How to create 3D models and characters in Scratch
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3DModeler_Chris
Posted on January 28, 2024 • Advanced
🐱 How to create a 3D cat model in Scratch?
Hey 3D graphics experts! I’m trying to create a realistic 3D cat character in Scratch, but I’m completely lost on where to start. I’ve seen amazing 3D projects on Scratch but have no idea how they work.
- Want to understand the fundamentals of 3D rendering in Scratch
- Need to learn about raycasting and 3D projection
- Looking for step-by-step guidance on building 3D models
- Want to make the cat interactive and animated
Can someone break down the complex 3D concepts into manageable steps? I’m ready to learn advanced programming! 🎯
RaycastingExpert_Maya
Replied 3 hours later • ⭐ Best Answer
Great question @3DModeler_Chris! Creating 3D models in Scratch is definitely advanced, but totally achievable. Here’s a comprehensive guide:
🎯 Understanding 3D Basics
First, understand that Scratch is 2D, so we simulate 3D through mathematical projection:
// Basic 3D to 2D projection define project 3d point (x3d) (y3d) (z3d) set [camera distance v] to [200] set [screen x v] to (((x3d) * (camera distance)) / ((z3d) + (camera distance))) set [screen y v] to (((y3d) * (camera distance)) / ((z3d) + (camera distance))) go to x: (screen x) y: (screen y)
🏗️ Building a 3D Cat Structure
Start with basic geometric shapes and combine them:
// Cat model data structure when flag clicked set [cat vertices v] to [] set [cat faces v] to [] // Define cat head vertices (simplified) add [0 50 0] to [cat vertices v] // top of head add [-30 20 -20] to [cat vertices v] // left ear add [30 20 -20] to [cat vertices v] // right ear add [-25 0 -30] to [cat vertices v] // left side add [25 0 -30] to [cat vertices v] // right side add [0 -20 -25] to [cat vertices v] // bottom // Define faces (triangles) add [1 2 4] to [cat faces v] // left side triangle add [1 3 5] to [cat faces v] // right side triangle add [2 4 6] to [cat faces v] // bottom left add [3 5 6] to [cat faces v] // bottom right
🎨 3D Rendering Engine
Create a complete rendering system:
// Main 3D render loop define 3d render clear set pen color to [#000000] set pen size to [2] // Rotate the cat change [rotation y v] by [2] // Process each face set [face index v] to [1] repeat (length of [cat faces v]) set [current face v] to (item (face index) of [cat faces v]) // Get the three vertices of this face set [v1 v] to (item (item 1 of (current face)) of [cat vertices v]) set [v2 v] to (item (item 2 of (current face)) of [cat vertices v]) set [v3 v] to (item (item 3 of (current face)) of [cat vertices v]) // Apply rotation and projection rotate and project vertex (v1) set [p1 x v] to (projected x) set [p1 y v] to (projected y) rotate and project vertex (v2) set [p2 x v] to (projected x) set [p2 y v] to (projected y) rotate and project vertex (v3) set [p3 x v] to (projected x) set [p3 y v] to (projected y) // Draw the triangle draw triangle (p1 x) (p1 y) (p2 x) (p2 y) (p3 x) (p3 y) change [face index v] by [1] end
🔄 Rotation Mathematics
Implement 3D rotation around Y-axis:
define rotate and project vertex (vertex) // Extract x, y, z from vertex string set [x v] to (item 1 of (vertex)) set [y v] to (item 2 of (vertex)) set [z v] to (item 3 of (vertex)) // Rotate around Y-axis set [cos angle v] to ([cos v] of (rotation y)) set [sin angle v] to ([sin v] of (rotation y)) set [rotated x v] to (((x) * (cos angle)) - ((z) * (sin angle))) set [rotated z v] to (((x) * (sin angle)) + ((z) * (cos angle))) set [rotated y v] to (y) // Project to 2D screen set [distance v] to [300] if <(rotated z) > [-250]> then set [projected x v] to (((rotated x) * (distance)) / ((rotated z) + (distance))) set [projected y v] to (((rotated y) * (distance)) / ((rotated z) + (distance))) else set [projected x v] to [0] set [projected y v] to [0] end
🎭 Advanced Features
Add realistic cat features:
// Cat animation system define animate cat // Tail swaying set [tail angle v] to (([sin v] of ((timer) * [180])) * [30]) // Ear twitching if <(pick random 1 to 100) < [5]> then set [ear twitch v] to [10] else if <(ear twitch) > [0]> then change [ear twitch v] by [-1] end end // Eye blinking if <(pick random 1 to 200) < [3]> then set [blink timer v] to [5] else if <(blink timer) > [0]> then change [blink timer v] by [-1] end end // Apply animations to vertices update cat model with animations
🎨 Texture and Shading
Add realistic appearance:
// Simple shading based on face normal define calculate face shading (face) // Calculate face normal vector set [normal x v] to [calculated normal x] set [normal y v] to [calculated normal y] set [normal z v] to [calculated normal z] // Light direction (from above-left) set [light x v] to [-1] set [light y v] to [1] set [light z v] to [-1] // Dot product for lighting intensity set [dot product v] to (((normal x) * (light x)) + ((normal y) * (light y)) + ((normal z) * (light z))) set [brightness v] to ((dot product) + [1]) / [2]) // Set pen color based on brightness set [gray value v] to ((brightness) * [255]) set pen color to (gray value)
💡 Pro Tips for 3D in Scratch
- Start simple: Begin with basic shapes before complex models
- Use lists efficiently: Store vertex and face data in organized lists
- Optimize rendering: Only draw faces facing the camera
- Add depth sorting: Draw far objects first for proper layering
- Use clones wisely: Create clones for repeated elements
This will give you a solid foundation for 3D modeling in Scratch! 🎯
3DModeler_Chris
Replied 2 hours later
@RaycastingExpert_Maya This is absolutely mind-blowing! 🤯
I never realized how much math goes into 3D graphics. The step-by-step breakdown makes it so much clearer. I’m starting with a simple cube first, then working up to the cat model.
Quick question: how do I handle collision detection with 3D objects?
CollisionDetector_Alex
Replied 4 hours later
@3DModeler_Chris Great question! Here’s 3D collision detection:
// 3D bounding box collision define check 3d collision (obj1) (obj2) // Get bounding boxes for both objects set [obj1 min x v] to (min x of (obj1)) set [obj1 max x v] to (max x of (obj1)) set [obj1 min y v] to (min y of (obj1)) set [obj1 max y v] to (max y of (obj1)) set [obj1 min z v] to (min z of (obj1)) set [obj1 max z v] to (max z of (obj1)) // Same for obj2... // Check overlap in all 3 dimensions if <<((obj1 max x) > (obj2 min x)) and ((obj1 min x) < (obj2 max x))> and <<((obj1 max y) > (obj2 min y)) and ((obj1 min y) < (obj2 max y))> and <((obj1 max z) > (obj2 min z)) and ((obj1 min z) < (obj2 max z))>>> then set [collision detected v] to [true] else set [collision detected v] to [false] end
For more precise collision, use sphere or mesh-based detection! 🎯
Vibelf_Community
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