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dev-docs/RFCs/v7.x/post-process-effect-rfc.md

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+# RFC: Post-processing Effect Rendering
+
+* **Authors**: Jian Huang
+* **Date**: May. 2019
+* **Status**: For Review
+
+## Abstract
+Post-processing effect rendering is part of deck.gl effect rendering pipeline, focusing on screen space pixel manipulation by using ping-pong technique.
+
+## Design
+
+A post-processing effect is created from `PostProcessEffect` class and Shader module.
+```js
+import {brightnessContrast} from @luma.gl/effects;
+import {PostProcessEffect} from @deck.gl/core;
+
+const postProcessEffect = new PostProcessEffect(brightnessContrast, {
+  brightness: 0.5,
+  contrast: 0.5
+});
+```
+
+### API
+
+`PostProcessEffect` class is the public interface to create post-processing effects, it only has two params.
+* `module`(Object): GLSL shader code and default uniforms for rendering
+* `props`(Object): parameters to tune effects
+
+`ScreenPass` class is the internal interface to handle the rendering of one pass, it is created by PostProcessEffect dynamically from shader module.
+* `inputBuffer`(Object): frame buffer object as input data
+* `outputBuffer`(Object): frame buffer object as out
+
+### Shader Module
+`@luma.gl/effects` lib will host all the post-processing effect shader modules, currently most of them are sitting in `@luma.gl/glfx`. A typical shader module defines `name`, `uniforms` and `Shader Func`.
+```js
+const fs = `\  
+uniform float brightness;  
+uniform float contrast;  
+
+vec4 brightnessContrast_filterColor(vec4 color, vec2 texSize, vec2 texCoords) {  
+ return brightnessContrast_filterColor(color);
+}  
+`;  
+
+const uniforms = {  
+  brightness: {value: 0, min: -1, max: 1},  
+  contrast: {value: 0, min: -1, max: 1}  
+};  
+
+export default {  
+  name: 'brightnessContrast',  
+  uniforms,  
+  fs,  
+  passes: [{filter: true}]  
+};
+```
+### Workflow
+<pre>Layers -----> Framebuffer
+                       \
+                        DeckRenderer -----> Screen
+                       /
+Effects -----> ScreenPasses</pre>
+
+## Limitation
+* Only support postprocessing on the entire screen, not per viewport.
+* Only support pure screen space effects from luma.gl