Perspective projection

src/graphics/transform.zig

@@ -0,0 +1,53 @@
+const std = @import("std");
+const Transform = @This();
+
+// TODO: Rotation
+
+position: @Vector(3, f32) = @splat(0.0),
+rotation: @Vector(3, f32) = @splat(0.0),
+scale: @Vector(3, f32) = @splat(1.0),
+
+pub fn matrix(transform: Transform) @Vector(16, f32) {
+    return .{
+        1.0, 0.0, 0.0, transform.position[0],
+        0.0, 1.0, 0.0, transform.position[1],
+        0.0, 0.0, 1.0, transform.position[2],
+        0.0, 0.0, 0.0, 1.0,
+    };
+}
+
+pub fn inverse(transform: Transform) @Vector(16, f32) {
+    // TODO: Could we just translate, rotate and scale back instead of relying on matrix math?
+    return invertMatrix(transform.matrix());
+}
+
+fn invertMatrix(a: @Vector(16, f32)) @Vector(16, f32) {
+    const MOD: f32 = 1.0 / 16.0;
+    const ID = @Vector(16, f32){
+        1, 0, 0, 0,
+        0, 1, 0, 0,
+        0, 0, 1, 0,
+        0, 0, 0, 1,
+    };
+    var p = ID - @as(@Vector(16, f32), @splat(MOD)) * a;
+    var output = ID + p;
+    inline for (0..8) |_| {
+        p = multiplyMatrix(p, p);
+        output = multiplyMatrix(output, ID + p);
+    }
+    return output * @as(@Vector(16, f32), @splat(MOD));
+}
+
+pub fn multiplyMatrix(a: @Vector(16, f32), b: @Vector(16, f32)) @Vector(16, f32) {
+    var output: @Vector(16, f32) = [1]f32{0.0} ** 16;
+
+    @setFloatMode(.optimized);
+    for (0..4) |row| {
+        for (0..4) |col| {
+            for (0..4) |i| {
+                output[row * 4 + col] += a[row * 4 + i] * b[i * 4 + col];
+            }
+        }
+    }
+    return output;
+}