ebiten/examples/flappy/crt.go

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// Copyright 2022 The Ebitengine Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//go:build ignore
// Reference: a public domain CRT effect
// https://github.com/libretro/glsl-shaders/blob/master/crt/shaders/crt-lottes.glsl
package main
func Warp(pos vec2) vec2 {
const (
warpX = 0.031
warpY = 0.041
)
pos = pos*2 - 1
pos *= vec2(1+(pos.y*pos.y)*warpX, 1+(pos.x*pos.x)*warpY)
return pos/2 + 0.5
}
func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
// Adjust the texture position to [0, 1].
pos := texCoord
origin, size := imageSrcRegionOnTexture()
pos -= origin
pos /= size
pos = Warp(pos)
return imageSrc0At(pos*size + origin)
}