Question

While trying to figure out terminology for rendering, I came down to this problem as I could not see the difference.

What is the difference between “Alpha Enabled” and “Blending Enabled”?

Answer 1

It would be nice to get a bit more context such as OpenGL programming – terminology can be surprisingly inconsistent across different standards, companies, software, and disciplines.

This article approaches it from an OpenGL perspective, where you can consider alpha to be transparency. Alpha generally refers the transparency of a color (ARGB) or texture (the alpha channel). This is a bit more nuanced when it comes to OpenGL though.

15.010 What is the difference between transparent, translucent, and blended primitives?

A transparent physical material shows objects behind it as unobscured and doesn’t reflect light off its surface. Clear glass is a nearly transparent material. Although glass allows most light to pass through unobscured, in reality it also reflects some light. A perfectly transparent material is completely invisible.

A translucent physical material shows objects behind it, but those objects are obscured by the translucent material. In addition, a translucent material reflects some of the light that hits it, making the material visible. Physical examples of translucent materials include sheer cloth, thin plastic, and smoked glass.

Transparent and translucent are often used synonymously. Materials that are neither transparent nor translucent are opaque.

Blending is OpenGL’s mechanism for combining color already in the framebuffer with the color of the incoming primitive. The result of this combination is then stored back in the framebuffer. Blending is frequently used to simulate translucent physical materials. One example is rendering the smoked glass windshield of a car. The driver and interior are still visible, but they are obscured by the dark color of the smoked glass.