Shadow Catcher Script

scripts/esm/shadow-catcher.mjs

@@ -0,0 +1,108 @@
+import {
+    Script,
+    Entity,
+    StandardMaterial,
+    BLEND_NORMAL,
+    SHADOW_VSM16,
+    SHADOWUPDATE_REALTIME,
+    CHUNKAPI_1_70,
+    Vec2
+} from 'playcanvas';
+
+/** @import { AppBase, Entity, Light } from 'playcanvas' */
+
+const endPS = `
+    litArgs_opacity = mix(light0_shadowIntensity, 0.0, shadow0);
+    gl_FragColor.rgb = vec3(0.0);
+  `;
+
+/**
+ * This script generates a simple shadow plane for any render-able objects within
+ * it's hierarchy. This means you can attach it to a parent entity and quickly get
+ * visible ground plane, which helps to stage models.
+ */
+class ShadowCatcherScript extends Script {
+    /**
+     * The shadow distance of the shadow catcher light.
+     * @type {number}
+     * @attribute
+     */
+    shadowDistance = 16;
+
+    /**
+     * The VSM blur size of the shadow catcher light.
+     * @type {number}
+     * @attribute
+     */
+    blurSize = 32;
+
+    /**
+     * The size of the shadow catcher.
+     * @type {Vec2}
+     * @attribute
+     */
+    size = new Vec2(1, 1);
+
+    /**
+     * @type {pc.Entity}
+     */
+    _plane;
+
+    /**
+     * @type {pc.Entity}
+     */
+    _light;
+
+    initialize() {
+        // create shadow catcher material
+        const material = new StandardMaterial();
+        material.useSkybox = false;
+        material.blendType = BLEND_NORMAL;
+        material.chunks = {
+            APIVersion: CHUNKAPI_1_70,
+            endPS: endPS
+        };
+        material.update();
+
+        // create shadow catcher geometry
+        this._plane = new Entity('ShadowPlane');
+        this._plane.addComponent('render', {
+            type: 'plane',
+            castShadows: false,
+            material
+        });
+        this._plane.setLocalScale(this.size.x, 1, this.size.y);
+
+        // create shadow catcher light
+        this._light = new Entity('ShadowLight');
+        this._light.addComponent('light', {
+            type: 'directional',
+            castShadows: true,
+            normalOffsetBias: 0,
+            shadowBias: 0,
+            shadowDistance: this.shadowDistance,
+            shadowResolution: 1024,
+            shadowType: SHADOW_VSM16,
+            shadowUpdateMode: SHADOWUPDATE_REALTIME,
+            vsmBlurSize: this.blurSize,
+            shadowIntensity: 1,
+            intensity: 0
+        });
+
+        this.app.root.addChild(this._plane);
+        this.app.root.addChild(this._light);
+
+        this.on('destroy', () => {
+            this._plane.destroy();
+            this._light.destroy();
+            material.destroy();
+        });
+    }
+
+    update() {
+        this._plane.setLocalScale(this.size.x, 1, this.size.y ?? this.size.x);
+        this._light.light.vsmBlurSize = this.blurSize;
+    }
+}
+
+export { ShadowCatcherScript };