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[app] Fix up the alpha feathering

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This commit is contained in:
Eryn Wells 2017-08-09 08:55:28 -07:00
parent 99fe2147ad
commit f95ddd4f5c
1 changed files with 18 additions and 11 deletions
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29
Metaballs/Shaders.metal
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@ -65,8 +65,8 @@ passthroughVertexShader(uint vid [[vertex_id]],
float sampleAtPoint(float2, constant Ball*, int); float sampleAtPoint(float2, constant Ball*, int);
// Color samplers // Color samplers
float4 singleColor(float, float4); float4 singleColor(float, float, float4);
float4 gradient2(float, float, float4, float4); float4 gradient2(float, float, float, float4, float4);
// Helpers // Helpers
float mapValueFromRangeOntoRange(float, float, float, float, float); float mapValueFromRangeOntoRange(float, float, float, float, float);
@ -77,24 +77,20 @@ sampleToColorShader(RasterizerData in [[stage_in]],
constant Parameters& parameters [[buffer(0)]], constant Parameters& parameters [[buffer(0)]],
constant Ball* balls [[buffer(1)]]) constant Ball* balls [[buffer(1)]])
{ {
const float target = 1.0;
const float sample = sampleAtPoint(in.position.xy, balls, parameters.numberOfBalls); const float sample = sampleAtPoint(in.position.xy, balls, parameters.numberOfBalls);
const float blend = in.position.x / parameters.size.x; const float blend = in.position.x / parameters.size.x;
float4 out; float4 out;
switch (parameters.colorStyle) { switch (parameters.colorStyle) {
case SingleColor: case SingleColor:
out = singleColor(sample, parameters.colors[0]); out = singleColor(sample, target, parameters.colors[0]);
break; break;
case Gradient2Horizontal: case Gradient2Horizontal:
out = gradient2(sample, blend, parameters.colors[0], parameters.colors[1]); out = gradient2(sample, target, blend, parameters.colors[0], parameters.colors[1]);
break; break;
} }
// Feather the alpha.
const float target = 1.0;
const float a = clamp(mapValueFromRangeOntoRange(sample, 0.75 * target, target, 0, 1), 0.0, 1.0);
out.w = a;
return out; return out;
} }
@ -116,19 +112,30 @@ sampleAtPoint(float2 point,
float4 float4
singleColor(float sample, singleColor(float sample,
float target,
float4 color) float4 color)
{ {
return sample > 1.0 ? color : float4(); float4 out;
if (sample > 1.0) {
out = color;
}
// Feather the alpha value.
const float a = clamp(mapValueFromRangeOntoRange(sample, 0.75 * target, target, 0, 1), 0.0, 1.0);
out = float4(out.xyz, a);
return out;
} }
float4 float4
gradient2(float sample, gradient2(float sample,
float target,
float normalizedBlend, float normalizedBlend,
float4 fromColor, float4 fromColor,
float4 toColor) float4 toColor)
{ {
float4 blendedColor = averageTwoColors(normalizedBlend, fromColor, toColor); float4 blendedColor = averageTwoColors(normalizedBlend, fromColor, toColor);
float4 out = singleColor(sample, blendedColor); float4 out = singleColor(sample, target, blendedColor);
return out; return out;
} }