Convert model geometry to Zig

1 files changed, 90 insertions, 0 deletions

diff --git a/src/model.zig b/src/model.zig
new file mode 100644
index 0000000..274176d
--- /dev/null
+++ b/src/model.zig
@@ -0,0 +1,90 @@
+// 3D model
+// Copyright (C) 2002  David Rosen
+// Copyright (C) 2023  Nguyễn Gia Phong
+//
+// This file is part of Black Shades.
+//
+// Black Shades is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published
+// by the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Black Shades is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Black Shades.  If not, see <https://www.gnu.org/licenses/>.
+
+const XYZ = geom.XYZ;
+const degToRad = std.math.degreesToRadians;
+const floatMax = std.math.floatMax;
+const geom = @import("geom.zig");
+const rotate2d = geom.rotate2d;
+const segCrossSphere = geom.segCrossSphere;
+const segCrossTrigon = geom.segCrossTrigon;
+const sqr = geom.sqr;
+const std = @import("std");
+
+const max_trigons = 400;
+
+const Trigon = extern struct {
+    vertices: [3]u32,
+    r: f32,
+    g: f32,
+    b: f32,
+};
+
+pub const Model = extern struct {
+    vertices: [max_trigons * 3]XYZ,
+    vertices_len: u32,
+    normals: [max_trigons]XYZ,
+    trigons: [max_trigons]Trigon,
+    trigons_len: u32,
+    center: XYZ,
+    radius: f32,
+    vert_array: [max_trigons * 27]f32,
+};
+
+pub export fn segCrossModel(start: XYZ, end: XYZ, m: *const Model,
+                        intersection: *XYZ) c_int {
+    if (!segCrossSphere(start, end, m.center, m.radius))
+        return -1;
+    const p: @Vector(3, f32) = @bitCast(start);
+    var result: c_int = -1;
+    var shortest = floatMax(f32);
+    for (0..m.trigons_len) |j| {
+        var v: @Vector(3, f32) = undefined;
+        if (!segCrossTrigon(start, end,
+                            &m.vertices[m.trigons[j].vertices[0]],
+                            &m.vertices[m.trigons[j].vertices[1]],
+                            &m.vertices[m.trigons[j].vertices[2]],
+                            &m.normals[j], @ptrCast(&v)))
+            continue;
+        const distance = @reduce(.Add, sqr(v - p));
+        if (distance < shortest or result == -1) {
+            shortest = distance;
+            result = @intCast(j);
+            intersection.* = @bitCast(v);
+        }
+    }
+    return result;
+}
+
+pub export fn segCrossModelTrans(start: XYZ, end: XYZ, m: *const Model, 
+                                 move: XYZ, rot: f32,
+                                 intersection: *XYZ) c_int {
+    const t: @Vector(3, f32) = @bitCast(move);
+    var p = @as(@Vector(3, f32), @bitCast(start)) - t;
+    rotate2d(&p[2], &p[0], degToRad(f32, -rot));
+    var q = @as(@Vector(3, f32), @bitCast(end)) - t;
+    rotate2d(&q[2], &q[0], degToRad(f32, -rot));
+
+    defer {
+        rotate2d(&intersection.z, &intersection.x, degToRad(f32, rot));
+        intersection.* = @bitCast(@as(@Vector(3, f32),
+                                      @bitCast(intersection.*)) + t);
+    }
+    return segCrossModel(@bitCast(p), @bitCast(q), m, intersection);
+}