mirror of
https://github.com/hajimehoshi/ebiten.git
synced 2026-04-23 00:07:15 +08:00
Hajime Hoshi
4f6ca3e704
In general, floating point numbers cannot represent a precise real numbers. For example, even if a value 1.0/255.0 is multiplied by 255, the value might be slightly smaller than 1. In this case, casting this value to an integer can be 0 instead of 1. This change fixes this issue by introducing a round function. Updates #3270
149 lines
3.8 KiB
Go
149 lines
3.8 KiB
Go
// Copyright 2025 The Ebitengine Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package vector
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import (
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"github.com/hajimehoshi/ebiten/v2"
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)
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// The implementation is based on the following article:
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// https://medium.com/@evanwallace/easy-scalable-text-rendering-on-the-gpu-c3f4d782c5ac
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// These values are protected by cacheM.
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var (
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stencilBufferFillShader *ebiten.Shader
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stencilBufferBezierShader *ebiten.Shader
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stencilBufferNonZeroShader *ebiten.Shader
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stencilBufferNonZeroAAShader *ebiten.Shader
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stencilBufferEvenOddShader *ebiten.Shader
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stencilBufferEvenOddAAShader *ebiten.Shader
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)
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//ebitengine:shadersource
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const stencilBufferFillShaderSrc = `//kage:unit pixels
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package main
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func Fragment(dstPos vec4, srcPos vec2, color vec4, custom vec4) vec4 {
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v := 1.0 / 255.0
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if frontfacing() {
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v *= 16
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}
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return v * color
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}
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`
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//ebitengine:shadersource
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const stencilBufferBezierShaderSrc = `//kage:unit pixels
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package main
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func Fragment(dstPos vec4, srcPos vec2, color vec4, custom vec4) vec4 {
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// Loop-Blinn algorithm.
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// https://developer.nvidia.com/gpugems/gpugems3/part-iv-image-effects/chapter-25-rendering-vector-art-gpu
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uv := custom.xy
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v := clamp(-sign(uv.x * uv.x - uv.y), 0, 1) * 1.0/255.0
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// This is opposite to the fill shader, especially for the non-zero fill rule.
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if !frontfacing() {
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v *= 16
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}
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return v * color
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}
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`
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//ebitengine:shadersource
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const stencilBufferNonZeroShaderSrc = `//kage:unit pixels
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package main
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func round(x float) float {
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return floor(x + 0.5)
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}
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func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
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c := imageSrc0UnsafeAt(srcPos)
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r := int(round(c.r*255))
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w := abs((r >> 4) - (r & 0x0F))
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v := min(float(w), 1)
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return v * color
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}
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`
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//ebitengine:shadersource
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const stencilBufferNonZeroAAShaderSrc = `//kage:unit pixels
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package main
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func round(x vec4) vec4 {
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return floor(x + 0.5)
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}
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func Fragment(dstPos vec4, srcPos vec2, color vec4, custom vec4) vec4 {
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c0 := imageSrc0UnsafeAt(srcPos)
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// imageSrc1UnsafeAt uses the offset info, which would prevent batching.
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// Use a custom offset instead.
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c1 := imageSrc0UnsafeAt(srcPos + custom.xy)
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ci0 := ivec4(round(c0*255))
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ci1 := ivec4(round(c1*255))
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w0 := abs((ci0 >> 4) - (ci0 & 0x0F))
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w1 := abs((ci1 >> 4) - (ci1 & 0x0F))
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v0 := min(vec4(w0), 1)
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v1 := min(vec4(w1), 1)
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return (dot(v0, vec4(1.0/8.0)) + dot(v1, vec4(1.0/8.0))) * color
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}
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`
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//ebitengine:shadersource
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const stencilBufferEvenOddShaderSrc = `//kage:unit pixels
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package main
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func round(x float) float {
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return floor(x + 0.5)
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}
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func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
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c := imageSrc0UnsafeAt(srcPos)
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r := int(round(c.r*255))
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v := abs((r >> 4) - (r & 0x0F))
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return float(v % 2) * color
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}
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`
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//ebitengine:shadersource
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const stencilBufferEvenOddAAShaderSrc = `//kage:unit pixels
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package main
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func round(x vec4) vec4 {
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return floor(x + 0.5)
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}
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func Fragment(dstPos vec4, srcPos vec2, color vec4, custom vec4) vec4 {
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c0 := imageSrc0UnsafeAt(srcPos)
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// imageSrc1UnsafeAt uses the offset info, which would prevent batching.
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// Use a custom offset instead.
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c1 := imageSrc0UnsafeAt(srcPos + custom.xy)
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ci0 := ivec4(round(c0*255))
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ci1 := ivec4(round(c1*255))
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w0 := abs((ci0 >> 4) - (ci0 & 0x0F))
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w1 := abs((ci1 >> 4) - (ci1 & 0x0F))
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v0 := vec4(w0 % 2)
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v1 := vec4(w1 % 2)
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return (dot(v0, vec4(1.0/8.0)) + dot(v1, vec4(1.0/8.0))) * color
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}
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`
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