ogre-next 学习笔记 - Day 7

ogre-next 学习笔记 - Day 7

通过之前的分析，知晓 hlms 的重要性。对hlms做一个详细的分析

hlms文件结构以及对象

从图中看出，hlms的文件不多，对象也不多，关系简单。

类图

能看懂就行，不求格式

对象大概能分为几类

• Hlms
• HlmsProperty
• HlmsDatablock
• StaticBlock
• HlmsJson
• 其他

每一种 hlms都有一个对应的property，这些property由一些const idString 标识它支持的属性。
例如

    struct _OgreHlmsUnlitMobileExport UnlitMobileProp
    {
        static const IdString TexMatrixCount;
        static const IdString TexMatrixCount0;
        static const IdString TexMatrixCount1;
        static const IdString TexMatrixCount2;
        static const IdString TexMatrixCount3;
        static const IdString TexMatrixCount4;
        static const IdString TexMatrixCount5;
        static const IdString TexMatrixCount6;
        static const IdString TexMatrixCount7;
		// ...
   }
    const IdString UnlitMobileProp::TexMatrixCount      = IdString( "hlms_texture_matrix_count" );
    const IdString UnlitMobileProp::TexMatrixCount0     = IdString( "hlms_texture_matrix_count0" );
    const IdString UnlitMobileProp::TexMatrixCount1     = IdString( "hlms_texture_matrix_count1" );
    const IdString UnlitMobileProp::TexMatrixCount2     = IdString( "hlms_texture_matrix_count2" );
    const IdString UnlitMobileProp::TexMatrixCount3     = IdString( "hlms_texture_matrix_count3" );
    const IdString UnlitMobileProp::TexMatrixCount4     = IdString( "hlms_texture_matrix_count4" );
    const IdString UnlitMobileProp::TexMatrixCount5     = IdString( "hlms_texture_matrix_count5" );
    const IdString UnlitMobileProp::TexMatrixCount6     = IdString( "hlms_texture_matrix_count6" );
    const IdString UnlitMobileProp::TexMatrixCount7     = IdString( "hlms_texture_matrix_count7" );

每个hlms 都有一个 datablock
例如

class HlmsUnlitMobileDatablock : public HlmsDatablock
{
	 /** Valid parameters in params:
        @param params
            * diffuse [r g b [a]]
                If absent, the values of mR, mG, mB & mA will be ignored by the pixel shader.
                When present, the rgba values can be specified.
                Default: Absent
                Default (when present): diffuse 1 1 1 1

            * diffuse_map [texture name] [#uv]
                Name of the diffuse texture for the base image (optional, otherwise a dummy is set)
                The #uv parameter is optional, and specifies the texcoord set that will
                be used. Valid range is [0; 8)
                If the Renderable doesn't have enough UV texcoords, HLMS will throw an exception.

                Note: The UV set is evaluated when creating the Renderable cache.

            * diffuse_map1 [texture name] [blendmode] [#uv]
                Name of the diffuse texture that will be layered on top of the base image.
                The #uv parameter is optional. Valid range is [0; 8)
                The blendmode parameter is optional. Valid values are:
                    NormalNonPremul, NormalPremul, Add, Subtract, Multiply,
                    Multiply2x, Screen, Overlay, Lighten, Darken, GrainExtract,
                    GrainMerge, Difference
                which are very similar to Photoshop/GIMP's blend modes.
                See Samples/Media/Hlms/GuiMobile/GLSL/BlendModes_piece_ps.glsl for the exact math.
                Default blendmode:      NormalPremul
                Default uv:             0
                Example: diffuse_map1 myTexture.png Add 3

             * diffuse_map2 through diffuse_map16
                Same as diffuse_map1 but for subsequent layers to be applied on top of the previous
                images. You can't leave gaps (i.e. specify diffuse_map0 & diffuse_map2 but not
                diffuse_map1).
                Note that not all mobile HW supports 16 textures at the same time, thus we will
                just cut/ignore the extra textures that won't fit (we log a warning though).

             * animate <#uv> [<#uv> <#uv> ... <#uv>]
                Enables texture animation through a 4x4 matrix for the specified UV sets.
                Default: All UV set animation/manipulation disabled.
                Example: animate 0 1 2 3 4 5 6 7

             * alpha_test [compare_func] [threshold]
                When present, mAlphaTestThreshold is used.
                compare_func is optional. Valid values are:
                    less, less_equal, equal, greater, greater_equal, not_equal
                Threshold is optional, and a value in the range (0; 1)
                Default: alpha_test less 0.5
                Example: alpha_test equal 0.1
        */
}

这里通过注释的方式，把每个支持的数据都标出来了。通过之前的学习知道，这些数据可以来自script，也可以通过代码设置。

datablock里的数据与property里的是一一对应的，renderable持有了一个datablock，最终会把 datablock里的数据设置到property里。

void HlmsPbs::calculateHashForPreCreate( Renderable *renderable, PiecesMap *inOutPieces )
{
	assert( dynamic_cast<HlmsPbsDatablock*>( renderable->getDatablock() ) );
        HlmsPbsDatablock *datablock = static_cast<HlmsPbsDatablock*>(
                                                        renderable->getDatablock() );

        const bool metallicWorkflow = datablock->getWorkflow() == HlmsPbsDatablock::MetallicWorkflow;
        const bool fresnelWorkflow = datablock->getWorkflow() ==
                                                        HlmsPbsDatablock::SpecularAsFresnelWorkflow;

        setProperty( PbsProperty::FresnelScalar, datablock->hasSeparateFresnel() || metallicWorkflow );
        setProperty( PbsProperty::FresnelWorkflow, fresnelWorkflow );
        setProperty( PbsProperty::MetallicWorkflow, metallicWorkflow );
// ...

}

已知的是，创建的时候是通过item->setDatablock(…)

    void Item::setDatablock( HlmsDatablock *datablock )
    {
        SubItemVec::iterator itor = mSubItems.begin();
        SubItemVec::iterator end  = mSubItems.end();

        while( itor != end )
        {
            itor->setDatablock( datablock );
            ++itor;
        }
    }

内部会调用 subItem->setDatablock(…)

void Renderable::setDatablock( HlmsDatablock *datablock )
{
// ...
}

class _OgreExport SubItem : public RenderableAnimated

class _OgreExport RenderableAnimated : public Renderable

SubItem 是 Renderable。

从material 到 hlms property，hlms 算走通了一半。设置完属性后，就应该设置往shader送数据了。
还有 hlms的几个cache没有涉及到

to be continue…