Add factories for finer color management

src/drawables/shapes/meta-circle-factory.ts

@@ -0,0 +1,62 @@
+import { mat2d, vec2, vec3, vec4 } from 'gl-matrix';
+import { codeForColorAccess } from '../../helper/code-for-color-access';
+import { DrawableDescriptor } from '../drawable-descriptor';
+import { EmptyDrawable } from '../empty-drawable';
+
+/**
+ * @category Drawable
+ */
+class MetaCircleBase extends EmptyDrawable {
+  constructor(public center: vec2, public radius: number) {
+    super();
+  }
+}
+
+/**
+ * @category Drawable
+ */
+export const MetaCircleFactory = (color: vec3 | vec4 | number): typeof MetaCircleBase => {
+  class MetaCircle extends MetaCircleBase {
+    public static descriptor: DrawableDescriptor = {
+      sdf: {
+        shader: `
+          uniform vec2 metaCircleCenters[META_CIRCLE_COUNT];
+          uniform float metaCircleRadii[META_CIRCLE_COUNT];
+
+          const float k = 32.0;
+          float metaCircleMinDistance(vec2 target, out vec4 color) {
+            color = ${codeForColorAccess(color)};
+            float res = 0.0;
+            for (int i = 0; i < META_CIRCLE_COUNT; i++) {
+              float dist = distance(metaCircleCenters[i], target) - metaCircleRadii[i];
+              res += exp2(-k * dist);
+            }
+
+            return -log2(res) / k;
+          }
+        `,
+        distanceFunctionName: 'metaCircleMinDistance',
+      },
+      propertyUniformMapping: {
+        center: 'metaCircleCenters',
+        radius: 'metaCircleRadii',
+      },
+      uniformCountMacroName: 'META_CIRCLE_COUNT',
+      shaderCombinationSteps: [0, 1, 2, 3, 8, 16],
+      empty: new MetaCircle(vec2.create(), 0),
+    };
+
+    public minDistance(target: vec2): number {
+      return vec2.dist(this.center, target) - this.radius * 2;
+    }
+
+    protected getObjectToSerialize(transform2d: mat2d, transform1d: number): any {
+      return {
+        center: vec2.transformMat2d(vec2.create(), this.center, transform2d),
+        radius: this.radius * transform1d,
+      };
+    }
+  }
+
+  return MetaCircle;
+};