Issue with using HLMS low-level material script on Metal

[taesoobear]

I am implementing Gaussian splatting rendering using ogre-next v3. I’m not sure how to implement this using Unlit, so I’m using HLMS low-level instead. Currently, the HLMS low-level material script works in GLSL and HLSL, but it does not work on Metal. How can I fix this?
Problematic part 1: It seems that param_named_auto is not working.

vertex_program gsplatting_vp_glsl glsl glsles glslang
{
	source gsplat_quad_vp.glsl
    enable_include_header true
}
vertex_program gsplatting_vp_hlsl hlsl
{
    source gsplat_quad_vp.hlsl
    entry_point main
    target vs_5_0 vs_4_0
}
vertex_program gsplatting_vp_metal metal
{
    source gsplat_quad_vp.metal
    entry_point main_metal
}
vertex_program gsplatting_vp unified
{
	delegate gsplatting_vp_glsl
	delegate gsplatting_vp_hlsl
	delegate gsplatting_vp_metal

	default_params
	{
		param_named_auto projmatrix worldviewproj_matrix
		param_named_auto viewmatrix worldview_matrix
		param_named_auto vpsize viewport_size
		param_named_auto fovy fov
	}
}

fragment_program gsplatting_fp_glsl glsl glsles glslang
{
	source gsplat_quad_fp.glsl
}

fragment_program gsplatting_fp_hlsl hlsl
{
    source gsplat_quad_fp.hlsl
    entry_point main
    target ps_5_0
}
fragment_program gsplatting_fp_metal metal
{
    source gsplat_quad_fp.metal
    entry_point main_metal
}
fragment_program gsplatting_fp unified
{
    delegate gsplatting_fp_glsl
    delegate gsplatting_fp_hlsl
    delegate gsplatting_fp_metal
}
material pointcloud_quad
{
	receive_shadows off   
    technique 
    {
        pass
        {
            scene_blend alpha_blend
            depth_write off

            vertex_program_ref gsplatting_vp
            {
            }

            fragment_program_ref gsplatting_fp
            {
            }
        }
    }
}

struct Uniforms
{
    float4x4 projmatrix;
    float4x4 viewmatrix;
    float    fovy;
    float4   vpsize;
};

vertex VS_OUTPUT main_metal(VS_INPUT in [[stage_in]],
                         constant Uniforms& u [[buffer(0)]])

I also tried getting the uniform inputs separately. For example, const float4x4& projmatrix [[buffer(0)]], viewmarix [[buffer(1)]], and so on.

Problematic part 2: I’m not sure how to pass the input data to the vertex shader.

struct VS_INPUT
{    
float3 position [[attribute(0)]];    
float4 colour   [[attribute(1)]];    
float3 uv0      [[attribute(2)]];    
float3 uv1      [[attribute(3)]];    
float2 uv2      [[attribute(4)]];
};

Error message:

07:07:27: OGRE EXCEPTION(3:RenderingAPIException): Failed to create pipeline state for rendering, error: Vertex attribute colour(1) is missing from the vertex descriptor in MetalRenderSystem::_hlmsPipelineStateObjectCreated at /Users/taesookwon/ogre-next32/RenderSystems/Metal/src/OgreMetalRenderSystem.mm (line 1752)

[taesoobear]

Okay, this pattern seems to work. I will look further into it.

 uint                         vertexID [[vertex_id]],         
    constant VS_INPUT*       vb       [[buffer(0)]],     
                         constant Uniforms& u [[buffer(PARAMETER_SLOT)]])
{
VS_INPUT in=vb[vertexID];
...

[taesoobear]

No, the above pattern doesn't work, and this pattern works.

struct VS_INPUT
{
    float3 position [[attribute(0)]];
    float4 colour   [[attribute(5)]]; // VES_DIFFUSE
    float3 uv0      [[attribute(7)]];
    float3 uv1      [[attribute(8)]];
    float2 uv2      [[attribute(9)]];
};
vertex VS_OUTPUT main_metal(
	VS_INPUT in [[stage_in]],
		constant Uniforms& u [[buffer(PARAMETER_SLOT)]])
{

[darksylinc]

Hi, use [[attribute(VES_POSITION)]] and the corresponding VES_* (including VES_TEXTURE_COORDINATES0 ... VES_TEXTURE_COORDINATES7).

See how the other vertex shaders for Metal in the Samples are doing it.