127 lines
5.4 KiB
Markdown
127 lines
5.4 KiB
Markdown
# U-Tad UI Project
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## Skill Tree System Implementation
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### Overview
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A complete skill tree system with node-based progression, prerequisite validation, visual connection lines, and data-driven configuration.
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---
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## Architecture: Blueprint Decision
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### Blueprint Implementation
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**Components:** `WBP_SkillTree`, `WBP_SkillNode`, `WBP_SkillNodeTooltip`
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**Reasoning:**
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- **Iteration speed**: UI layout and styling require rapid visual iteration
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- **Designer-friendly**: Artists/designers can modify UI without C++ knowledge
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---
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## Core Systems
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### 1. Data Layer (`SkillTreeTypes.h`)
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**Structures:**
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- `FSkillNodeData`: Skill definition row for skill data table (name, cost, prerequisites, effects, starting flag)
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- `FSkillNodeRuntime`: Runtime state wrapper
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- `ESkillNodeState`: State enum (Locked, Available, Selected, Purchased)
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**Decision**: Data Table-driven design allows non-programmers to configure skills without recompiling.
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### 2. Logic Layer (`SkillTreeComponent`)
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**Responsibilities:**
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- Skill tree initialization from DataTable
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- State management (prerequisites, affordability checks)
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- Selection validation and purchase confirmation
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- Starting skills auto-purchase
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- Skill point management
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- Effect application hooks
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**Key Features:**
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- **Purchase order sorting**: Ensures prerequisites are purchased before dependents
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- **Cascade deselection**: Removing a prerequisite deselects dependent skills
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- **Starting skills**: Marked in DataTable, auto-purchased at init, preserved on reset
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- **Stat aggregation**: Provides `GetTotal[Stat]Bonus()` functions to sum all purchased skills' bonuses
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### 3. Stats Integration Layer (`CharacterStatsComponent`)
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**Responsibilities:**
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- Automatic stat calculation from purchased skills
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- Character stat management (Health, Damage, Speed)
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- Real-time updates when skills are purchased
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- Movement speed integration
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**How it works:**
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- Finds SkillTreeComponent on same actor at BeginPlay
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- Listens to `OnSkillPurchased` event
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- Iterates all purchased skills, sums flat + percentage bonuses
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- Applies formula: `FinalStat = Base + FlatBonus + (Base * PercentBonus / 100)`
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- Auto-updates CharacterMovementComponent speed
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- Broadcasts stat change events for UI updates
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**Decision**: Separate stats component keeps concerns separated - SkillTreeComponent handles progression, CharacterStatsComponent handles stat application. Makes both reusable independently.
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### 4. Visualization Layer (`SkillTreeConnectionsWidget`)
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**Responsibilities:**
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- Automatic line drawing between prerequisite nodes (You only need to place nodes in the UI!)
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- Dynamic line coloring based on skill states
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- Event-driven refresh on state changes
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**Technical Approach:**
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- **Generic search**: Works with any widget hierarchy so designers/artist are not limited when creating the skill tree widget (Canvas, Overlay, Grid)
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- **NativePaint override**: Direct Slate rendering for performance
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- **Delegate binding**: Auto-refreshes when skills change state
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**Decision**: Single self-contained widget eliminates manual line management and Blueprint complexity.
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### 5. UI Layer (Blueprints)
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**WBP_SkillNode & WBP_SkillNodeTooltip:**
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- Displays skill icon, state, cost
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- Handles click events (select/deselect)
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- Stores SkillID for runtime lookup
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- Custom tooltip support to display skill details
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- Real time state updates via event binding allows real-time visual feedback
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**WBP_SkillTree:**
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- Contains manually-placed skill nodes
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- References SkillTreeComponent
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- Hosts SkillTreeConnectionsWidget which draws lines between nodes automatically
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- Binds to component events for UI updates
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**Decision**: Manual node placement allows custom layouts (linear, radial, branching) per designer preference.
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---
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## Key Design Decisions
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### 1. Skill prerequisites in DataTable
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**Alternative**: Hard-coded in C++ or DataAssets references
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**Chosen**: DataTable array
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**Reason**: Designers can modify skill dependencies without programmer intervention and without recompiling
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### 2. Component vs Subsystem
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**Alternative**: Game Instance Subsystem
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**Chosen**: Actor Component
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**Reason**: Supports multiple skill trees per player (e.g., combat tree, crafting tree) and easier save/load integration
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### 3. Single Connections Widget
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**Alternative**: Individual line widgets per connection with manual management
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**Chosen**: One widget draws all lines automatically
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**Reason**: Eliminates array management, better performance, automatic coordinate handling
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### 4. Separate Stats Component
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**Alternative**: Apply stats directly in SkillTreeComponent
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**Chosen**: Separate CharacterStatsComponent
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**Reason**: Separation of concerns - SkillTreeComponent is reusable for any progression system, CharacterStatsComponent specifically handles character stats. Allows skill trees without stat bonuses, or stats without skill trees.
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---
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## Technical Highlights
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- **Event-driven architecture**: Component broadcasts state changes, UI responds automatically
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- **State machine validation**: Prevents invalid transitions (e.g., can't select locked skills)
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- **Automatic stat application**: CharacterStatsComponent listens to skill purchases, recalculates stats, applies to character
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- **Geometry-aware rendering**: Lines adapt to any widget positioning system
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- **Data-driven configuration**: Zero code changes and no need to compile for new skills or tree layouts
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- **Reset functionality**: Refunds non-starting skills, maintains starting points
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- **Modular design**: Skill progression, stats, and visualization are independent
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