TextureMergerRenderer

The TextureMergerRenderer class composes multiple input textures into a single merged texture output. It creates its own render buffer and uses the TextureMergerShader to combine textures per-channel.

Constructor

constructor(renderer: Renderer)

Creates the internal TextureMergerShader (singleton via GetUnique()), a merged output texture, and attaches it to a render buffer.

Properties

renderer

The owning Renderer instance.

dirty : boolean

Indicates whether the merged texture needs regeneration. Set to true automatically whenever a channel texture is modified via setTexture().

mergedTexture : Texture

The output texture containing the merged result. Uses COLOR_ATTACHMENT_0 with UNSIGNED_BYTE format and REPEAT wrap mode.

isComplete : boolean

Forwarded from the shader’s isComplete flag. Indicates if all required textures are loaded and valid.

Methods

setTexture(tex: Texture, channel: TextureChannel, dstChannel?: TextureChannel)

Sets the source texture for a specific input channel and specifies which destination channel the data should map to.

// Set R channel from a grayscale texture, outputting to channel A
renderer.setTexture(grayTex, TextureChannel.R, TextureChannel.A);

// Set G channel from another texture, outputting to channel R
renderer.setTexture(colorTex, TextureChannel.G, TextureChannel.R);

// Set all four channels to create ARGB output
merger.setTexture(rTex, TextureChannel.R);              // defaults to dst R
merger.setTexture(gTex, TextureChannel.G);              // defaults to dst G
merger.setTexture(BTex, TextureChannel.B);              // defaults to dst B
merger.setTexture(aTex, TextureChannel.A, TextureChannel.A);  // explicit alpha mapping

If tex is null, throws an error. Automatically marks the merger as dirty.

update()

Regenerates the merged texture if dirty. Internally calls renderer.presentTexture() twice (a workaround as noted in the source code):

merger.update();  // Only renders if dirty is true

The implementation:

1. Calls update() on the internal render buffer with a draw callback
2. Calls presentTexture twice — once with clears and once without (debug note about why this is needed)
3. Resets dirty flag on completion

Internal RenderBuffer Usage

A render buffer is automatically created and attached to mergedTexture. The merger reuses this buffer for each update cycle, which is why two passes are needed.

Typical Usage Pattern

const merger = new TextureMergerRenderer(renderer);

merger.setTexture(alphaTexture, TextureChannel.R, TextureChannel.A);
merger.update();  // Generates merged result

// Access the output
const resultTex = merger.mergedTexture;