praca_magisterska/games/unreal/tutorial/part-3-create-bullet.md

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# Part 3: Create the Bullet
[← Previous: Part 2 - Create the Player](part-2-create-player.md) | [Back to Index](README.md) | [Next: Part 4 - Create the Enemy →](part-4-create-enemy.md)
---
## Step 3.1: Create Bullet Blueprint
1. In Content Browser → Blueprints folder
2. Right-click → **Blueprint Class****Actor**
3. Name it: `BP_Bullet`
4. Double-click to open
5. **Add Components:**
- Paper Sprite → name `BulletSprite`
- Sphere Collision → name `BulletCollision`
- Radius: `8`
- Generate Overlap Events: **CHECKED**
- Collision Preset: Custom → Query Only
- Cube (Static Mesh) → name `TempVisual`
- Scale: `(0.1, 0.1, 0.05)` - small bullet-sized cube
- This provides visibility until proper visuals in [Part 9](part-9-final-setup.md)
6. **Create Variables:**
| Variable Name | Type | Default Value |
|---------------|------|---------------|
| `TravelDirection` | Vector | (0, 1, 0) |
| `TravelSpeed` | Float | 1200.0 |
| `RemainingLifetime` | Float | 4.0 |
| `IsEnemyProjectile` | Boolean | false |
| `Damage` | Integer | 1 |
### Expected Result after Compile:
- Compile button shows GREEN checkmark
- Components panel shows: DefaultSceneRoot → BulletSprite, BulletCollision, TempVisual
- Variables panel shows all 5 variables with correct types
### Expected Result in Viewport (Blueprint Editor):
- Small cube visible (the TempVisual placeholder)
- Sphere collision visible (radius 8)
---
## Step 3.2: Bullet Movement Logic
1. In Event Graph, from **Event Tick:**
#### a) Calculate movement:
1. Right-click → `Get TravelDirection`
2. Right-click → `Get TravelSpeed`
3. Right-click → search `Multiply (Vector * Float)` → add it
- Connect TravelDirection to the Vector input
- Connect TravelSpeed to the Float input
- Result: a vector representing full speed in travel direction
4. Right-click → `Get World Delta Seconds`
5. Right-click → search `Multiply (Vector * Float)` → add another one
- Connect the RESULT from step 3 to the Vector input
- Connect World Delta Seconds to the Float input
- Result: movement delta for this frame (frame-rate independent)
6. Right-click → `Get Actor Location`
7. Right-click → search `Add (Vector + Vector)` → add it
- Connect Actor Location to first input
- Connect the movement delta (from step 5) to second input
8. Right-click → `Set Actor Location`
- Connect the Add result to "New Location"
- Connect execution wire from Event Tick to Set Actor Location
#### b) Check lifetime and destroy when expired:
9. Right-click → `Get RemainingLifetime`
10. Right-click → `Get World Delta Seconds`
11. Right-click → search `Subtract (Float)` → add it
- Connect RemainingLifetime to the TOP input (A)
- Connect World Delta Seconds to the BOTTOM input (B)
- Result: RemainingLifetime minus DeltaSeconds
12. Right-click → `Set RemainingLifetime`
- Connect the Subtract result to it
- This ALWAYS stores the new decreased lifetime value
13. Connect execution wire:
- From `Set Actor Location` (from step 8) → `Set RemainingLifetime`
14. Right-click → search `<= (Float)` (less than or equal) → add it
- Connect RemainingLifetime (from Set node output, or Get again) to TOP input
- Type `0` in BOTTOM input
- Result: true if lifetime has expired
15. From `Set RemainingLifetime`, drag execution → `Branch`
- Connect the `<=` result to Branch's "Condition" input
16. **On TRUE (lifetime expired):**
- From Branch's "True" pin, drag → `Destroy Actor`
- Target: leave as "Self" (destroys this bullet)
17. **On FALSE (still alive):**
- Leave unconnected (bullet continues to exist, will check again next frame)
**Visual:**
```
Event Tick ──► Set Actor Location ──► Set RemainingLifetime ──► Branch
(movement) = Remaining - Delta (Remaining <= 0?)
TRUE ──────┴────── FALSE
│ │
▼ ▼
Destroy Actor (nothing)
```
### 2. CREATE "Initialize" FUNCTION:
#### a) Add input parameters:
| Parameter | Type | Default |
|-----------|------|---------|
| `Direction` | Vector | - |
| `Speed` | Float | - |
| `bIsEnemy` | Boolean | - |
| `Lifetime` | Float | - |
| `DamageValue` | Integer | 1 |
#### b) Inside:
- Normalize Direction → Set TravelDirection
- Set TravelSpeed = Speed
- Set IsEnemyProjectile = bIsEnemy
- Set RemainingLifetime = Lifetime
- Set Damage = DamageValue
### 3. Compile and Save
### Expected Result after Compile:
- Compile button shows GREEN checkmark
- "Initialize" function appears under Functions with 5 input parameters
> **NOTE:** Bullet testing is possible after completing [Step 3.4](#step-34-complete-player-firing-logic-bp_player).
---
## Step 3.3: Bullet Collision Logic
### 1. ADD THE OVERLAP EVENT:
1. In the Components panel (top-left), click on **"BulletCollision"** to select it
2. In the Details panel (right side), scroll down to find the **"Events"** section
- Look for "On Component Begin Overlap"
- Click the green **"+"** button next to it
- This creates an event node in the Event Graph
3. The Event Graph now shows a red node: **"On Component Begin Overlap (BulletCollision)"**
- This fires whenever another actor overlaps with the bullet's collision sphere
### 2. CHECK IF THIS IS AN ENEMY PROJECTILE:
4. Right-click → `Get IsEnemyProjectile`
- This gets your boolean variable
5. From "On Component Begin Overlap", drag execution → `Branch`
- Connect IsEnemyProjectile to Branch's "Condition" input
- TRUE = this is an enemy bullet (should damage player)
- FALSE = this is a player bullet (should damage enemies)
### 3. TRUE BRANCH - Enemy Bullet Hits Player:
6. From the **"On Component Begin Overlap"** node, look for the **"Other Actor"** output pin
- This is the actor that overlapped with the bullet
- Drag from "Other Actor" → search `Cast to BP_Player`
7. Connect execution wire:
- From Branch **TRUE** pin → `Cast to BP_Player`
8. The cast has two execution outputs:
- **"Cast Succeeded"** (top) - the other actor IS a player
- **"Cast Failed"** (bottom) - the other actor is NOT a player
9. From "Cast Succeeded", we need to damage the player:
- From the cast's **"As BP Player"** output pin, drag → search `TakeHit`
- This calls the TakeHit function you created in [Part 2](part-2-create-player.md)
- **IMPORTANT:** The "Target" pin on TakeHit should now be connected to "As BP Player" (this happened automatically when you dragged from that pin)
- If Target shows "self", you must manually connect "As BP Player" to the "Target" pin - TakeHit must be called ON the player, not on the bullet!
10. Connect the Damage parameter:
- Right-click → `Get Damage` (your bullet's damage variable)
- Connect to TakeHit's "DamageAmount" input
11. After damaging the player, destroy the bullet:
- From TakeHit, drag execution → `Destroy Actor`
- Leave "Target" as "Self" (destroys this bullet)
12. Connect execution wire:
- Cast to BP_Player → TakeHit → Destroy Actor
### 4. FALSE BRANCH - Player Bullet Hits Enemy (PLACEHOLDER):
> **NOTE:** BP_Enemy doesn't exist yet, so we'll add a placeholder. You'll complete this logic in [Part 4, Step 4.7](part-4-create-enemy.md#step-47-complete-bullet-collision-logic-bp_bullet).
13. From Branch **FALSE** pin, drag execution → `Print String`
- In the "In String" field, type: `TODO: Damage enemy`
- This is temporary - we'll replace it with real enemy damage logic in Part 4
**Visual:**
```
┌──────────────────────────────────────┐
│ On Component Begin Overlap │
│ (BulletCollision) │
│ Other Actor ○─────────────────────┐
└──────────────┬───────────────────────┘ │
│ │
▼ ▼
┌─────────────────┐ ┌──────────────────┐
│ Branch │ │ Cast to BP_Player│
│ IsEnemyProjectile └────────┬─────────┘
└───────┬───┬─────┘ │
│ │ Cast Succeeded
TRUE ─┘ └─ FALSE │
│ │ ▼
▼ │ ┌──────────────────┐
Cast to BP_Player │ │ TakeHit │
(see above) │ │ Damage: Damage │
│ └────────┬─────────┘
▼ │
┌──────────────────┐ ▼
│ Print String │ ┌──────────────────┐
│ "TODO: Damage │ │ Destroy Actor │
│ enemy" │ │ (Self) │
└──────────────────┘ └──────────────────┘
```
### 4. Compile and Save
### Expected Result after Compile:
- Compile button shows GREEN checkmark
- Event Graph shows "On Component Begin Overlap" event connected to Branch
> **NOTE:** Collision testing requires player firing (Step 3.4) and enemies (Part 4). Full collision behavior is testable after completing [Part 4](part-4-create-enemy.md).
---
## Step 3.4: Complete Player Firing Logic (BP_Player)
Now that BP_Bullet exists, we can complete the player's firing functions.
### 1. Open BP_Player Blueprint:
- In Content Drawer, navigate to Content → Blueprints
- Double-click "BP_Player" to open the Blueprint Editor
### 2. SET THE BULLET CLASS VARIABLE:
1. In My Blueprint panel, find the `BulletClass` variable
2. Click on it to select it
3. In Details panel, find "Default Value"
4. Click the dropdown and select `BP_Bullet`
5. Compile to save the change
### 3. CREATE SPAWN BULLET FUNCTION:
#### a) In "My Blueprint" panel, under "Functions", click "+"
#### b) Name the function `SpawnBullet`
#### c) Double-click to open function graph
#### d) Add input parameters to the function:
- In the function graph, look at the purple "SpawnBullet" entry node
- In Details panel (right side), find "Inputs" section
- Click "+" to add a new input parameter
| Parameter | Type |
|-----------|------|
| `SpawnLocation` | Vector |
| `Direction` | Vector |
The entry node should now show two input pins: SpawnLocation and Direction
#### e) Build the spawning logic:
1. Right-click → search `Spawn Actor from Class` → add it
2. For the "Class" input:
- Right-click → `Get BulletClass` (your variable)
- Connect BulletClass output (blue pin) to SpawnActor's "Class" input (purple pin)
3. For the "Spawn Transform Location" input:
- On the SpawnActor node, look for "Spawn Transform Location" (orange pin)
- If you only see "Spawn Transform", right-click on it → "Split Struct Pin" to expand it
- Drag a wire from the **SpawnLocation** parameter (on the SpawnBullet entry node) to **"Spawn Transform Location"**
- Leave Rotation and Scale at defaults (0,0,0 and 1,1,1)
4. Connect execution wire:
- Drag from SpawnBullet entry node (white triangle) → SpawnActor (white triangle)
#### f) Initialize the spawned bullet:
5. Add the Cast node:
- From SpawnActor's **"Return Value"** output (blue pin on right side), drag → search `Cast to BP_Bullet`
- Connect "Return Value" to the Cast's "Object" input
6. Connect execution wire:
- From SpawnActor (white triangle output) → Cast to BP_Bullet (white triangle input)
7. Add the Initialize call:
- From the Cast's **"As BP Bullet"** output (blue pin), drag → search `Initialize`
- This calls the Initialize function you created in Step 3.2
- **IMPORTANT:** The "Target" pin should automatically connect to "As BP Bullet"
8. Connect Initialize parameters:
- **Direction**: Drag from the **Direction** parameter (on SpawnBullet entry node, yellow pin) → Initialize's "Direction" input
- **Speed**: Right-click → `Get BulletSpeed` → connect to Initialize's "Speed" input
- **bIsEnemy**: Leave unchecked (false) - player bullets aren't enemy projectiles
- **Lifetime**: Type `4.0` in the input field (or leave default)
- **DamageValue**: Leave at default `1`
9. Connect execution wire:
- From Cast to BP_Bullet → Initialize
**Visual:**
```
┌───────────────────────┐ ┌─────────────────────────────────┐
│ SpawnBullet │─────►│ Spawn Actor from Class │
│ SpawnLocation ○───────┼─────►│ Class: BulletClass │
│ Direction ○ │ │ Spawn Transform Location ○◄───┘
└───────────────────────┘ │ Return Value ○────────────────┐
└─────────────────────────────────┘
┌─────────────────────┘
┌─────────────────────────┐
│ Cast to BP_Bullet │
│ Object ○◄─────────────┘
│ As BP Bullet ○────────┐
└─────────────────────────┘
┌─────────────┘
┌─────────────────────────┐
│ Initialize │
│ Target ○◄─────────────┘
│ Direction ○◄──────────── (from entry node)
│ Speed ○◄────────────── BulletSpeed
│ bIsEnemy: false │
│ Lifetime: 4.0 │
└─────────────────────────┘
```
#### g) Compile (should have no errors now)
### 4. CREATE FIRE VOLLEY FUNCTION:
#### a) In "My Blueprint" panel, under "Functions", click "+"
#### b) Name the function `FireVolley`
#### c) Double-click to open function graph
#### d) Inside FireVolley function graph, build this logic step by step:
---
**STEP 1 - Get the volley size and check for single bullet case:**
1. You should see a purple "FireVolley" entry node on the left
- This is where execution starts when the function is called
2. Right-click → search `Get VolleySize` → add it
- This gets your variable value (default 3)
3. Right-click → search `Equal (Integer)` or `==` → add it
- Connect VolleySize output to the TOP input (A)
- Type `1` in the BOTTOM input (B)
- This checks: is VolleySize exactly 1?
4. From FireVolley entry node, drag execution → `Branch`
- Connect the == result to Branch's "Condition" input
- TRUE = single bullet, FALSE = multiple bullets in spread
---
**STEP 2 - TRUE branch: Fire single bullet straight up:**
5. From Branch TRUE pin, drag execution → right-click → search `SpawnBullet` (the function you created in step 3 above)
6. For SpawnBullet's "Spawn Location" input:
- Right-click → `Get Actor Location`
- Connect the output to Spawn Location
7. For SpawnBullet's "Direction" input (fire straight UP):
- Right-click → `Make Vector`
- Set X = 1 (up in top-down view)
- Set Y = 0
- Set Z = 0
- Connect to Direction input
8. After SpawnBullet, drag execution → `Return Node`
- This exits the function early (don't continue to the loop)
**Visual so far:**
```
┌─────────────┐ ┌────────────────────┐
│ FireVolley │─────►│ Branch │
│ (entry) │ │ VolleySize == 1 │
└─────────────┘ └─────────┬──────────┘
│ TRUE
┌─────────────────────┐
│ SpawnBullet │
│ Location: ActorLoc │───► Return
│ Direction: (1,0,0) │
└─────────────────────┘
```
---
**STEP 3 - FALSE branch: Fire multiple bullets in a spread pattern:**
9. From Branch FALSE pin, we need to loop through each bullet.
First, calculate the starting angle:
The spread is CENTERED on "straight up". For 3 bullets with 12° spread:
- Bullet 0: -12° (left of center)
- Bullet 1: 0° (center, straight up)
- Bullet 2: +12° (right of center)
**Formula:** `StartAngle = -(VolleySpread * (VolleySize - 1)) / 2`
10. **Calculate StartAngle:**
- Right-click → `Get VolleySize`
- Right-click → `Subtract (Integer)` → connect VolleySize, type `1`
- Result: (VolleySize - 1) = 2 for default
- Right-click → `Get VolleySpread`
- Right-click → `Multiply (float)` → connect VolleySpread and (VolleySize-1)
- NOTE: The integer will auto-convert to float
- Result: VolleySpread * (VolleySize - 1) = 12 * 2 = 24
- Right-click → `Divide (float)` → connect the multiply result, type `2`
- Result: 24 / 2 = 12
- Right-click → `Negate (float)` or "Multiply by -1"
- Result: -12 (this is StartAngle)
- Right-click → `Set` → create a LOCAL variable "StartAngle" (Float)
- OR just keep the wire connected (we'll use it in the loop)
11. **Set up the FOR loop:**
- From Branch FALSE pin, drag → right-click → search `For Loop`
- "First Index": type `0`
- "Last Index": connect (VolleySize - 1)
- You already calculated this in step 10, reuse it or calculate again:
- Get VolleySize → Subtract 1 → connect to Last Index
The loop will run with Index = 0, 1, 2 for VolleySize=3
12. **Inside the loop (from "Loop Body" execution pin):**
Calculate angle for THIS bullet:
- Right-click → `Multiply (float)`
- Connect loop "Index" to first input (auto-converts int to float)
- Connect VolleySpread to second input
- Result: Index * VolleySpread (0, 12, 24 for indices 0, 1, 2)
- Right-click → `Add (float)`
- Connect StartAngle (the -12 from step 10) to first input
- Connect (Index * VolleySpread) to second input
- Result: StartAngle + (Index * VolleySpread) = -12, 0, +12 degrees
This is the angle in DEGREES. Store or continue with this value.
13. **Convert angle from degrees to a direction vector:**
In Unreal's top-down view (looking down Z axis):
- X axis = up/down on screen (vertical)
- Y axis = left/right on screen (horizontal)
- Angle 0° = straight up = direction (1, 0, 0)
- Angle 90° = right = direction (0, 1, 0)
```
Direction.X = Cos(angle) // Cos for vertical (forward/up)
Direction.Y = Sin(angle) // Sin for horizontal offset
Direction.Z = 0
```
BUT Unreal's Sin/Cos use RADIANS, not degrees!
**a) Convert degrees to radians:**
- Right-click → search `Degrees To Radians` → add it
- Connect your angle (from step 12) to the input
- Output is angle in radians
**b) Calculate X component (Cos - forward/up direction):**
- Right-click → `Cos (Radians)` → add it
- Connect the Degrees To Radians output to Cos input
**c) Calculate Y component (Sin - horizontal offset):**
- Right-click → `Sin (Radians)` → add it
- To connect the SAME radians value to Sin (without losing the Cos connection):
- **Option 1:** Ctrl+drag from "Degrees To Radians" output to Sin input (creates second wire)
- **Option 2:** Drag directly from "Degrees To Radians" output again - UE5 allows multiple wires from one output pin
- Both Cos and Sin should now be connected to the same radians value
**d) Make the direction vector:**
- Right-click → `Make Vector`
- Connect Cos result to X (forward/up direction)
- Connect Sin result to Y (horizontal spread)
- Set Z = 0
14. **Spawn the bullet:**
- From the loop body execution, drag → `SpawnBullet` (from step 3)
- Spawn Location: `Get Actor Location`
- Direction: Connect the Make Vector from step 13
15. **Connect loop completion:**
- The For Loop has a "Completed" execution pin
- This fires AFTER all iterations are done
- Drag from "Completed" → `Return Node` (or leave unconnected)
**Complete Visual:**
```
┌─────────────┐ ┌────────────────────┐
│ FireVolley │─────►│ Branch │
│ (entry) │ │ VolleySize == 1 │
└─────────────┘ └──────┬───────┬─────┘
│TRUE │FALSE
▼ ▼
┌──────────┐ ┌─────────────────────────────┐
│SpawnBullet│ │ Calculate StartAngle │
│Dir:(1,0,0)│ │ = -(Spread*(Size-1))/2 │
└─────┬────┘ └──────────────┬──────────────┘
│ ▼
▼ ┌─────────────────┐
Return │ For Loop │
│ 0 to Size-1 │
└───────┬─────────┘
│ Loop Body
┌──────────────────────────────┐
│ Angle = Start + (i * Spread) │
│ Radians = DegreesToRadians │
│ Dir.X = Cos(Radians) │
│ Dir.Y = Sin(Radians) │
│ SpawnBullet(Location, Dir) │
└──────────────────────────────┘
```
**Test Values (VolleySize=3, VolleySpread=12):**
- StartAngle = -(12 * 2) / 2 = -12°
- Bullet 0: -12 + (0 * 12) = -12° → slightly left
- Bullet 1: -12 + (1 * 12) = 0° → straight up
- Bullet 2: -12 + (2 * 12) = +12° → slightly right
### 5. CONNECT FIREVOLLEY TO THE FIRE RATE LIMITER:
1. Go back to the Event Graph tab
2. Find your IA_Fire logic from [Step 2.5](part-2-create-player.md#step-25-create-player-firing-logic)
3. Delete the Print String "FIRE!" placeholder
4. From the "Set FireTimer = FireInterval" node, drag execution → `FireVolley`
**Updated Visual:**
```
┌─────────────────┐ TRUE ┌─────────────────────┐
│ Branch │───────────►│ Set FireTimer │──► FireVolley
│ FireTimer <= 0 │ │ = FireInterval │
└─────────────────┘ └─────────────────────┘
```
### 6. Compile and Save
### Expected Result after Compile:
- Compile button shows GREEN checkmark
- "FireVolley" and "SpawnBullet" functions appear under Functions in My Blueprint panel
### Expected Result in Play mode:
- Pressing Z or Left Mouse Button spawns 3 bullets in a spread pattern
- Bullets travel upward from player position
- Rapid fire when holding the button (every 0.08 seconds)
- Bullets disappear after 4 seconds (RemainingLifetime)
---
[← Previous: Part 2 - Create the Player](part-2-create-player.md) | [Back to Index](README.md) | [Next: Part 4 - Create the Enemy →](part-4-create-enemy.md)