Allow texture and specularMaterial to coexist, explicitly defaulting _hasSetAmbient to false

[inaridarkfox4231]

Setting _hasSetAmbient to false when doing fill() and texture() will make that look the default. Coexistence is possible by calling ambientMaterial() afterwards.
Stop texture() from disabling Materials such as specular. Conversely, it also prevents specularMaterial() etc. from destroying the texture. Allow both to coexist.

Resolves #6133

Changes:

Make _hasSetAmbient false when you call fill().
Set _hasSetAmbient to false when you call texture(). Also, stop setting _useSpecularMaterial and _useEmissiveMaterial to false.
Prevent _tex from being null when calling ambientMaterial(), specularMaterial(), emissiveMaterial().

Screenshots of the change:

function setup() {
  createCanvas(400, 400, WEBGL);

  const tex = createGraphics(256, 256);
  tex.noStroke();
  for(let i=0; i<256; i++){
    tex.fill(i, i, 255);
    tex.rect(0, i, 256, 1);
  }
  noStroke();

  lights();

  texture(tex);
  specularMaterial(128); // turns texture to null.

  shininess(400);
  plane(400);
}

latest version output / expected output

PR Checklist

• npm run lint passes
• Inline documentation is included / updated
• Unit tests are included / updated

[inaridarkfox4231]

Unit test seems fine. Below, I will add screenshots of the change, unit tests, references, and examples.

[inaridarkfox4231]

In Three.js, specular can coexist naturally with texture as part of a material called phongMaterial. It seems to be a natural process after all, so let's incorporate it into p5.js.

[inaridarkfox4231]

Unit test completed. Next, I will add the contents that reflect this specification change to each reference of fill(), texture(), and ambientMaterial().

[davepagurek]

Sorry for the delay, I've been recovering the past few days! I think this is a good change, would you be interested in reopening this?

[davepagurek]

Maybe instead of mentioning the ambient term here, we could phrase it like: fill sets all reflective material colors to the specified color, but if you want to set them individually, use speculatMaterial() and ambientMaterial().

[inaridarkfox4231]

Regarding the ambientMaterial flag, I decided not to set it to false. I will close this pull request once. I will launch a pull request on another topic (about omitting processing to null _tex), so please review it.
If I don't call ambientMaterial(), the color won't fade, so that's fine. thank you.

[davepagurek]

If we're just doing assertions on one pixel, maybe we can do tex.background() instead of doing a gradient here?

[inaridarkfox4231]

I will recreate it when I create a unit test in a new pull request. Later I realized that textures can be monochromatic. excuse me. I will do so when I recreate it.