public void setBlendMode(BlendMode blendMode) {
        applyBlendMode = true;
        this.blendMode = blendMode;
        cachedHashCode = -1;
    }
Set the blending mode.

<p>When blending is enabled, (<code>blendMode</code> is not {@link BlendMode#Off})
the input pixel will be blended with the pixel
already in the color buffer. The blending operation is determined
by the {@link BlendMode}. For example, the {@link BlendMode#Additive}
will add the input pixel's color to the color already in the color buffer:
<br>
<code>Result = Source Color + Destination Color</code>

@param blendMode The blend mode to use. Set to {@link BlendMode#Off}
to disable blending.
jme3-core/src/main/java/com/jme3/material/RenderState.java