---
title: "Color Blend State"
date: 2021-01-27T14:11:42-08:00
weight: 1
---

Color blend state is comprised of four fields - a logical operation, whether that logical operation is enabled, some blending constants, and a collection of color *target* blend states. Let's talk about the target states first.

### Color Target Blend State

You might remember our old friend RenderTarget. A color target is just a render target in a color format. Our color target always has color information stored in it - the blend mode tells the renderer how to combine new pixel values with the original values to produce a new color.

`BlendEnable` is a bool. If we turn off blending entirely, the new pixel color will just overwrite any existing values. Simple!

`ColorWriteMask` tells the renderer which color channels it is allowed to write to.

Next we have `AlphaBlendOp` and `ColorBlendOp`, which are `BlendOp` values, and the rest of the fields are `BlendFactor` values. Rather than spend a bunch of time explaining the nuances of various blend modes, I will simply link you to a [very thorough explanation of graphics blending](https://learnopengl.com/Advanced-OpenGL/Blending).

Here is an example blend mode, which does something we call "additive blending". This kind of blending is very useful for lighting and particle effects.

```cs
var myColorTargetBlendState = new ColorTargetBlendState
{
    BlendEnable = true,
    ColorWriteMask = ColorComponentFlags.RGBA,
    AlphaBlendOp = BlendOp.Add,
    ColorBlendOp = BlendOp.Add,
    SourceColorBlendFactor = BlendFactor.SourceAlpha,
    SourceAlphaBlendFactor = BlendFactor.SourceAlpha,
    DestinationColorBlendFactor = BlendFactor.One,
    DestinationAlphaBlendFactor = BlendFactor.One
};
```

Next we have `LogicOp`. This lets you do bitwise combination of the original and new color. You can read about that in more detail [over here](https://www.khronos.org/registry/vulkan/specs/1.2/html/chap28.html#framebuffer-logicop).

`BlendConstants` are used by the blend factors to produce result colors. You can read about that [here](https://www.khronos.org/registry/vulkan/specs/1.2/html/chap28.html#framebuffer-blendconstants).

Let's put it all together:

```cs
var myBlendConstants = new BlendConstants
{
    R = 1f,
    G = 1f,
    B = 1f,
    A = 1f
};

var myColorBlendState = new ColorBlendState
{
    LogicOpEnable = false,
    BlendConstants = myBlendConstants,
    ColorTargetBlendStates = myColorTargetBlendStates
};
```