A stored projection whose determinant is not finite is read back as the
same map divided by the largest magnitude in its w row, the scale the
overflow branch of conjugated already uses, so points that overflowed at
the stored scale draw: the identity with every entry 1e308 maps (2, 2)
to (2, 2). The overflow branch of inverse scales the map so that the
largest of the products its determinant sums is near 1, so a map with
large entries and a small w row, such as a scale by 1e305 with a move
by -3.9e307, is still inverted and read back.
The two overflow tests in persp_text.rs build their stored projections
with a w row of 1, so they still overflow after the read-back.
Homography::from_array accepted nine finite numbers only when det().abs()
was above 1e-15. With large entries the determinant can be inf - inf, so a
valid stored projection was rejected on reading and its type drew flat, or
it can overflow to inf, so a projection that cannot be inverted was
accepted.
When the determinant is not finite, inverse() now inverts a copy divided
by a power of two (largest entry between 0.5 and 1), and treats that copy
as not invertible when its determinant is at most 1e-15 times the largest
of the six products it sums. from_array and the overflow path of
conjugated accept such a map only when that inverse exists. Maps with a
finite determinant are judged as before.
Follows #4912.
Homography::then_after returned products whose entries could overflow to
infinity or become NaN. A move, transform or grid reproject of type or a
symbol instance whose stored projection has large finite entries stored such
a product, and the type was then drawn flat, since a projection that is not
finite reads as none.
- Homography::checked_then_after returns None when an entry of the product
is not finite.
- project_node composes each type and symbol instance projection with it and
returns false, leaving the object as it is, when one would not be finite;
moves and transforms in perspective and Define Perspective Grid with
reproject then return the horizon error and leave the document unchanged.
- transform_map, attach_homography and size_homography return None for such
a product.
- Edit Text returns the horizon error, and does not enter isolation mode,
when the type cannot be shown flat where it is drawn.
When the conjugate a ∘ self ∘ a⁻¹ overflows, conjugated now forms every
entry of the product as a sum of terms whose factors are split into a
mantissa and a power of two, and scales the whole product by one power of
two from its w row at the end. Scaling each partial product to a largest
entry of 1 could round an entry to 0 that the next factor would restore,
so a projection with entries far apart in size, such as a scale by
(1e160, 1e-160) seen through the same scale, was removed and the art drew
flat.
When the conjugate of a projection overflows, it is now formed one factor
at a time, and each partial product is divided by its largest entry
magnitude. Scaling the affine factors up front let the w row underflow to
0, so a scale by 2 seen through a move by 1e308 returned None and the
projection was removed, though its conjugate is finite.
When conjugating a projection overflows, the scaled-down result is now divided by the largest entry in its w row. A valid conjugate is no longer dropped by the determinant cutoff at the arbitrary scale, and every point of a kept projection passes the horizon test in apply instead of none.
When moving type or a symbol instance in perspective makes the
conjugated projection overflow, Homography::conjugated now forms the
product from factors scaled to a largest entry of 1 and returns it at
that scale, which maps every point to the same place. When even the
scaled result is not invertible, the transform removes the projection
and the art is drawn flat, instead of keeping the old projection while
the flat art moves.
Homography::apply checked that w is in front of the horizon but not the quotients, so a point with w just above 1e-9 and a large x or y, or a NaN w, mapped to an infinite or NaN point. apply now returns None unless the mapped point is finite. inverse, conjugated and affine_at return None when their result has an entry that is not finite.
Type and symbol instances attached to a plane keep their art and carry a projection
(Node.perspective.projection, append-only); the canvas and every export draw their outlines
through it (reshape/bake), so they are foreshortened and stay type and symbol instances. Bounds,
hit testing and transforms follow the projection. Object › Perspective › Edit Text
(perspective.editText, or double-clicking with the Perspective Selection tool) shows the type flat
where it is drawn in isolation mode; exiting isolation projects it again. Release with
Perspective keeps their look. Copies, pastes, duplicates and Selection-tool moves keep the
attachment (the art moves as dragged). Flare, spiral and polar grid draw on the active plane, and
so do the click-to-size shape dialogs (perspective.draw `at`: sizes in plane units).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The Perspective Selection tool shows the selection's bounding box in perspective; its handles
scale in plane space (perspective.transform; Shift proportional, Alt from the centre). Alt-drag
moves copies that stay attached, pressing 5 while dragging moves along the plane's normal
(ToolKey::Digit, delivered by the canvas and MCP press_key), and the arrow keys nudge in
perspective (perspective.nudge). Transform Again repeats the last perspective move or scale in
plane space. Attachments (plane and depth) now live on the objects (Node.perspective), so copies,
duplicates and pastes keep them; grids from older files hand theirs over. Homography moves to
vectorcraft-geom. Hint-bar text for the tool.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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