* add unbiased mode to the MSAA render pass.

* clearer code.

* better comment.

* cleanup code.  fix bug of using "camera", instead of "this.camera"

* fix more places were "camera" is used instad of "this.camera" -- it worked because example declared "camera" as a global.

* reduce light intensity.

* add PerspectiveCamera.clearViewOffset() per @mrdoob's recommendation.

Add high quality rand() function to common.glsl and an example to show off the noise textures. (#8603)

* create procedural glsl and an example to show off the noise textures.

* add to files.js

* adopt noise procedural in PMREMGenerator.

* fix page title per @arose's suggestion.

* more adoption of procedural.glsl

* remove procedural.glsl, add a single line to common.glsl.  Update other files as needed.

* cleanup shaders to use common.glsl

* tabify.

* avoid collapsing into a single function - @WestLangley recommendations

* more adoption of tabs.

* fix tabs.

* working on depth texture

* working on depth texture

* support depth texture in webgl1 and webgl2

* fix comments

* reset build to avoid diff noise

* add check for webgl2 context

* fix depth texture example

* animation for example

* add file

* add depthTexture to WebGLRenderTarget

* ensure depth format returns correct GL parmaeter

* use null for initial depthTexture value

* add some commented out code

* special purpose materials.

* rename example from special_purpose -> channels.  Add camera controls.

* minor polish to webgl_materials_channels.

* add standard material with displacement, normal and ao to show contract with normal and depth materials.

* fix orthographic camera near/far bounds.

* remove double add of material_channels example.

* Implemented user-defined clipping planes.

* Renderer: Minor documentation update.

* Implements object-level clipping.

* Renderer: Minor cosmetic changes.

* Fixed lethal typo in normal shader.

* Let shadows respect .side of object's material.

* Fixed Plane.applyMatrix4.

- Scale denormalized but did not scale the position
- Projection is not supported (solved by documentation)
- Removed unnecessary copying to make up for the normalization
- Still arguably too heavy

* Added custom clipping example.

* Clipping: Fixed transition to disabled state.

* Improved custom clipping example.

- GUI dependency of volume visualization on Enabled state
- Larger radius for cylindrical global clipping area

* No .matrixAutoUpdate = false in clipping example.

* Let ShadowMap check renderer.localClippingEnabled.

* Added a simplified clipping example.

adds both new spotlight examples