Guiding vectors #140

davepagurek · 2018-08-11T16:37:37Z

This adds a cost function which only looks at the structure of shapes.

How it works

You specify some bezier curves (visualized in white on top of everything)
For any given point in space, the guiding vector for that point is equal to the slope at the closest point on any of the specified bezier curves
When a new node is added (we specifically don't look at GeometryNodes), the vector from the node's origin to its parent node's origin is compared to the target vector at that location. The cost is zero if it is exactly aligned.

Good examples

Bad examples

This behaviour, while correct, is probably unexpected. The tree grows along the extrapolated vector field lines, but they diverge from the original curve. This can maybe be addressed by adding a falloff function of some kind so that the cost goes up the farther away from a target curve you get, regardless of orientation.

Other refactors done in the process

Cost functions are classes now. Hopefully that makes them more readable, as they can refactor pieces into private methods. (This also enables them to expose additional methods for visualization purposes.)

Note on Bezier curves

Right now, a bezier curve is defined by four points: The first endpoint, the first control point, the second control point, and the final endpoint.

We can maybe add a UI later to adjust these control points. But it's maybe not too bad leaving this as a text input since at least artists are aware of what the control points are from having used Illustrator and conventional 3D modelling programs.

davepagurek · 2018-08-11T16:43:07Z

package.json

@@ -30,16 +30,19 @@
    "lint": "tslint -t stylish --project \"tsconfig.json\"",
    "test": "npm run test-only",
    "test-only": "jest --coverage",
-    "watch": "tsc -w -p tsconfig.build.json"
+    "watch": "tsc -w -p tsconfig.build.json",
+    "webpack": "webpack"


I added this because I had been doing some development in the graphics lab, which has npm but not yarn. Yarn automatically translates rules like this, but npm doesn't.

davepagurek · 2018-08-11T16:44:44Z

Also: the new cost function classes for FillVolume and ForcePoints are unchanged from before, but now structured as classes with private methods instead of a giant function that initially defines sub-functions. The actual code there hasn't changed.

armcburney · 2018-08-12T09:46:37Z

I like the idea about potentially having a UI for the adjusting the control points 👍

armcburney · 2018-08-12T09:47:03Z

.gitignore

@@ -19,3 +19,5 @@ src/**/*.js
 src/**/*.js.map
 tests/**/*.js
 tests/**/*.js.map
+
+*.swp


vim 👎 😂

armcburney · 2018-08-12T09:48:46Z

package.json

  },
  "author": "",
  "license": "MIT",
  "dependencies": {
+    "@types/bezier-js": "^0.0.7",


How production ready is bezier-js? Are there any concerns about using this library?

Seems pretty legit, the things documented here http://pomax.github.io/bezierjs/ don't seem to have significant active issues (issues are mostly feature requests)

armcburney · 2018-08-12T09:50:30Z

src/armature/FillVolume.ts

+/**
+ * Creates a cost function based on how much of a target volume a shape fills.
+ */
+export class FillVolume {


Could we have an abstract base class or interface for Cost, with methods getCost here?

I see that you have the CostFn interface, could you please specify that this class is implementing it?

armcburney · 2018-08-12T09:53:01Z

src/armature/FillVolume.ts

+                    grid,
+                    (point: string) =>
+                        // If this point was in the target region, reduce the cost
+                        (incrementalCost +=


is this the autoformatter's doing? 🤕 lol

armcburney · 2018-08-12T09:58:09Z

src/armature/GuidingVectors.ts

+     * @param {number} step The space between field lines
+     * @returns {Float32Array} A buffer of vertices for the vector field lines.
+     */
+    public generateVectorField(radius: number = 3, step: number = 0.5): Float32Array {


This breaks the Dependency Inversion Principle if this class is supposed to implement the same CostFn interface. Do you think we could refactor this somehow?

I'm not sure what the best way to do this would be. From SOSMC's point of view, it only uses the getCost method, so it only has access to the CostFn interface. However, there will inevitably be different things that we want to visualize for each type of cost function so I'm not sure how to get them into the same interface for absolutely everything, so exposing extra methods that SOSMC can't see but that we can still pass to the renderer seemed like a decent compromise to me. I'm open to better suggestions though

armcburney · 2018-08-12T09:58:28Z

src/armature/GuidingVectors.ts

+     *
+     * @returns {Float32Array[]} A vertex buffer for each curve.
+     */
+    public generateGuidingCurve(): Float32Array[] {


Same comment here about the Dependency Inversion Principle

armcburney · 2018-08-12T10:06:23Z

src/examples/generation.ts

    Renderer,
    RGBColor,
    Shape
 } from '../calder';

+// tslint:disable-next-line:import-name
+import Bezier = require('bezier-js');


Are we going to require the user imports this library in their calder code, or could we abstract this?

I mean, I guess it matters less since we're research focused now, and not user-focused.

we could always provide our own wrapper, but yeah for now they do

armcburney

Nice work Dave! This is great! 🎉

davepagurek · 2018-08-13T14:42:38Z

re: control points UI, if we decide this is the base cost function we want to go with, then we could start out with a UI where you have maybe xyz sliders for each point and you see updates in real time, and then it shows a corresponding BezierJs.Bezier constructor for you to paste in to avoid directly editing the code.

davepagurek and others added 8 commits August 11, 2018 12:18

Make cost functions into classes

c2f892b

Add guiding vector cost

2b8d5e1

Add bezier curves

e8768c0

Visualize vector field

aebf25a

Colour the vector field

4593860

Clean up, visualize curve

6217939

Fix format

4836fcc

Fix formatting

aca2ea7

davepagurek commented Aug 11, 2018

View reviewed changes

armcburney reviewed Aug 12, 2018

View reviewed changes

armcburney approved these changes Aug 12, 2018

View reviewed changes

Explicitly say implements CostFn

97e9a57

davepagurek merged commit 5188f34 into master Aug 19, 2018

davepagurek deleted the cost-fn-tests branch August 19, 2018 13:12

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Guiding vectors #140

Guiding vectors #140

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davepagurek commented Aug 13, 2018

Guiding vectors #140

Guiding vectors #140

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davepagurek commented Aug 11, 2018

How it works

Good examples

Bad examples

Other refactors done in the process

Note on Bezier curves

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davepagurek commented Aug 13, 2018