Small fixes and improvements.

src/core/IMaterial.ts

         [key: string]: any
     }
 
+    /**
+     * Force a depth value in GBuffer.
+     * This is useful to force center values like 0 to the depth.
+     */
+    forcedLinearDepth?: number
 
     // todo: move these to respective plugins
 

src/core/material/IMaterialUi.ts

                     property: [material, 'depthWrite'],
                     onChange: (ev)=>material.setDirty({uiChangeEvent: ev}),
                 },
+                {
+                    type: 'checkbox',
+                    property: [material, 'colorWrite'],
+                    onChange: (ev)=>material.setDirty({uiChangeEvent: ev}),
+                },
                 {
                     type: 'slider',
                     bounds: [0, 1],

src/materials/MaterialExtender.ts

     static CacheKeyForExtension(material: IMaterial, materialExtension: MaterialExtension): string {
         let r = ''
         if (materialExtension.computeCacheKey) r += getOrCall(materialExtension.computeCacheKey, material)
+        else r += materialExtension.uuid
         if (materialExtension.extraDefines) r += Object.values(materialExtension.extraDefines).map(v=>getOrCall(v) ?? '').join('')
         return r
     }
         if (customMaterialExtensions)
             for (const ext of customMaterialExtensions) {
                 if (!ext.isCompatible || !ext.isCompatible(material) || material.materialExtensions.includes(ext)) continue
-                else exts.push(ext)
+                exts.push(ext)
                 if (!ext.uuid) ext.uuid = generateUUID()
                 if (!ext.__setDirty) ext.__setDirty = ()=>{
                     if (!ext.updateVersion) ext.updateVersion = 0
                 if (!ext.setDirty) ext.setDirty = ext.__setDirty
             }
 
+        if (!exts.length) return []
+
         material.materialExtensions = [...material.materialExtensions || [], ...exts]
             .sort((a, b)=>(b.priority || 0) - (a.priority || 0))
 
             (material as any).__ext_afterRenderListen = true
             material.addEventListener('afterRender', materialAfterRender)
         }
+
+        material.needsUpdate = true
         return exts
     }
 

src/materials/MaterialExtension.ts

      * Check three.js docs for more info.
      * Value can be a string or a function that returns a string
      * This will only be checked if `material.needsUpdate` is `true`, not on every render.
+     * Note: extension might never be registered if an empty string is returned.
      */
     computeCacheKey?: string | ((material: IMaterial) => string)
 

src/plugins/pipeline/GBufferPlugin.ts

             ['USE_DISPLACEMENTMAP']: this.uniforms.displacementMap.value ? 1 : undefined,
             ['DISPLACEMENTMAP_UV']: this.uniforms.displacementMap.value ? 'uv' : undefined, // todo use getChannel, see WebGLPrograms.js
             ['ALPHA_I_RGBA_PACKING']: material.userData.ALPHA_I_RGBA_PACKING ? 1 : undefined,
-            ['FORCED_LINEAR_DEPTH']: material.userData.forcedLinearDepth ?? undefined,
+            ['FORCED_LINEAR_DEPTH']: material.userData.forcedLinearDepth ?? undefined, // todo add to DepthBufferPlugin as well.
         }, material)
 
         // todo: do the same in DepthBufferPlugin and NormalBufferPlugin

src/three/Threejs.ts

 export {EffectComposer} from 'three/examples/jsm/postprocessing/EffectComposer.js'
 
 export {OrbitControls} from 'three/examples/jsm/controls/OrbitControls.js'
+export * from 'three/examples/jsm/utils/BufferGeometryUtils.js'

src/utils/shader-helpers.ts

 const warnEnabled = true
-
+const errorStr1 = 'shaderReplaceString: str must be passed if str is a RegExp and append/prepend is true'
 /**
  * Replace a string in a shader function with added options to prepend, append, show warning when not found, and replace all occurrences.
  * @param shader - shader code
  * @param replaceAll - replace all occurrences
  * @param prepend - prepend new string to old string
  * @param append - append new string to old string
+ * @param _str - optional string to use for replacement. This must be passed if str is a RegExp and append/prepend is true
  */
 export function shaderReplaceString(shader: string, str: string|RegExp, newStr: string, {
     replaceAll = false,
     prepend = false,
     append = false,
+    str: _str = undefined as string|undefined,
 } = {}) {
     // todo: use safeReplaceString from ts-browser-helpers
+    const isStr = typeof str === 'string'
     if (warnEnabled /* && ThreeViewer.ViewerDebugging */) {
-        if (typeof str === 'string' ? !shader.includes(str) : !str.test(shader)) {
+        if (isStr ? !shader.includes(str) : !str.test(shader)) {
             console.error(`${str} not found in shader`)
             return shader
         }
     }
     let s = newStr
+    _str = _str ?? (isStr ? str : undefined)
     if (prepend) {
-        s = newStr + str
+        if (typeof _str !== 'string') throw new Error(errorStr1)
+        s = newStr + _str
     } else if (append) {
-        s = str + newStr
+        if (typeof _str !== 'string') throw new Error(errorStr1)
+        s = _str + newStr
     }
     return replaceAll ? shader.replaceAll(str, s) : shader.replace(str, s)
 }