Does Vayne's Tumble (Q) damage affect Trinity Force?
To your first question: Yes it does trigger the spellblade effect.
For your second question:
No, it does not affect spellblade! You are misunderstanding how Trinity Force (or spellblades in general) works.
Trinity force will give you 200% of your Base AD as bonus damage. The bonus damage cannot be increased through Items, Ablities or Runes/Masteries. The only thing that actually works is Base AD. This means for a level 18 Vayne with 109 base damage TF will exactly deal 218 Physical bonus damage. It does not benefit from crit or spells and is simply added to the damage you'd deal anyways.
So basically what would happen:
If you have a fully maxed Q and 200 AD with 100 Base AD You would deal:
200/400 (basic attack/crit) +
200 x 0.5 (bonus damage from tumble) +
100 * 2 (bonus damage from TF)
500 damage with a normal Attack or 700 with a crit since both the Tumble and the spellblade bonus damage don't benefit from crit.
- Yes
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No. Because the passive is:
Unique Passive - Spellblade: After using an ability, your next basic attack deals 200% base AD bonus physical damage. (1.5 second cooldown).
Trinity doesn't increase the dmg you deal, it deals bonus dmg the more AD you have (that's why the passive says bonus physical damage). So the calculation is:
(100 * 1.50) + (100 * 2) = 350