triga-budapest

Graphics work in the same language, with the same types, as everything else here. This is the box-geometry module of the scene behind the rendered frames on the home page.

Source: examples/triga-budapest

src/box_geom.fab#

One file of a multi-file package: it refers to siblings that are not shown here.

importa ex "triga:math" privata math

# ---------------------------------------------------------------------------
# Lit box geometry — 24 vertices (4 per face × 6 faces), 36 indices.
#
# Each face has its own 4 vertices so normals are flat per-face.
# Vertex stride: 9 f32 (36 bytes) = position(3) + normal(3) + color(3).
#
# Face order: +X, -X, +Y, -Y, +Z, -Z
# ---------------------------------------------------------------------------

@ privata
functio _append_face(
    lista<f32> payload,
    f32 x1, f32 y1, f32 z1,
    f32 x2, f32 y2, f32 z2,
    f32 x3, f32 y3, f32 z3,
    f32 x4, f32 y4, f32 z4,
    f32 nx, f32 ny, f32 nz,
    f32 r, f32 g, f32 b
) → lista<f32> {
    payload.appende(x1)
    payload.appende(y1)
    payload.appende(z1)
    payload.appende(nx)
    payload.appende(ny)
    payload.appende(nz)
    payload.appende(r)
    payload.appende(g)
    payload.appende(b)

    payload.appende(x2)
    payload.appende(y2)
    payload.appende(z2)
    payload.appende(nx)
    payload.appende(ny)
    payload.appende(nz)
    payload.appende(r)
    payload.appende(g)
    payload.appende(b)

    payload.appende(x3)
    payload.appende(y3)
    payload.appende(z3)
    payload.appende(nx)
    payload.appende(ny)
    payload.appende(nz)
    payload.appende(r)
    payload.appende(g)
    payload.appende(b)

    payload.appende(x4)
    payload.appende(y4)
    payload.appende(z4)
    payload.appende(nx)
    payload.appende(ny)
    payload.appende(nz)
    payload.appende(r)
    payload.appende(g)
    payload.appende(b)

    redde payload
}

# ---------------------------------------------------------------------------
# box_indices — 36 indices for 24 lit box vertices.
# ---------------------------------------------------------------------------
functio box_indices() → lista<u32> {
    varia lista<u32> idx ← vacua
    varia numerus face ← 0
    dum face < 6 {
        fixum u32 base ← ((face * 4) ↦ u32)
        idx.appende(base)
        idx.appende(base + 1)
        idx.appende(base + 2)
        idx.appende(base)
        idx.appende(base + 2)
        idx.appende(base + 3)
        face ← face + 1
    }
    redde idx
}

# ---------------------------------------------------------------------------
# box_vertex_payload — interleaved [px,py,pz, nx,ny,nz, cr,cg,cb, …]
# for 24 lit vertices.  This is the only payload the host needs.
# ---------------------------------------------------------------------------
functio box_vertex_payload(de math.Box3 bounds, f32 r, f32 g, f32 b) → lista<f32> ∪ nihil {
    si bounds.validum() ≡ falsum ergo redde nihil

    fixum f32 x1 ← bounds.min.x
    fixum f32 y1 ← bounds.min.y
    fixum f32 z1 ← bounds.min.z
    fixum f32 x2 ← bounds.max.x
    fixum f32 y2 ← bounds.max.y
    fixum f32 z2 ← bounds.max.z

    varia lista<f32> p ← vacua

    # +X face (right) — normal (1,0,0)
    p ← _append_face(p, x2, y1, z1, x2, y2, z1, x2, y2, z2, x2, y1, z2, 1.0, 0.0, 0.0, r, g, b)

    # -X face (left) — normal (-1,0,0)
    p ← _append_face(p, x1, y1, z2, x1, y2, z2, x1, y2, z1, x1, y1, z1, -1.0, 0.0, 0.0, r, g, b)

    # +Y face (top) — normal (0,1,0)
    p ← _append_face(p, x1, y2, z1, x2, y2, z1, x2, y2, z2, x1, y2, z2, 0.0, 1.0, 0.0, r, g, b)

    # -Y face (bottom) — normal (0,-1,0)
    p ← _append_face(p, x1, y1, z2, x2, y1, z2, x2, y1, z1, x1, y1, z1, 0.0, -1.0, 0.0, r, g, b)

    # +Z face (front/pest) — normal (0,0,1)
    p ← _append_face(p, x1, y1, z2, x2, y1, z2, x2, y2, z2, x1, y2, z2, 0.0, 0.0, 1.0, r, g, b)

    # -Z face (back/buda) — normal (0,0,-1)
    p ← _append_face(p, x2, y1, z1, x1, y1, z1, x1, y2, z1, x2, y2, z1, 0.0, 0.0, -1.0, r, g, b)

    redde p
}

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