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internal/ui: simplify the screen shader

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This commit is contained in:
Hajime Hoshi 2022-08-26 19:01:59 +09:00
parent 5bb70f485e
commit 7c55065490
1 changed files with 10 additions and 2 deletions
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12
internal/ui/context.go
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@ -36,6 +36,7 @@ var Scale float
func Fragment(position vec4, texCoord vec2, color vec4) vec4 { func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
sourceSize := imageSrcTextureSize() sourceSize := imageSrcTextureSize()
// texelSize is one pixel size in texel sizes.
texelSize := 1 / sourceSize texelSize := 1 / sourceSize
halfScaledTexelSize := texelSize / 2 / Scale halfScaledTexelSize := texelSize / 2 / Scale
@ -51,8 +52,15 @@ func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
c2 := imageSrc0UnsafeAt(vec2(p0.x, p1.y)) c2 := imageSrc0UnsafeAt(vec2(p0.x, p1.y))
c3 := imageSrc0UnsafeAt(p1) c3 := imageSrc0UnsafeAt(p1)
rateCenter := vec2(1, 1) - halfScaledTexelSize // p is the p1 value in one pixel assuming that the pixel's upper-left is (0, 0) and the lower-right is (1, 1).
rate := clamp(((fract(p0 * sourceSize) - rateCenter) * Scale) + rateCenter, 0, 1) p := fract(p1 * sourceSize)
// rate indicates how much the 4 colors are mixed. rate is in between [0, 1].
//
// 0 <= p < 1/Scale: The rate is in between [0, 1)
// 1/Scale <= p: Don't care. Adjacent colors (e.g. c0 vs c1 in an X direction) should be the same.
rate := clamp(p*Scale, 0, 1)
return mix(mix(c0, c1, rate.x), mix(c2, c3, rate.x), rate.y) return mix(mix(c0, c1, rate.x), mix(c2, c3, rate.x), rate.y)
} }
` `