Does redirecting combat damage from a creature to a planeswalker count as combat damage for trample purposes?

When a creature with trample is blocked, the attacking player must assign lethal damage to each blocking creature before assigning any excess damage to the defending player (CR 702.19b). The key point is that trample's excess-damage calculation happens before any redirection occurs — it is determined at assignment time, not at the time damage is dealt.

Separately, a defending player may choose to redirect combat damage that would be dealt to them by an unblocked attacker to a planeswalker they control (CR 306.7). However, this redirection happens after the damage assignment step; the damage retains its combat-damage nature throughout (CR 510.1). Trample excess is already locked in before redirection is even considered.

Importantly, trample only lets excess damage go to the player (or, since the 2010 rules update, planeswalkers that player controls via the redirection rule). Damage assigned to the blocking creature to make it lethal does not change — the attacker still must assign at least lethal damage to each blocker first (CR 702.19b, 510.1c).

Concrete example: Your 5/5 trampler is blocked by a 2/2. You assign 2 damage to the 2/2 (lethal) and 3 damage to the defending player. Your opponent redirects those 3 to their planeswalker. All 3 points are still combat damage — they can trigger things like lifelink on the attacker and will remove 3 loyalty from the planeswalker.

So trample functions exactly the same whether the excess damage ultimately hits the player or is redirected to their planeswalker; the redirection does not interfere with or recalculate the trample assignment.