dolphin/docs/CustomPipelineGraphicsMod.md
2023-08-20 18:53:27 -05:00

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Dolphin Custom Pipeline Specification

Dolphin provides content creators a way to overwrite its internal graphics pipeline data using graphics mods. At the moment, this supports modifying only the pixel shader. This document will describe the specification and give some examples.

Graphics mod metadata format

This feature is powered by graphics mods. This document assumes the user is familiar with them and will only detail the action specific data needed to trigger this capability.

The action type for this feature is custom_pipeline. This action has the following data:

Identifier Required Since
passes Yes v1

passes is an array of pass blobs. Note that at the moment, Dolphin only supports a single pass. Each pass can have the following data:

Identifier Required Since
pixel_material_asset Yes v1

Here pixel_material_asset is the name of a material asset.

A full example is given below:

{
    "assets": [
        {
            "name": "material_replace_normal",
            "data":
            {
                "": "normal.material.json"
            }
        },
        {
            "name": "shader_replace_normal",
            "data":
            {
                "metadata": "replace_normal.shader.json",
                "shader": "replace_normal.glsl"
            }
        },
        {
            "name": "normal_texture",
            "data":
            {
                "": "normal_texture.png"
            }
        }
    ],
    "features": [
        {
            "action": "custom_pipeline",
            "action_data": {
              "passes":  [
                {
                  "pixel_material_asset": "material_replace_normal"
                }
              ]
            },
            "group": "PipelineTarget"
        }
    ],
    "groups": [
       {
            "name": "PipelineTarget",
            "targets": [
                {
                    "texture_filename": "tex1_512x512_m_afdbe7efg332229e_14",
                    "type": "draw_started"
                },
                {
                    "texture_filename": "tex1_512x512_m_afdbe7efg332229e_14",
                    "type": "create_texture"
                }
            ]
       }
    ]
}

The shader format

The shaders are written in GLSL and converted to the target shader that the backend uses internally. The user is expected to provide an entrypoint with the following signature:

vec4 custom_main( in CustomShaderData data )

CustomShaderData encompasses all the data that Dolphin will pass to the user (in addition to the samp variable outlined above which is how textures are accessed). It has the following structure:

Name Type Since Description
position vec3 v1 The position of this pixel in view space
normal vec3 v1 The normal of this pixel in view space
texcoord vec3[] v1 An array of texture coordinates, the amount available is specified by texcoord_count
texcoord_count uint v1 The count of texture coordinates
texmap_to_texcoord_index uint[] v1 An array of texture units to texture coordinate values
lights_chan0_color CustomShaderLightData[] v1 An array of color lights for channel 0, the amount is specified by light_chan0_color_count
lights_chan0_alpha CustomShaderLightData[] v1 An array of alpha lights for channel 0, the amount is specified by light_chan0_alpha_count
lights_chan1_color CustomShaderLightData[] v1 An array of color lights for channel 1, the amount is specified by light_chan1_color_count
lights_chan1_alpha CustomShaderLightData[] v1 An array of alpha lights for channel 1, the amount is specified by light_chan1_alpha_count
ambient_lighting vec4[] v1 An array of ambient lighting values. Count is two, one for each color channel
base_material vec4[] v1 An array of the base material values. Count is two, one for each color channel
tev_stages CustomShaderTevStage[] v1 An array of TEV stages, the amount is specified by tev_stage_count
tev_stage_count uint v1 The count of TEV stages
final_color vec4 v1 The final color generated by Dolphin after all TEV stages are executed

CustomShaderLightData is used to denote lighting data the game is applying when rendering the specific draw call. It has the following structure:

Name Type Since Description
position vec3 v1 The position of the light in view space
direction vec3 v1 The direction in view space the light is pointing (only applicable for point and spot lights)
color vec3 v1 The color of the light
attenuation_type uint v1 The attentuation type of the light. See details below
cosatt vec4 v1 The cos attenuation values used
distatt vec4 v1 The distance attenuation values used

The attenuation_type is defined as a uint but is effecitvely an enumeration. It has the following values:

Name Since Description
CUSTOM_SHADER_LIGHTING_ATTENUATION_TYPE_POINT v1 This value denotes the lighting attentuation is for a point light
CUSTOM_SHADER_LIGHTING_ATTENUATION_TYPE_DIR v1 This value denotes the lighting attentuation is for a directional light
CUSTOM_SHADER_LIGHTING_ATTENUATION_TYPE_SPOT v1 This value denotes the lighting attentuation is for a directional light

CustomShaderTevStage is used to denote the various TEV operations. Each operation describes a graphical operation that the game is applying when rendering the specific draw call. It has the following structure:

Name Type Since Description
input_color CustomShaderTevStageInputColor[] v1 The four color inputs that are used to produce the final output of this stage
input_alpha CustomShaderTevStageInputAlpha[] v1 The four alpha inputs that are used to produce the final output of this stage
texmap uint v1 The texture unit for this stage
output_color vec4 v1 The final output color this stage produces

CustomShaderTevStageInputColor is a single input TEV operation for a color value. It has the following structure:

Name Type Since Description
input_type uint v1 The input type of the input. See details below
value vec3 v1 The value of input

The input_type is defined as a uint but is effectively an enumeration. it has the following values:

Name Since Description
CUSTOM_SHADER_TEV_STAGE_INPUT_TYPE_PREV v1 The value is provided by the last stage
CUSTOM_SHADER_TEV_STAGE_INPUT_TYPE_COLOR v1 The value is provided by the color data
CUSTOM_SHADER_TEV_STAGE_INPUT_TYPE_TEX v1 The value is provided by a texture
CUSTOM_SHADER_TEV_STAGE_INPUT_TYPE_RAS v1
CUSTOM_SHADER_TEV_STAGE_INPUT_TYPE_KONST v1 The value is a constant value defined by the software
CUSTOM_SHADER_TEV_STAGE_INPUT_TYPE_NUMERIC v1 The value is a constant numeric value like vec3(0, 0, 0) or vec3(1, 1, 1)

CustomShaderTevStageInputAlpha is a single input TEV operation for an alpha value. It has the following structure:

Name Type Since Description
input_type uint v1 The input type of the input. See input_type for color input stages
value uint v1 The value of input

Examples

Below are a handful of examples.

Single color

The following shader displays the color red on the screen:

vec4 custom_main( in CustomShaderData data )
{
	return vec4(1.0, 0.0, 0.0, 1.0);
}

Normal

The following shader displays the normal on the screen:

vec4 custom_main( in CustomShaderData data )
{
	return vec4(data.normal * 0.5 + 0.5, 1);
}

Reading a texture

The following shader displays the contents of the texture denoted in the shader asset as MY_TEX:

vec4 custom_main( in CustomShaderData data )
{
	return texture(samp[MY_TEX_UNIT], MY_TEX_COORD);
}

Capturing the first texture the game renders with

The following shader would display the contents of the first texture the game uses, ignoring any other operations. If no stages are available or none exist with a texture it would use the final color of all the staging operations:

vec4 custom_main( in CustomShaderData data )
{
	vec4 final_color = data.final_color;
	uint texture_set = 0;
	for (uint i = 0; i < data.tev_stage_count; i++)
	{
		// There are 4 color inputs
		for (uint j = 0; j < 4; j++)
		{
			if (data.tev_stages[i].input_color[j].input_type == CUSTOM_SHADER_TEV_STAGE_INPUT_TYPE_TEX && texture_set == 0)
			{
				final_color = vec4(data.tev_stages[i].input_color[j].value, 1.0);
				texture_set = 1;
			}
		}
	}

	return final_color;
}

Applying lighting with a point type attenuation

The following shader would apply the lighting for any point lights used during the draw for channel 0's color lights, using blue as a base color:

vec4 custom_main( in CustomShaderData data )
{
	float total_diffuse = 0;
	for (int i = 0; i < data.light_chan0_color_count; i++)
	{
		if (data.lights_chan0_color[i].attenuation_type == CUSTOM_SHADER_LIGHTING_ATTENUATION_TYPE_POINT)
		{
			vec3 light_dir = normalize(data.lights_chan0_color[i].position - data.position.xyz);
			float attn = (dot(normal, light_dir) >= 0.0) ? max(0.0, dot(normal, data.lights_chan0_color[i].direction.xyz)) : 0.0;
			vec3 cosAttn = data.lights_chan0_color[i].cosatt.xyz;
			vec3 distAttn = data.lights_chan0_color[i].distatt.xyz;
			attn = max(0.0, dot(cosAttn, vec3(1.0, attn, attn*attn))) / dot(distAttn, vec3(1.0, attn, attn * attn));
			total_diffuse += attn * max(0.0, dot(normal, light_dir));
		}
	}
	return vec4(total_diffuse * vec3(0, 0, 1), 1);
}