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Pass

Pass "PassName" {
  Tag {PipelineStage = "ShadowCaster"}
 
  ...
  // Glbals
  ...
 
  // Render pipeline and render state settings
 
  // Specify the entry function of shader
  VertexShader = vert;
 
  // Specify render queue
  RenderQueueType = Transparent;
}

Pass is the basic element of a Shader object. A simple shader object may contain only one Pass, but more complex shaders can contain multiple Passes. It defines the operations performed at specific stages of the rendering pipeline, such as the shader programs running on the GPU, rendering states, and settings related to the rendering pipeline.

Rendering State

It can be specified in the following two ways:

  1. Explicit assignment
BlendState = blendState;
  1. Declaration in the global variable domain of Pass
BlendState {
  Rendering state property = Property value;
}

Specifying uniform Variables

Directly declare them as global variables

mediump vec4 u_color;
float material_AlphaCutoff;
mat4 renderer_ModelMat;
vec3 u_lightDir;

Declaring varying Variables

Specify by defining the output structure of the vertex shader and the input structure of the fragment shader

struct v2f {
  vec3 color;
};
 
v2f vert(a2v o) {
  ...
}
 
void frag(v2f i) {
  ...
}

Specifying Vertex and Fragment Shaders

Explicitly specify the shader entry functions using VertexShader and FragmentShader

VertexShader = vert;
FragmentShader = frag;

Setting the Render Queue

Specify using the RenderQueueType directive, which is equivalent to the engine API.

RenderQueueType = Transparent;

In addition to setting the render state and render queue in ShaderLab, developers can also configure these settings through the material API, such as:

// Render queue setting
material.renderQueueType = RenderQueueType.Opaque;
 
// Render state setting const renderState = material.renderState.depthState; depthState.writeEnabled = false;

When render states and render queues are declared in ShaderLab, the corresponding settings in the material will be ignored."


## MRT(Multiple Render Targets)

ShaderLab is compatible with both GLSL 100 and GLSL 300 syntax, allowing you to specify MRT using either syntax.

1. Specify MRT using `gl_FragData[i]`.

```glsl
void main(v2f input) {
  gl_FragData[0] = vec4(1.,0.,0.,1.);     // render target 0
  gl_FragData[1] = vec4(1.,0.,0.,1.);     // render target 1
}
  1. Specify by returning a struct from the entry function
struct mrt {
  layout(location = 0) vec4 fragColor0;   // render target 0
  layout(location = 1) vec4 fragColor1;   // render target 1
}
 
mrt main(v2f input) {
  mrt output;
  output.fragColor0 = vec4(1.,0.,0.,1.);
  output.fragColor1 = vec4(1.,0.,0.,1.);
  return output;
}

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