readme update

README.md

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 # repa-shader
 Web component to render webgl shaders
+
+I'm planning to create a custom web component to easily embed fragment shaders to any website for a long time. Here it is finally - now that `webgpu` appeared, so I can move on to create something similar with that ;)
+
+I've tried to create `<repa-component>` to be [TWIGL](https://twigl.app/) compatible, supporting (and more-or-less autodetecting) _geekest_ mode and MRT as well. (But it supports only 300 es mode.)
+
+## Basic usage
+
+Include the `repa-shader.js` module in your HTML, then add your fragment shader code into a `<repa-shader>` element. That's it. Here's a simple red background:
+
+```html
+<script type="module" src="repa-shader.js"></script>
+<repa-shader width=400 height=400>
+void main() {
+  outColor = vec4(1.0, 0.0, 0.0, 1.0);
+}
+</repa-shader>
+```
+
+You can include your shader code in `<script type="x-shader/x-fragment">[your code here]</script>` tags as well, in this way you can override the default vertex shader too (using `x-shader/x-fragment` type).
+
+## &lt;repa-shader&gt;
+
+### Supported attributes
+
+- `width`, `height`: embedded canvas size
+- `alpha`: trasparent background
+- `snippets`: list of snippets to load
+- `snippet-prefix`: URL prefix of the snippets (`/snippets` by default)
+- `mouse`: mouse support
+- `orientation`: device orientation support
+- `mode`: shader mode
+  - `raw`: nothing is added, in this way you can embed version 200 shaders too
+  - `classic`: ~ twigl classic 300 es mode
+  - `geeker`: ~ twigl geeker 300 es mode
+  - `geekest`: ~ twigl geekest 300 es mode (`noise.glsl` snippet automatically included)
+- `render-target-count`: MRT target count
+- `src`: external fragment shader source
+- `fs-input`: id of the input/textarea element containing the shader source
+
+### Uniforms
+
+- `time` _float_, seconds from start (also available as `t`)
+- `frame` _float_, frame number from start (`f`)
+- `resolution` _vec2_, shader resolution (`r`)
+- `mouse` _vec3_, mouse position + button state (`m`)
+- `orientation` _vec3_, device orientation
+
+## &lt;repa-texture&gt;
+
+You can add textures using the `<repa-texture>` component included inside your `<repa-shader>`.
+
+### Attributes
+
+- `src`: texture source
+- `ref`: `id` of the referred texture element (like an existing image or video in the page)
+- `type`: texture type - sane autodetection available
+  - `image`
+  - `video`
+  - `webcam`
+  - `canvas`
+  - `audio`
+  - `shader` - other instance of `<repa-shader>`
+  - `raw` - content provided via JS or as JSON
+- `min-filter`, `mag-filter` (both set by `filter`): WebGL filtering
+- `wrap-s`, `wrap-t`, `wrap-r` (all set by `wrap`): WebGL wrapping
+- `format`: WebGL format
+- `internal-format`: WebGL internal format
+- `t3d`: 3d texture
+
+More about filtering/wrapping/formats at [MDN](https://developer.mozilla.org/en-US/docs/Web/API/WebGLRenderingContext/texImage2D)
+
+## Examples
+
+Check the [demo](demo) folder for more detailed examples.