代码之家 › 专栏 › 技术社区 › Roi Mulia

与OpenGL mix相当的金属

metal shader opengl swift ios

Roi Mulia · 技术社区 · 7 年前

我在试着理解什么是等价物 mix OpenGL OpenGL 我试图转换的代码:

float udRoundBox( vec2 p, vec2 b, float r )
{
    return length(max(abs(p)-b+r,0.0))-r;
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    // setup
    float t = 0.2 + 0.2 * sin(mod(iTime, 2.0 * PI) - 0.5 * PI);
    float iRadius = min(iResolution.x, iResolution.y) * (0.05 + t);
    vec2 halfRes = 0.5 * iResolution.xy;

    // compute box
    float b = udRoundBox( fragCoord.xy - halfRes, halfRes, iRadius );

    // colorize (red / black )
    vec3 c = mix( vec3(1.0,0.0,0.0), vec3(0.0,0.0,0.0), smoothstep(0.0,1.0,b) );

    fragColor = vec4( c, 1.0 );
}

到目前为止,我能够转换其中的一部分:

float udRoundBox( float2 p, float2 b, float r )
{
    return length(max(abs(p)-b+r,0.0))-r;
}

float4 cornerRadius(sampler_h src) {

    float2 greenCoord = src.coord(); // this is alreay in relative coords; no need to devide by image size

    float t = 0.5;
    float iRadius = min(greenCoord.x, greenCoord.y) * (t);
    float2 halfRes = float2(greenCoord.x * 0.5, greenCoord.y * 0.5);

    float b = udRoundBox( float2(greenCoord.x - halfRes.x, greenCoord.y - halfRes.y), halfRes, iRadius );

    float3 c = mix(float3(1.0,0.0,0.0), float3(0.0,0.0,0.0), smoothstep(0.0,1.0,b) );

    return float4(c, 1.0);
}

但它正在生产绿色屏幕。我试图在视频中实现拐角半径,如下所示:

0 回复 | 直到 7 年前

Frank Rupprecht 7 年前

问题是 greenCoord 当前像素 与绝对输入分辨率无关。

如果您想更换您的 iResolution 使用 src.size() 相反

destination 参数设置为内核的输入,如下所示:

float4 cornerRadius(sampler src, destination dest) {
    const float2 destCoord = dest.coord(); // pixel position in the output buffer in absolute coordinates
    const float2 srcSize = src.size();

    const float t = 0.5;
    const float radius = min(srcSize.x, srcSize.y) * t;
    const float2 halfRes = 0.5 * srcSize;

    const float b = udRoundBox(destCoord - halfRes, halfRes, radius);

    const float3 c = mix(float3(1.0,0.0,0.0), float3(0.0,0.0,0.0), smoothstep(0.0,1.0,b) );

    return float4(c, 1.0);
}