在黑暗的环境光上应用聚光灯 - HLSL - Monogame

我为我的 Monogame 项目编写了一个 HLSL 着色器，它使用环境照明来创建日/夜循环。

#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

sampler s0;

struct VertexShaderOutput
{
    float4 Position : SV_POSITION;
    float4 Color : COLOR0;
    float2 TextureCoordinates : TEXCOORD0;
};


float ambient = 1.0f;
float percentThroughDay = 0.0f;

float4 MainPS(VertexShaderOutput input) : COLOR
{
    float4 pixelColor = tex2D(s0, input.TextureCoordinates);
    float4 outputColor = pixelColor;

    // lighting intensity is gradient of pixel position
    float Intensity = 1 + (1  - input.TextureCoordinates.y) * 1.3;
    outputColor.r = outputColor.r / ambient * Intensity;
    outputColor.g = outputColor.g / ambient * Intensity;
    outputColor.b = outputColor.b / ambient * Intensity;

    // sun set/rise blending 
    float exposeRed = (1 + (.39 - input.TextureCoordinates.y) * 8); // overexpose red
    float exposeGreen = (1 + (.39 - input.TextureCoordinates.y) * 2); // some extra green for the blue pixels
    float exposeBlue = (1 + (.39 - input.TextureCoordinates.y) * 6); // some extra blue 

    // happens over full screen
    if (input.TextureCoordinates.y < 1.0f) {

        float redAdder = max(1, (exposeRed * (percentThroughDay/0.25f))); // be at full exposure at 25% of day gone
        float greenAdder = max(1, (exposeGreen * (percentThroughDay/0.25f))); // be at full exposure at 25% of day gone
        float blueAdder = max(1, (exposeBlue * (percentThroughDay/0.25f))); // be at full exposure at 25% of day gone

        // begin reducing adders
        if (percentThroughDay >= 0.25f && percentThroughDay < 0.50f) {
            redAdder = max(1, (exposeRed * (1-(percentThroughDay - 0.25f)/0.25f)));
            greenAdder = max(1, (exposeGreen * (1-(percentThroughDay - 0.25f)/0.25f)));
            blueAdder = max(1, (exposeGreen * (1-(percentThroughDay - 0.25f)/0.25f)));
        }

        //mid day
        else if (percentThroughDay >= 0.50f && percentThroughDay < 0.75f) {
            redAdder = 1;
            greenAdder = 1;
            blueAdder = 1;
        }

        // add adders back for sunset
        else if (percentThroughDay >= 0.75f && percentThroughDay < 0.85f) {
            redAdder = max(1, (exposeRed * ((percentThroughDay - 0.75f)/0.10f)));
            greenAdder = max(1, (exposeGreen * ((percentThroughDay - 0.75f)/0.10f)));
            blueAdder = max(1, (exposeBlue * ((percentThroughDay - 0.75f)/0.10f)));
        }

        // begin reducing adders
        else if (percentThroughDay >= 0.85f) {
            redAdder = max(1, (exposeRed * (1-(percentThroughDay - 0.85f)/0.15f)));
            greenAdder = max(1, (exposeGreen * (1-(percentThroughDay - 0.85f)/0.15f)));
            blueAdder = max(1, (exposeBlue * (1-(percentThroughDay - 0.85f)/0.15f)));
        }

        outputColor.r = outputColor.r * redAdder;
        outputColor.g = outputColor.g * greenAdder;
        outputColor.b = outputColor.b * blueAdder;
    }

    return outputColor;
}

technique ambientLightDayNight
{
    pass P0
    {
        PixelShader = compile ps_2_0 MainPS();
    }
};

这在很大程度上是我想要的（尽管它肯定可以使用一些计算优化）。

但是，我现在正在考虑在我的游戏中添加聚光灯以供玩家使用。我遵循了这种独立于环境光着色器工作的方法。这是一个使用 lightMask 的非常简单的着色器。

sampler s0;  

texture lightMask;  
sampler lightSampler = sampler_state{Texture = lightMask;};  

float4 PixelShaderLight(float2 coords: TEXCOORD0) : COLOR0  
{  
    float4 color = tex2D(s0, coords);  
    float4 lightColor = tex2D(lightSampler, coords);  
    return color * lightColor;  
}  


technique Technique1  
{  
    pass Pass1  
    {  
        PixelShader = compile ps_2_0 PixelShaderLight();  
    }  
}  

我的问题现在是同时使用这两个着色器。我目前的方法是将我的游戏场景绘制到渲染目标，应用环境光着色器，然后在应用聚光灯着色器的同时将游戏场景（现在使用环境光）绘制到客户端屏幕。

这带来了多个问题：

• 在环境光完全遮住灯光周围的任何东西后应用聚光灯着色器，而实际上灯光周围的区域应该是环境光。
• 聚光灯着色器中计算的光强度（光的亮度）在“夜晚”时过于暗淡，因为它是根据环境光着色器的输出计算光色。

我尝试在聚光灯着色器之后应用环境光着色器，但这只会将大部分内容渲染为黑色，因为环境光是针对大部分黑色背景计算的。

我已经尝试在聚光灯着色器中添加一些代码，将黑色像素着色为白色，以显示环境光背景，但是仍然根据较暗的环境光计算光强度 - 导致非常暗淡的光线。

另一个想法是修改我的环境光着色器以将 lightMask 作为参数，而不是将环境光应用于光罩上标记的灯光。然后我可以使用聚光灯着色器来应用光的渐变并修改颜色。但我不确定是否应该将这两个看似独立的灯光效果塞进一个像素着色器中。当我尝试这个时，我的着色器也没有编译，因为有太多的算术操作。

所以我想问大家的问题是：

• 我应该避免将多种效果塞进一个像素着色器中吗？
• 一般来说，我如何将聚光灯应用于可能是“黑暗”的环境光效果？

编辑

我的解决方案 - 最终没有使用聚光灯着色器，但仍然使用文章中给出的纹理绘制光蒙版，然后将该光蒙版传递给这个环境光着色器并抵消纹理渐变。

float4 MainPS(VertexShaderOutput input) : COLOR
{

    float4 constant = 1.5f;
    float4 pixelColor = tex2D(s0, input.TextureCoordinates);
    float4 outputColor = pixelColor;

    // lighting intensity is gradient of pixel position
    float Intensity = 1 + (1  - input.TextureCoordinates.y) * 1.05;
    outputColor.r = outputColor.r / ambient * Intensity;
    outputColor.g = outputColor.g / ambient * Intensity;
    outputColor.b = outputColor.b / ambient * Intensity;

    // sun set/rise blending  
    float gval = (1 - input.TextureCoordinates.y); // replace 1 with .39 to lock to 39 percent of screen (this is how it was before)
    float exposeRed = (1 + gval * 8); // overexpose red
    float exposeGreen = (1 + gval * 2); // some extra green
    float exposeBlue = (1 + gval * 4); // some extra blue 

    float quarterDayPercent = (percentThroughDay/0.25f);
    float redAdder = max(1, (exposeRed * quarterDayPercent)); // be at full exposure at 25% of day gone
    float greenAdder = max(1, (exposeGreen * quarterDayPercent)); // be at full exposure at 25% of day gone
    float blueAdder = max(1, (exposeBlue * quarterDayPercent)); // be at full exposure at 25% of day gone

    // begin reducing adders
    if (percentThroughDay >= 0.25f ) {
        float gradientVal1 = (1-(percentThroughDay - 0.25f)/0.25f);
        redAdder = max(1, (exposeRed * gradientVal1));
        greenAdder = max(1, (exposeGreen * gradientVal1));
        blueAdder = max(1, (exposeGreen * gradientVal1));
    }

    //mid day
    if (percentThroughDay >= 0.50f) {
        redAdder = 1;
        greenAdder = 1;
        blueAdder = 1;
    }

    // add adders back for sunset
    if (percentThroughDay >= 0.75f) {
        float gradientVal2 = ((percentThroughDay - 0.75f)/0.10f);
        redAdder = max(1, (exposeRed * gradientVal2));
        greenAdder = max(1, (exposeGreen * gradientVal2));
        blueAdder = max(1, (exposeBlue * gradientVal2));
    }

    // begin reducing adders
    if (percentThroughDay >= 0.85f) {

        float gradientVal3 = (1-(percentThroughDay - 0.85f)/0.15f);
        redAdder = max(1, (exposeRed * gradientVal3));
        greenAdder = max(1, (exposeGreen * gradientVal3));
        blueAdder = max(1, (exposeBlue * gradientVal3));
    }

    outputColor.r = outputColor.r * redAdder;
    outputColor.g = outputColor.g * greenAdder;
    outputColor.b = outputColor.b * blueAdder;

    // first check if we are in a lightMask light
    float4 lightMaskColor = tex2D(lightSampler, input.TextureCoordinates);
    if (lightMaskColor.r != 0.0f || lightMaskColor.g != 0.0f || lightMaskColor.b != 0.0f) 
    {
        // we are in the light so don't apply ambient light
        return pixelColor * (lightMaskColor + outputColor) * constant; // have to offset by outputColor here because the lightMask is pure black
    }

    return outputColor * pixelColor * constant; // must multiply by pixelColor here to offset the lightMask bounds. TODO: could try to restore original color by removing this multiplaction and factoring in more of an offset on ln 91
}