Mesh Primitives

App: apps/mesh_primitives/

Demonstrates the MeshGen procedural mesh factories (engine PLM-244 / ADR 0082), part of Block SPL (splines / geometry / scatter). One of each primitive — box, cylinder, cone, plane, grid — is laid out in a row, with a sine-wave heightmap terrain behind them. Everything is built by the device-free modules/geometry core and drawn immediate-mode with a lit N·L shader, so the shapes’ generated normals shade correctly.

Run from root

% ./plume3d mesh_primitives

A front, raised camera looks at the row of primitives with the heightmap terrain behind. The demo captures a screenshot at frame 60 and exits at frame 80.

What it does

• Builds one of each MeshGen factory, tints the returned Mesh with setColor, and lays them out along X — each factory returns a plain Mesh you draw like any other:

  var box = MeshGen.box(1.4, 1.4, 1.4)               // AABB = ±(1.4)/2, per-face normals
  box.setColor(0.85, 0.30, 0.28, 1.0)
  
  var cyl = MeshGen.cylinder(0.75, 1.7, 28, true)    // capped, about Y
  var cone = MeshGen.cone(0.95, 1.9, 28, true)       // apex up, capped base
  var plane = MeshGen.plane(1.9, 1.9, 4, 4)          // 4×4 quads, faces +Y
  var grid = MeshGen.grid(8, 8, 0.28, 0.28)          // exactly 8×8 vertices

• Builds a sine-wave heightmap terrain — a flat list of n·n samples (row-major, X fastest) fed to MeshGen.heightmap, which displaces a grid in Y and recomputes normals:

  var n = 32
  var heights = []
  for (iz in 0...n) {
    for (ix in 0...n) {
      heights.add(((ix * 0.45).sin * (iz * 0.4).cos) * 0.6)
    }
  }
  _terrain = MeshGen.heightmap(heights, n, n, 0.6, 0.6, 1.0)
  _terrain.setColor(0.45, 0.40, 0.34, 1.0)

• Draws the terrain first, then the primitive row, each with a column-major translation matrix passed to Graphics.drawMesh:

  Graphics.drawMesh(_terrain, _shader, trans(0, -2.0, -3))
  for (it in _items) {
    Graphics.drawMesh(it[0], _shader, trans(it[1], it[2], it[3]))
  }

Notes

• Each primitive is centered at the origin, Y up — the demo positions them purely with the model matrix, never by baking an offset into the geometry.
• The lit shader proves the generated normals are correct: the box reads with hard edges (per-face normals), the cylinder/cone/heightmap shade smoothly (per-vertex normals), and the heightmap’s gentle gradients show computeNormals working on the displaced surface.
• The plane and grid are lifted and face the camera so their +Y-facing surface is visible from the front-above view.

See MeshGen for the full factory surface — plane / grid / box / cylinder / cone / heightmap, the centered/Y-up conventions, and the tangents-deferred note.