BA Kolloquium

Lazy Model Generation

Bachlor Theses topic
by Maarten Behn

---

Idea: extend Paper from Paul Merrell

---

---

Model Synthesis Algorithm

1. Give every node every value
2. Pick a node and choose one Value
3. Check all other nodes values if they can still exist
4. Go to 2
5. Every node has been picked ⇒ done

$O(n^2\cdot m)n=|Nodes|m=|Values|$

---

Problems with Model Synthesis

• No partial regeneration when rules change
• Very hard to write your own rules

---

Shader Graph / Blender Geometry Nodes / etc.

Every possible configuration is valid?

---

My Idea

---

Valid solutions

---

Dependency

---

calculate path to all dependencies once in template.

---

Value types

• Number (Integer)

• Number Set

• Position (Vector3)

• Position Set

  • All Positions in Volume on a
    • Grid
    • Poissons sampling

• Build

---

Amount is defined

• n global
• n per other node
• by other node

Value is defined

• at Template generation
• callback at evaluation (Hook)
• by other node

---

Implementation

let builder = Builder::new()  
	.number_range(<Name>, |b|{b  
		.ammount(OneGlobal(<Name>))  
		.value(Const(3..=8))  
		.depends_on(<Name>)  
		.knows(<Name>)  
	})  
	  
	.pos(<Name>, |b|{b  
		.ammount(OnePer(<Name>))  
		.value(Hook)  
	})  
	  
let template = builder.build();  

---

let collapser = template.get_collasper();  
  
for hook in collapser {  
    match hook {  
		NumberRangeHook { index, name } => {  
			let value = collapser.get_dependent(index, <OtherName>)   
			  
		},  
		PosSetHook { name } => {  
			match name {  
				<Name> => {  
				  
				},  
				<Name> => {  
				  
				}  
			}  
		},  
		PosHook { name } => {  
			  
		},  
		Build { name } => {  
			  
		},  
		Undo { name } => {  
			  
		},  
		None => {},  
	}   
}  
  

---

Generating Geometry

• Naive: passing a valid solution
• OR: generating geometry while searching for a valid solution
  • more complex
  • interactive
  • solution search can run in the background
  • system can be used for LOD based generation

---

---

Voxel DAG Raytracer

---

Keep partially collapsed versions on the GPU for fast undo.

---

Sources

https://paulmerrell.org
https://github.com/mxgmn/WaveFunctionCollapse
https://unity.com/de/features/shader-graph