虚幻4 添加变量控制UI的渲染，详细教程。
首先更改UI的shader。
结构体：
Engine_Updating\Engine\Shaders\SlateShaderCommon.usf
struct VertexToPixelInterpolants
{
float4 Position : SV_POSITION;
float4 Color : COLOR0;
float4 ClipOriginAndPos : TEXCOORD0;
float4 ClipExtents : TEXCOORD1;
float2 MaterialTexCoords : TEXCOORD2;
float4 TextureCoordinates[NUM_SLATE_TEXCOORDS] : TEXCOORD3;
float DisableValue:TEXCOORD4;
};VertexShader:
Engine_Updating\Engine\Shaders\SlateVertexShader.usf
VertexToPixelInterpolants Main(
in float4 InTextureCoordinates : ATTRIBUTE0,
in float2 InMaterialTextureCoordinates : ATTRIBUTE1,
in float2 InPosition : ATTRIBUTE2,
in float2 InClipOrigin : ATTRIBUTE3,
in float4 InClipExtents : ATTRIBUTE4,
in float4 InColor : ATTRIBUTE5,
in float InDisableValue : ATTRIBUTE6
#if USE_SLATE_INSTANCING
, in float4 InstanceParam : ATTRIBUTE7
#endif
)
{
VertexToPixelInterpolants VOut = (VertexToPixelInterpolants)0;
float4 WorldPosition = float4(InPosition.xy,0,1);
#if (!(ES2_PROFILE || ES3_1_PROFILE)) || USE_MATERIALS
InColor.rgb = sRGBToLinear(InColor.rgb);
#endif
float4 FinalVertexColor = InColor FCOLOR_COMPONENT_SWIZZLE;
VOut.MaterialTexCoords = InMaterialTextureCoordinates;
VOut.ClipOriginAndPos = float4(InClipOrigin, InPosition.xy);
VOut.ClipExtents = InClipExtents;
VOut.Color = FinalVertexColor;
VOut.TextureCoordinates[0] = InTextureCoordinates;
VOut.DisableValue = InDisableValue;
PixelShader:
Engine_Updating\Engine\Shaders\SlateElementPixelShader.usf
#if DRAW_DISABLED_EFFECT
//desaturate
float3 LumCoeffs = float3( 0.3, 0.59, .11 );
float Lum = dot( LumCoeffs, OutColor.rgb );
OutColor.rgb = lerp( OutColor.rgb, float3(Lum,Lum,Lum), VIn.DisableValue );
//float3 Grayish = {.1, .1, .1};
//OutColor.rgb = lerp( OutColor.rgb, 3, clamp( distance( OutColor.rgb, Grayish ), 0, .8) );
#endif然后更改代码。
这是给UI Vetex Shader的参数，因为我们加了一个参数，所以要在这里添加一个对应的参数。
SlateCore/Public/Rendering/RenderingCommon.h
struct SLATECORE_API FSlateVertex
{
/** Texture coordinates. The first 2 are in xy and the 2nd are in zw */
float TexCoords[4];
/** Texture coordinates used as pass through to materials for custom texturing. */
float MaterialTexCoords[2];
/** Position of the vertex in window space */
float Position[2];
/** clip center/extents in render window space (window space with render transforms applied) */
FSlateRotatedClipRectType ClipRect;
/** Vertex color */
FColor Color;
/** **/
float DisableValue;
FSlateVertex();
FSlateVertex( const FSlateRenderTransform& RenderTransform, const FVector2D& InLocalPosition, const FVector2D& InTexCoord, const FVector2D& InTexCoord2, const FColor& InColor, const FSlateRotatedClipRectType& InClipRect , float InDisableValue);
FSlateVertex(const FSlateRenderTransform& RenderTransform, const FVector2D& InLocalPosition, const FVector2D& InTexCoord, const FColor& InColor, const FSlateRotatedClipRectType& InClipRect, float InDisableValue);
FSlateVertex(const FSlateRenderTransform& RenderTransform, const FVector2D& InLocalPosition, const FVector4& InTexCoords, const FVector2D& InMaterialTexCoords, const FColor& InColor, const FSlateRotatedClipRectType& InClipRect, float InDisableValue);
};对应的构造函数我就不写了，就是给DisableValue赋值。
然后在FSlateDrawElement里面添加变量：
SlateCore/Public/Rendering/DrawElements.h
FORCEINLINE const TOptional& GetScissorRect() const { return ScissorRect; }
/**/
FORCEINLINE float GetDisableValue() const { return DisableValue; }
private:
void Init(uint32 InLayer, const FPaintGeometry& PaintGeometry, const FSlateRect& InClippingRect, ESlateDrawEffect::Type InDrawEffects);
static FVector2D GetRotationPoint( const FPaintGeometry& PaintGeometry, const TOptional& UserRotationPoint, ERotationSpace RotationSpace );
private:
FSlateDataPayload DataPayload;
FSlateRenderTransform RenderTransform;
FSlateRect ClippingRect;
FVector2D Position;
FVector2D LocalSize;
float Scale;
uint32 Layer;
uint32 DrawEffects;
EElementType ElementType;
TOptional ScissorRect;
/**/
float DisableValue;
};
这几个函数添加参数：
SLATECORE_API static void MakeBox(
FSlateWindowElementList& ElementList,
uint32 InLayer,
const FPaintGeometry& PaintGeometry,
const FSlateBrush* InBrush,
const FSlateRect& InClippingRect,
ESlateDrawEffect::Type InDrawEffects = ESlateDrawEffect::None,
const FLinearColor& InTint = FLinearColor::White ,
float InDisableValue = 0.8);
SLATECORE_API static void MakeBox(
FSlateWindowElementList& ElementList,
uint32 InLayer,
const FPaintGeometry& PaintGeometry,
const FSlateBrush* InBrush,
const FSlateResourceHandle& InRenderingHandle,
const FSlateRect& InClippingRect,
ESlateDrawEffect::Type InDrawEffects = ESlateDrawEffect::None,
const FLinearColor& InTint = FLinearColor::White,
float InDisableValue = 0.8);
然后MakeBox函数体里面赋值就不写了。
剩下的就是全局搜索FSlateVertex，把所有的构造FSlateVertex的地方，把FSlateDrawElement里面变量传进去。（不想使用默认的参数值）
改变CPP里面定义的传入参数。
SlateRHIRenderer/Private/SlateShaders.cpp
/************************************************************************/
/* FSlateVertexDeclaration */
/************************************************************************/
void FSlateVertexDeclaration::InitRHI()
{
FVertexDeclarationElementList Elements;
uint32 Stride = sizeof(FSlateVertex);
Elements.Add(FVertexElement(0, STRUCT_OFFSET(FSlateVertex, TexCoords), VET_Float4, 0, Stride));
Elements.Add(FVertexElement(0, STRUCT_OFFSET(FSlateVertex, MaterialTexCoords), VET_Float2, 1, Stride));
Elements.Add(FVertexElement(0, STRUCT_OFFSET(FSlateVertex, Position), VET_Float2, 2, Stride));
Elements.Add(FVertexElement(0, STRUCT_OFFSET(FSlateVertex, ClipRect) + STRUCT_OFFSET(FSlateRotatedClipRectType, TopLeft), VET_Float2, 3, Stride));
Elements.Add(FVertexElement(0, STRUCT_OFFSET(FSlateVertex, ClipRect) + STRUCT_OFFSET(FSlateRotatedClipRectType, ExtentX), VET_Float4, 4, Stride));
Elements.Add(FVertexElement(0, STRUCT_OFFSET(FSlateVertex, Color), VET_Color, 5, Stride));
Elements.Add(FVertexElement(0, STRUCT_OFFSET(FSlateVertex, DisableValue), VET_Float1, 6, Stride));
VertexDeclarationRHI = RHICreateVertexDeclaration(Elements);
}
void FSlateVertexDeclaration::ReleaseRHI()
{
VertexDeclarationRHI.SafeRelease();
}
/************************************************************************/
/* FSlateInstancedVertexDeclaration */
/************************************************************************/
void FSlateInstancedVertexDeclaration::InitRHI()
{
FVertexDeclarationElementList Elements;
uint32 Stride = sizeof(FSlateVertex);
Elements.Add(FVertexElement(0, STRUCT_OFFSET(FSlateVertex, TexCoords), VET_Float4, 0, Stride));
Elements.Add(FVertexElement(0, STRUCT_OFFSET(FSlateVertex, MaterialTexCoords), VET_Float2, 1, Stride));
Elements.Add(FVertexElement(0, STRUCT_OFFSET(FSlateVertex, Position), VET_Float2, 2, Stride));
Elements.Add(FVertexElement(0, STRUCT_OFFSET(FSlateVertex, ClipRect) + STRUCT_OFFSET(FSlateRotatedClipRectType, TopLeft), VET_Float2, 3, Stride));
Elements.Add(FVertexElement(0, STRUCT_OFFSET(FSlateVertex, ClipRect) + STRUCT_OFFSET(FSlateRotatedClipRectType, ExtentX), VET_Float4, 4, Stride));
Elements.Add(FVertexElement(0, STRUCT_OFFSET(FSlateVertex, Color), VET_Color, 5, Stride));
/**/
Elements.Add(FVertexElement(0, STRUCT_OFFSET(FSlateVertex, DisableValue), VET_Float1, 6, Stride));
Elements.Add(FVertexElement(1, 0, VET_Float4, 7, sizeof(FVector4), true));
VertexDeclarationRHI = RHICreateVertexDeclaration(Elements);
}
最后一步
Slate/Private/Widgets/Images/SImage.cpp
int32 SImage::OnPaint( const FPaintArgs& Args, const FGeometry& AllottedGeometry, const FSlateRect& MyClippingRect, FSlateWindowElementList& OutDrawElements, int32 LayerId, const FWidgetStyle& InWidgetStyle, bool bParentEnabled ) const
{
const FSlateBrush* ImageBrush = Image.Get();
if ((ImageBrush != nullptr) && (ImageBrush->DrawAs != ESlateBrushDrawType::NoDrawType))
{
const bool bIsEnabled = ShouldBeEnabled(bParentEnabled);
const uint32 DrawEffects = bIsEnabled ? ESlateDrawEffect::None : ESlateDrawEffect::DisabledEffect;
const FLinearColor FinalColorAndOpacity( InWidgetStyle.GetColorAndOpacityTint() * ColorAndOpacity.Get().GetColor(InWidgetStyle) * ImageBrush->GetTint( InWidgetStyle ) );
FSlateDrawElement::MakeBox(OutDrawElements, LayerId, AllottedGeometry.ToPaintGeometry(), ImageBrush, MyClippingRect, DrawEffects, FinalColorAndOpacity ,0.3);
}
return LayerId;
}可以看到我传入的0.3，默认是0.8，所以编译以后，所有图片的DISABLE状态，灰色不会有这么明显了，但是button还是0.8的默认灰色。
应该是没有漏下东西，如果看过前面的文章的话，就可以通过UMG吧这个值暴露给编辑器，就可以通过改变一个字段改变一个特定UI的DISABLE的灰色的程度。
完成