# Passing data to shader using texture
**URL:** https://discourse.processing.org/t/passing-data-to-shader-using-texture/44446
**Category:** Coding Questions
**Created:** [May 18, 2024, 10:44pm UTC](https://discourse.processing.org/t/passing-data-to-shader-using-texture/44446 "2024-05-18T22:44:45Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@ekez](https://discourse.processing.org/u/ekez)
#### Post date: [May 18, 2024, 10:44pm UTC](https://discourse.processing.org/t/passing-data-to-shader-using-texture/44446/1 "2024-05-18T22:44:46Z")
Hi there,
I want to pass timeseries data into a shader. Because the data is potentially quite long, I am trying to do so by writing the data to a texture, then passing the texture to my shader. I’m finding the texture doesn’t get passed into the shader correctly.
Here’s a [small sketch](https://editor.p5js.org/0xekez/sketches/SiOFgeVlG) showing this.
Here’s a class I’ve written to manage the texture.
```auto
class TextureArray {
constructor(length, gl) {
this.data = new Float32Array(length)
this.gl = gl
const texture = gl.createTexture()
gl.bindTexture(gl.TEXTURE_2D, texture)
gl.texImage2D(gl.TEXTURE_2D, 0, gl.R32F, this.data.length, 1, 0, gl.RED, gl.FLOAT, this.data)
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE)
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE)
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR)
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR)
this.texture = texture
}
push(x) {
for (let i = this.data.length - 1; i > 0; i -= 1) {
this.data[i] = this.data[i - 1]
}
this.data[0] = x
const gl = this.gl
gl.bindTexture(gl.TEXTURE_2D, this.texture)
gl.texSubImage2D(gl.TEXTURE_2D, 0, 0, 0, this.data.length, 1, gl.RED, gl.FLOAT, this.data)
}
}
```
Then, I pass this texture to the shader using the following code:
```auto
s = createShader(vs, fs)
shader(s)
const uniform = s.uniforms["meow"]
const location = uniform.location
s.useProgram()
gl.activeTexture(gl.TEXTURE0 + uniform.samplerIndex)
gl.bindTexture(gl.TEXTURE_2D, a.texture)
gl.uniform1i(location, uniform.samplerIndex)
```
However, in the shader the meow texture only contains zero values (no matter how I initialize the input texture array). I was wondering if anyone here sees something wrong with the code. Thanks!
---
### Author:  [@davepagurek](https://discourse.processing.org/u/davepagurek)
#### Post date: [July 26, 2024, 12:15pm UTC](https://discourse.processing.org/t/passing-data-to-shader-using-texture/44446/2 "2024-07-26T12:15:06Z")
Try using a p5.Framebuffer to create your textures (updating their pixels array) and then using that for data. I have an example of that here, passing a bunch of points into a shader: [2.5d blob test - OpenProcessing](https://openprocessing.org/sketch/2308573)
---
### Author:  [@scudly](https://discourse.processing.org/u/scudly)
#### Post date: [October 25, 2024, 12:13am UTC](https://discourse.processing.org/t/passing-data-to-shader-using-texture/44446/3 "2024-10-25T00:13:27Z")
Note that because p5 pre-multiplies textures by their alpha value, if you try to pass in data on all four channels, the alpha will wipe out the other values. You can disable this with
```auto
let gl = myFB.gl;
gl.pixelStorei(gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, false);
myFB.updatePixels();
```
@davepagurek, perhaps we could add an optional parameter to `updatePixels()` to temporarily disable the alpha pre-multiply to better support data textures.