HLSL“优化”使用的变量

如何解决HLSL“优化”使用的变量

这是我的 2d 多边形着色器。出于某种原因，即使顶点着色器穿过所有墙壁，编译器仍将其视为未使用的变量并将其优化掉，这意味着当我尝试从 monogame 实际设置参数时，该参数为空没有设置。我不明白为什么着色器认为 'walls' 变量显然没有被使用。

#if OPENGL
    #define SV_POSITION POSITION
    #define VS_SHADERMODEL vs_3_0
    #define PS_SHADERMODEL ps_3_0
#else
    #define VS_SHADERMODEL vs_4_0_level_9_1
    #define PS_SHADERMODEL ps_4_0_level_9_1
#endif

matrix WorldViewProjection;
float4 walls[6];
float2 lightPos = float2(0,0);
float4 lightColor = float4(0,1.0);

struct VertexShaderInput
{
    float4 Position : POSITION0;
    float4 Color : COLOR0;
};

struct VertexShaderOutput
{
    float4 Position : SV_Position;
    float4 Color : COLOR0;
    float2 ScreenPos : TEXCOORD0;
};


int orientation(float2 p,float2 q,float2 r)
{
    int val = (q.y - p.y) * (r.x - q.x) -
        (q.x - p.x) * (r.y - q.y);
    if (val == 0)
        return 0;
    if (val > 0)
        return 1;
    return 2;
}

bool onSegment(float2 p,float2 r)
{
    if (q.x <= max(p.x,r.x) && q.x >= min(p.x,r.x) &&
        q.y <= max(p.y,r.y) && q.y >= min(p.y,r.y))
        return true;
    return false;
}

bool intersect(float2 p1,float2 q1,float2 p2,float2 q2)
{
    int o1 = orientation(p1,q1,p2);
    int o2 = orientation(p1,q2);
    int o3 = orientation(p2,q2,p1);
    int o4 = orientation(p2,q1);

    if (o1 != o2 && o3 != o4)
        return true;

    if (o1 == 0 && onSegment(p1,p2,q1))
        return true;
    if (o2 == 0 && onSegment(p1,q1))
        return true;
    if (o3 == 0 && onSegment(p2,p1,q2))
        return true;
    if (o4 == 0 && onSegment(p2,q2))
        return true;

    return false;
}

float map(float value,float min1,float max1,float min2,float max2)
{
    return min2 + (value - min1) * (max2 - min2) / (max1 - min1);
}


VertexShaderOutput MainVS(in VertexShaderInput input)
{
    VertexShaderOutput output = (VertexShaderOutput)0;
    
    float2 screenPos = input.Position.xy;
    output.ScreenPos = screenPos;
    output.Position = mul(input.Position,WorldViewProjection);
    
    bool collided = true;
    
    //Run through all the wall segments and make sure light actually hits this vertex
    for (int i = 0; i < 6; i++)
    {
        float2 p = float2(walls[i].x,walls[i].y),q = float2(walls[i].z,walls[i].w);
        
        if (intersect(lightPos,screenPos,p,q))
        {
            //The light hits a wall before hitting this vertex
            collided = false;
        }
    }
    
    float4 color = input.Color;
    
    if (!collided)
    {
        color = float4(0,0);
    }
    else
    {
        color *= lightColor;
        color.a = map(distance(screenPos,lightPos),150,1.0f,0);
    }
    output.Color = color;
    
    return output;
}


float4 MainPS(VertexShaderOutput input) : COLOR
{
    return input.Color;
}

technique BasicColorDrawing
{
    pass P0
    {
        VertexShader = compile VS_SHADERMODEL MainVS();
        PixelShader = compile PS_SHADERMODEL MainPS();
    }
};

解决方法

通过在循环前添加 [unroll] 允许设置 wall 变量并随后在顶点着色器中解析数组，能够摆脱编译器优化。