Bug 1908624 Comment 6 Edit History

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Original comment by
on 
From github: https://github.com/niels747/2D-Weather-Sandbox/issues/99#issuecomment-1817703743
> Found this little nugget.
> > WebGL warning: readPixels: Format and type RGBA_INTEGER/<enum 0x1400> incompatible with this RGBA8I attachment. This framebuffer requires either RGBA_INTEGER/INT or getParameter(IMPLEMENTATION_COLOR_READ_FORMAT/_TYPE) RGBA_INTEGER/INT.
> 
> For some reason this fixes it. It probably blows up memory usage.
> ```
> gl.readBuffer(gl.COLOR_ATTACHMENT2);
> var wallTextureValues = new Int32Array(4 * sim_res_y);
> gl.readPixels(simXpos, 0, 1, sim_res_y, gl.RGBA_INTEGER, gl.INT, wallTextureValues); // read a vertical column of cells
> ```
> Using Int32Array and gl.INT where ever wallTextureValues is populated fixes both this issue, and the unreported issue of weather stations not working on Firefox. No side effects on Chrome.
> 
> Why? I don't know.

So this is an attempt to call ReadPixels(RGBA_INTEGER,BYTE) from a RGBAI8 source. The only spec-guaranteed way to read from an "int-ish" format is `RGBA_INTEGER/INT`, but a driver *may* offer some other pair, that authors may query via `getParameter(IMPLEMENTATION_COLOR_READ_FORMAT/_TYPE)`.
**So that's why switching to `gl.RGBA_INTEGER, gl.INT` works: It is a requirement for portability!**


Authors *may choose* to check the alternative, which *might* happen to be supported by a driver:
```
const alternative = {
  format: gl.getParameter(gl.IMPLEMENTATION_COLOR_READ_FORMAT),
  type: gl.getParameter(gl.IMPLEMENTATION_COLOR_READ_TYPE),
};
if (alternative.format == gl.RGBA_INTEGER &&
   alternative.type = gl.BYTE) {
  // the existing readPixels(RGBA_INTEGER,BYTE) code
} else {
  // readPixels(gl.RGBA_INTEGER, gl.INT) code
}
```
Revision 1 by
on 
From github: https://github.com/niels747/2D-Weather-Sandbox/issues/99#issuecomment-1817703743
> Found this little nugget.
> > WebGL warning: readPixels: Format and type RGBA_INTEGER/<enum 0x1400> incompatible with this RGBA8I attachment. This framebuffer requires either RGBA_INTEGER/INT or getParameter(IMPLEMENTATION_COLOR_READ_FORMAT/_TYPE) RGBA_INTEGER/INT.
> 
> For some reason this fixes it. It probably blows up memory usage.
> ```
> gl.readBuffer(gl.COLOR_ATTACHMENT2);
> var wallTextureValues = new Int32Array(4 * sim_res_y);
> gl.readPixels(simXpos, 0, 1, sim_res_y, gl.RGBA_INTEGER, gl.INT, wallTextureValues); // read a vertical column of cells
> ```
> Using Int32Array and gl.INT where ever wallTextureValues is populated fixes both this issue, and the unreported issue of weather stations not working on Firefox. No side effects on Chrome.
> 
> Why? I don't know.

So this is an attempt to call ReadPixels(RGBA_INTEGER,BYTE) from a RGBAI8 source. The only spec-guaranteed way to read from an "int-ish" format is `RGBA_INTEGER/INT`, but a driver *may* offer some other pair, that authors may query via `getParameter(IMPLEMENTATION_COLOR_READ_FORMAT/_TYPE)`.
**So that's why switching to `gl.RGBA_INTEGER, gl.INT` works: It is the only combo that is guaranteed to work on all computers!**


Authors *may choose* to check the alternative, which *might* happen to be supported by a driver:
```
const alternative = {
  format: gl.getParameter(gl.IMPLEMENTATION_COLOR_READ_FORMAT),
  type: gl.getParameter(gl.IMPLEMENTATION_COLOR_READ_TYPE),
};
if (alternative.format == gl.RGBA_INTEGER &&
   alternative.type = gl.BYTE) {
  // the existing readPixels(RGBA_INTEGER,BYTE) code
} else {
  // readPixels(gl.RGBA_INTEGER, gl.INT) code
}
```
Revision 2 by
on 
From github: https://github.com/niels747/2D-Weather-Sandbox/issues/99#issuecomment-1817703743
> Found this little nugget.
> > WebGL warning: readPixels: Format and type RGBA_INTEGER/<enum 0x1400> incompatible with this RGBA8I attachment. This framebuffer requires either RGBA_INTEGER/INT or getParameter(IMPLEMENTATION_COLOR_READ_FORMAT/_TYPE) RGBA_INTEGER/INT.
> 
> For some reason this fixes it. It probably blows up memory usage.
> ```
> gl.readBuffer(gl.COLOR_ATTACHMENT2);
> var wallTextureValues = new Int32Array(4 * sim_res_y);
> gl.readPixels(simXpos, 0, 1, sim_res_y, gl.RGBA_INTEGER, gl.INT, wallTextureValues); // read a vertical column of cells
> ```
> Using Int32Array and gl.INT where ever wallTextureValues is populated fixes both this issue, and the unreported issue of weather stations not working on Firefox. No side effects on Chrome.
> 
> Why? I don't know.

So this is an attempt to call ReadPixels(RGBA_INTEGER,BYTE) from a RGBAI8 source. The only spec-guaranteed way to read from an "int-ish" format is `RGBA_INTEGER/INT`, but a driver *may* offer some other pair, that authors may query via `getParameter(IMPLEMENTATION_COLOR_READ_FORMAT/_TYPE)`.
**So that's why switching to `gl.RGBA_INTEGER, gl.INT` works: It is the only combo that is guaranteed to work on all computers!**


Authors *may choose* to check the alternative, which *might* happen to be supported by a driver:
```
const alternative = {
  format: gl.getParameter(gl.IMPLEMENTATION_COLOR_READ_FORMAT),
  type: gl.getParameter(gl.IMPLEMENTATION_COLOR_READ_TYPE),
};
if (alternative.format == gl.RGBA_INTEGER &&
   alternative.type == gl.BYTE) {
  // the existing readPixels(RGBA_INTEGER,BYTE) code
} else {
  // readPixels(gl.RGBA_INTEGER, gl.INT) code
}
```

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