pipelines

A pipeline is a combination of one or multiple draw::Pass along with some internal logic for rendering. The pass types an object can subscribe to is listed by eMaterialPipeline. The objects subscribe to the draw::Pass with its associated shaders.

A single object can subscribe to multiple pipelines. A renderable object type is called a geometry type and listed in eMaterialGeometry.

Pipelines are filled with scene data and are view agnostic. Multiple views can call the same pipeline (e.g. the 6 views of a cubemap). View dependant resources should be stored inside views and passed to the render() method of the pipelines (e.g. ShadingView::rt_buffer_opaque_).

Material Pipeline

A core design principle of EEVEE is that all pipelines should be compatible with all geometry type (with a few exceptions).

flowchart TD
    A[Mesh]
    B[Curves]
    D[Point Cloud]
    C[Volume]
    E[World]

    classDef geometry stroke:#f66
    class A,B,C,D,E geometry;

    I[Deferred]
    J[Forward]
    K[Shadow]
    L[Volume]
    M[Background]
    N[World]

    classDef pipeline stroke:#66f
    class I,J,K,L,M,N pipeline;

    E --> L & M & N
    C --> L
    A & B & D --> Reroute{Solid} --> I & J & K & L

    S[Prepass]
    T[Gbuffer]
    U[Prepass]
    V[Shading]
    W[Occupancy]
    X[Material]
    Y[Shadow]
    Z[World]

    classDef shader stroke:#6f6
    class S,T,U,V,W,X,Y,Z shader;

    I --> S & T
    J --> U & V
    K --> Y
    L --> W & X
    M & N --> Z

Red is geometry type, blue is pipeline type, green is shader pass type.

Internally, the pass type maps to a fragment shader and the geometry type to a vertex shader. Some geometry type still need some special code in the fragment stage, and vice-versa, some pipelines need adjustments of the vertex shader. For this reasons, the MAT_GEOM_* (for geometry types) and MAT_* (for pipeline types) exists.