Materialupdate (#17701)

https://forum.babylonjs.com/t/blend-not-working-in-latest-build/62152

Author: sebavan

packages/dev/core/src/Engines/constants.ts

@@ -15,7 +15,7 @@ export class Constants {
      */
     public static readonly ALPHA_COMBINE = 2;
     /**
-     * Defines that alpha blending is COLOR=(1 - SRC) * DEST, ALPHA=SRC_ALPHA - DEST_ALPHA
+     * Defines that alpha blending is COLOR=(1 - SRC) * DEST, ALPHA=SRC_ALPHA + DEST_ALPHA
      * Subtracts source from destination, leading to darker results
      * */
     public static readonly ALPHA_SUBTRACT = 3;

packages/dev/core/src/Materials/material.ts

@@ -612,7 +612,7 @@ export class Material implements IAnimatable, IClipPlanesHolder {
      * | 0 | ALPHA_DISABLE |  |
      * | 1 | ALPHA_ADD | Defines that alpha blending is COLOR=SRC_ALPHA * SRC + DEST, ALPHA=DEST_ALPHA |
      * | 2 | ALPHA_COMBINE | Defines that alpha blending is COLOR=SRC_ALPHA * SRC + (1 - SRC_ALPHA) * DEST, ALPHA=SRC_ALPHA + DEST_ALPHA |
-     * | 3 | ALPHA_SUBTRACT | Defines that alpha blending is COLOR=(1 - SRC) * DEST, ALPHA=SRC_ALPHA - DEST_ALPHA |
+     * | 3 | ALPHA_SUBTRACT | Defines that alpha blending is COLOR=(1 - SRC) * DEST, ALPHA=SRC_ALPHA + DEST_ALPHA |
      * | 4 | ALPHA_MULTIPLY | Defines that alpha blending is COLOR=DEST * SRC, ALPHA=SRC_ALPHA + DEST_ALPHA |
      * | 5 | ALPHA_MAXIMIZED | Defines that alpha blending is COLOR=SRC_ALPHA * SRC + (1 - SRC) * DEST, ALPHA=SRC_ALPHA + DEST_ALPHA |
      * | 6 | ALPHA_ONEONE | Defines that alpha blending is COLOR=SRC + DEST, ALPHA=DEST_ALPHA |

packages/dev/core/src/States/alphaCullingState.ts

@@ -219,7 +219,6 @@ export class AlphaState {
                 break;
             case Constants.ALPHA_SUBTRACT:
                 this.setAlphaBlendFunctionParameters(0, Constants.GL_ALPHA_FUNCTION_ONE_MINUS_SRC_COLOR, 1, 1, targetIndex);
-                equation = Constants.GL_ALPHA_EQUATION_SUBTRACT;
                 break;
             case Constants.ALPHA_MULTIPLY:
                 this.setAlphaBlendFunctionParameters(Constants.GL_ALPHA_FUNCTION_DST_COLOR, 0, 1, 1, targetIndex);